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COMPOSITES
MANUFACTURING
Materials, Product,
and Process Engineering
© 2002 by CRC Press LLC
CRC PR ESS
Boca Raton London New York Washington, D.C.
COMPOSITES
MANUFACTURING
Materials, Product,
and Process Engineering
Sanjay K. Mazumdar, Ph.D.

This book contains information obtained from authentic and highly regarded sources. Reprinted material
is quoted with permission, and sources are indicated. A wide variety of references are listed. Reasonable
efforts have been made to publish reliable data and information, but the author and the publisher cannot
assume responsibility for the validity of all materials or for the consequences of their use.
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Visit the CRC Press Web site at www.crcpress.com

© 2002 by CRC Press LLC
No claim to original U.S. Government works
International Standard Book Number 0-8493-0585-3
Library of Congress Card Number 2001004994
Printed in the United States of America 1 2 3 4 5 6 7 8 9 0
Printed on acid-free paper

Library of Congress Cataloging-in-Publication Data

Mazumdar, Sanjay K.
Composites manufacturing : materials, product, and process
engineering / by Sandjay K. Mazumdar.
p. cm.
Includes bibliographical references and index.
ISBN 0-8493-0585-3
1. Composite materials.
TA418.9.C6 M34 2001
620.1

18--dc21 2001004994

Surrendered to the Lord of the Universe

Preface

Early large-scale commercial applications of composite materials started
during World War II (late 1940s and early 1950s) with marine applications
for the military; but today, composite products are manufactured by a diverse
range of industries, including aerospace, automotive, marine, boating, sport-
ing goods, consumer, infrastructure, and more. In recent years, the develop-
ment of new and improved composites manufacturing processes has caused
unlimited product development opportunities. New high-volume produc-
tion methods such as compression molding (SMC) reveal a gained maturity
level and are routinely used for making automotive, consumer, and indus-
trial parts with a good confidence level. The use of composite materials is
no longer limited to only naval and spacecraft applications. New material
innovations, and a drop in pricing and development of improved manufac-
turing processes have given rise to the presence of composite materials in
almost every industrial sector. In fact, because of styling detail possibilities
and the high surface finish quality attainable by composites fabrication pro-
cesses, composites are considered materials of choice for certain industry
sectors (e.g., automotive).
Until recently, only a few universities offered courses on composites man-
ufacturing, probably due to the lack of a suitable textbook. This book offers
all the related materials to make composites manufacturing a part of the
curriculum in the composite materials discipline. This book covers important
aspects of composites product manufacturing, such as product manufactur-
ability, product development, processing science, manufacturing processes,
cost estimating, and more. These aspects of fabrication issues, which are
crucial in the production of good composite parts, have not been covered in
any of the books available in the composites industry. The most common
courses offered at universities in the composite materials field are related to
the introduction and design aspects of composite materials. Without pro-
cessing and product development knowledge, successful composite prod-
ucts cannot be fabricated. This book bridges this gap and covers important
elements of product manufacturing using composite materials. This book is
suitable for students, engineers, and researchers working in the composite
materials field. This book offers valuable insight into the production of cost-
competitive and high-quality composite parts. Engineers and professionals
working in the composites industry can significantly benefit from the content
of this book.
This book discusses the subject of manufacturing within the framework
of the fundamental classification of processes. This should help the reader
understand where a particular manufacturing process fits within the overall

fabrication scheme and what processes might be suitable for the manufacture
of a particular component. The subject matters are adequately descriptive
for those unfamiliar with the various fabrication techniques and yet suffi-
ciently analytical for an academic course in composites manufacturing.
The book takes the reader step-by-step from raw material selection to final
part fabrication and recycling. Chapter 2 details the raw materials available
in the composites industry for the fabrication of various composite products.
Methods of selecting the correct material from the thousands of materials
available are discussed in Chapter 3. Chapter 4 discusses the six important
phases of the product development process. It provides roadmaps to engi-
neers and team members for the activities and deliverables required for the
design, development, and fabrication of the part. Chapter 5 describes pro-
cedures to design a product, taking manufacturing into consideration. To be
competitive in the current global marketplace, products must be designed
in a minimum amount of time and with minimum resources and cost. Design
for manufacturing (DFM) plays a key role in concept generation, concept
approval, and concept improvement, and comes up with a better design in
the shortest time. It integrates processing knowledge into the design of a
part to get the maximum benefit and capabilities from the manufacturing
method. As compared to metals, composite materials offer the higher poten-
tial of utilizing DFM and part integration, and therefore can significantly
reduce the cost of production. Chapter 6 discusses various composite man-
ufacturing techniques in terms of their advantages, disadvantages, raw mate-
rials requirements, applications, tooling and mold requirements, methods of
applying heat and pressure, processing steps, and more. Process selection
criteria and basic steps in composite manufacturing processes are discussed
in this chapter. Process models for key manufacturing processes are
described in Chapter 7. Process models are used to determine optimum
processing conditions for making good-quality composite parts. This elimi-
nates processing problems before a manufacturing process begins or before
the part design is finalized. Preproduction guidelines and methods of writing
manufacturing instructions and bill of materials are discussed in Chapter 8.
Joining and machining of composite parts require a different approach than
the joining and machining of metal parts; these are discussed in Chapters 9
and 10, respectively. Cost-estimating techniques are elaborated in Chapter 11.
Tools for selecting a best technology/fabrication process to get a competitive
advantage in the marketplace are included in this chapter. Finally, recycling
aspects of
composite materials, which are becoming growing concerns in
industry and government sectors, are discussed in Chapter 12. Overall, this
book provides professionals with valuable information related to composites
product manufacturing as well as best state-of-the-art knowledge in this
field.

Acknowledgments

With great devotion I acknowledge the grace of God for the successful
completion of this book.
I am grateful to all the engineers, researchers, scientists, and professionals
who contributed to the development of composites manufacturing processes
and technologies. With their efforts, composites technology has gained matu-
rity and has been used confidently for various applications. I am thankful
to Professor Timothy Gutowski (M.I.T.), Gerald Sutton (Intellitec), John
Marks (COI Materials), and John Taylor (Goodrich Corp.) for reviewing this
book and for providing excellent comments.
I am thankful to my friends and relatives for their kindness and support.
I am grateful to my wife Gargi Mazumdar for her patience and support
during the writing of this book. Thanks to my 6-year-old daughter Ria
Mazumdar for letting me work on my book. And I am thankful to my parents
for their love and support.

Author

Dr. Sanjay K. Mazumdar

is president and CEO of E-Composites.com, Inc.,
Grandville, Michigan, U.S.A., a leading service-oriented company providing
market reports, job bank services,

CompositesWeek

newsletter, CompositesEx-
change for buy and sell trades, product marketing, product commercializa-
tion, and various other services for the composite materials industry. E-
Composites.com, Inc. provides various platforms for connecting buyers to
sellers, vendors to customers, employers to employees, and technical pro-
fessionals to a wealth of information. E-Composites.com, Inc. is dedicated
to rapid development of the composite materials industry and connects more
than 20,000 composite users and suppliers from more than 50 countries using
its weekly newsletter and Web site. E-Composites.com, Inc.’s clients range
from small to Fortune 500 companies such as AOC, BFGoodrich, Bayer Corp.,
Dow Corning, General Electric, Hexcel, Johns Manville, Lockheed Martin,
Owens Corning, Saint-Gobain, Zeon Chemical, and many more.
Dr. Mazumdar has published more than 25 professional papers on pro-
cessing, joining, and testing of composite materials in reputed international
journals and conference proceedings. He has designed and developed more
than 100 composite products for a variety of applications, including auto-
motive, aerospace, electronic, consumer, and industrial applications. He has
two Society of Plastics Engineers (SPE) awards and two General Motors’
Record of Innovation awards for his creativity and innovations. He has
worked as adjunct faculty at the University of Michigan, Dearborn, and
Concordia University, Montreal, and has taught composite materials-related
courses to undergraduate and graduate students. He has given seminars and
presentations at international conferences and reputed universities, includ-
ing the University of California, Berkeley, and Fortune 500 companies.
Dr. Mazumdar can be contacted by e-mail at Sanjaym@e-composites.com

visit the Web site — www.e-composites.com — for details.

Contents

Introduction

1.1 Conventional Engineering Materials
1.1.1 Metals
1.1.2 Plastics
1.1.3 Ceramics
1.1.4 Composites
1.2 What Are Composites?
1.3 Functions of Fibers and Matrix
1.4 Special Features of Composites
1.5 Drawbacks of Composites
1.6 Composites Processing
1.7 Composites Product Fabrication
1.8 Composites Markets
1.8.1 The Aerospace Industry
1.8.2 The Automotive Industry
1.8.3 The Sporting Goods Industry
1.8.4 Marine Applications
1.8.5 Consumer Goods
1.8.6 Construction and Civil Structures
1.8.7 Industrial Applications
1.9 Barriers in Composite Markets
References
Questions

Raw Materials for Part Fabrication

2.1 Introduction
2.2 Reinforcements
2.2.1 Glass Fiber Manufacturing
2.2.2 Carbon Fiber Manufacturing
2.2.3 Aramid Fiber Manufacturing
2.3 Matrix Materials
2.3.1 Thermoset Resins
2.3.1.1 Epoxy
2.3.1.2 Phenolics
2.3.1.3 Polyesters
2.3.1.4 Vinylesters
2.3.1.5 Cyanate Esters
2.3.1.6 Bismaleimide (BMI) and Polyimide
2.3.1.7 Polyurethane

2.3.2 Thermoplastic Resins
2.3.2.1 Nylons
2.3.2.2 Polypropylene (PP)
2.3.2.3 Polyetheretherketone (PEEK)
2.3.2.4 Polyphenylene Sulfide (PPS)
2.4 Fabrics
2.4.1 Woven Fabrics
2.4.2 Noncrimp Fabrics
2.5 Prepregs
2.5.1 Thermoset Prepregs
2.5.2 Thermoplastic Prepregs
2.6 Preforms
2.7 Molding Compound
2.7.1 Sheet Molding Compound
2.7.2 Thick Molding Compound (TMC)
2.7.3 Bulk Molding Compound (BMC)
2.7.4 Injection Moldable Compounds
2.8 Honeycomb and Other Core Materials
References
Questions

Material Selection Guidelines

3.1 Introduction
3.2 The Need for Material Selection
3.3 Reasons for Material Selection
3.4 Material Property Information
3.5 Steps in the Material Selection Process
3.5.1 Understanding and Determining the Requirements
3.5.2 Selection of Possible Materials
3.5.3 Determination of Candidate Materials
3.5.4 Testing and Evaluation
3.6 Material Selection Methods
3.6.1 Cost vs. Property Analysis
3.6.2 Weighted Property Comparison Method
3.6.2.1 Scaling for Maximum Property Requirement
3.6.2.2 Scaling for Minimum Property Requirement
3.6.2.3 Scaling for Nonquantitative Property
3.6.3 Expert System for Material Selection
Bibliography
Questions

Product Development

4.1 Introduction
4.2 What Is the Product Development Process
4.3 Reasons for Product Development
4.4 Importance of Product Development

4.5 Concurrent Engineering
4.6 Product Life Cycle
4.7 Phases of Product Development
4.7.1 Concept Feasibility Phase
4.7.2 Detailed Design Phase
4.7.3 Prototype Development and Testing Phase
4.7.4 Preproduction Demonstration, or Pilot-Scale Production
4.7.5 Full-Scale Production and Distribution
4.7.6 Continuous Improvement
4.8 Design Review
4.9 Failure Modes and Effects Analysis (FMEA)
Reference
Bibiliography
Questions

Design for Manufacturing

5.1 Introduction
5.2 Design Problems
5.3 What Is DFM?
5.4 DFM Implementation Guidelines
5.4.1 Minimize Part Counts
5.4.2 Eliminate Threaded Fasteners
5.4.3 Minimize Variations
5.4.4 Easy Serviceability and Maintainability
5.4.5 Minimize Assembly Directions
5.4.6 Provide Easy Insertion and Alignment
5.4.7 Consider Ease for Handling
5.4.8 Design for Multifunctionality
5.4.9 Design for Ease of Fabrication
5.4.10 Prefer Modular Design
5.5 Success Stories
5.5.1 Composite Pickup Box
5.5.2 Laser Printer
5.5.3 Black & Decker Products
5.6 When to Apply DFM
5.7 Design Evaluation Method
5.8 Design for Assembly (DFA)
5.8.1 Benefits of DFA
5.8.2 Assembly-Related Defects
5.8.3 Guidelines for Minimizing Assembly Defects
References
Questions

Manufacturing Techniques

6.1 Introduction

6.2 Manufacturing Process Selection Criteria
6.2.1 Production Rate/Speed
6.2.2 Cost
6.2.3 Performance
6.2.4 Size
6.2.5 Shape
6.3 Product Fabrication Needs
6.4 Mold and Tool Making
6.4.1 Mold Design Criteria
6.4.1.1 Shrinkage Allowance
6.4.1.2 Coefficient of Thermal Expansion of Tool
Material and End Product
6.4.1.3 Stiffness of the Mold
6.4.1.4 Surface Finish Quality
6.4.1.5 Draft and Corner Radii
6.4.2 Methods of Making Tools
6.4.2.1 Machining
6.4.2.2 FRP Tooling for Open Molding Processes
6.4.3 Tooling Guidelines for Closed Molding Operations
6.5 Basic Steps in a Composites Manufacturing
Process
6.5.1 Impregnation
6.5.2 Lay-up
6.5.3 Consolidation
6.5.4 Solidification
6.6 Advantages and Disadvantages of Thermoset
and Thermoplastic Composites Processing
6.6.1 Advantages of Thermoset Composites Processing
6.6.2 Disadvantages of Thermoset Composites Processing
6.6.3 Advantages of Thermoplastic Composites Processing
6.6.4 Disadvantages of Thermoplastic Composites Processing
6.7 Composites Manufacturing Processes
6.8 Manufacturing Processes for Thermoset Composites
6.8.1 Prepreg Lay-Up Process
6.8.1.1 Major Applications
6.8.1.2 Basic Raw Materials
6.8.1.3 Tooling Requirements
6.8.1.4 Making of the Part
6.8.1.5 Methods of Applying Heat and Pressure
6.8.1.6 Basic Processing Steps
6.8.1.7 Typical Manufacturing Challenges
6.8.1.8 Advantages of the Prepreg Lay-Up Process
6.8.1.9 Limitations of the Prepreg Lay-Up Process
6.8.2 Wet Lay-Up Process
6.8.2.1 Major Applications
6.8.2.2 Basic Raw Materials
6.8.2.3 Tooling Requirements

6.8.2.4 Making of the Part
6.8.2.5 Methods of Applying Heat and Pressure
6.8.2.6 Basic Processing Steps
6.8.2.7 Advantages of the Wet Lay-Up Process
6.8.2.8 Limitations of the Wet Lay-Up Process
6.8.3 Spray-Up Process
6.8.3.1 Major Applications
6.8.3.2 Basic Raw Materials
6.8.3.3 Tooling Requirements
6.8.3.4 Making of the Part
6.8.3.5 Methods of Applying Heat and Pressure
6.8.3.6 Basic Processing Steps
6.8.3.7 Advantages of the Spray-Up Process
6.8.3.8 Limitations of the Spray-Up Process
6.8.4 Filament Winding Process
6.8.4.1 Major Applications
6.8.4.2 Basic Raw Materials
6.8.4.3 Tooling
6.8.4.4 Making of the Part
6.8.4.5 Methods of Applying Heat and Pressure
6.8.4.6 Methods of Generating the Desired Winding
Angle
6.8.4.7 Basic Processing Steps
6.8.4.8 Advantages of the Filament Winding Process
6.8.4.9 Limitations of the Filament Winding Process
6.8.5 Pultrusion Process
6.8.5.1 Major Applications
6.8.5.2 Basic Raw Materials
6.8.5.3 Tooling
6.8.5.4 Making of the Part
6.8.5.4.1 Wall Thickness
6.8.5.4.2 Corner Design
6.8.5.4.3 Tolerances, Flatness, and Straightness
6.8.5.4.4 Surface Texture
6.8.5.5 Methods of Applying Heat and Pressure
6.8.5.6 Basic Processing Steps
6.8.5.7 Advantages of the Pultrusion Process
6.8.5.8 Limitations of the Pultrusion Process
6.8.6 Resin Transfer Molding Process
6.8.6.1 Major Applications
6.8.6.2 Basic Raw Materials
6.8.6.3 Tooling
6.8.6.4 Making of the Part
6.8.6.5 Methods of Applying Heat and Pressure
6.8.6.6 Basic Processing Steps
6.8.6.7 Advantages of the Resin Transfer Molding
Process

6.8.6.8 Limitations of the Resin Transfer Molding
Process
6.8.6.9 Variations of the RTM Process
6.8.6.9.1 VARTM
6.8.6.9.2 SCRIMP
6.8.7 Structural Reaction Injection Molding (SRIM) Process
6.8.7.1 Major Applications
6.8.7.2 Basic Raw Materials
6.8.7.3 Tooling
6.8.7.4 Making of the Part
6.8.7.5 Methods of Applying Heat and Pressure
6.8.7.6 Basic Processing Steps
6.8.7.7 Advantages of the SRIM Process
6.8.7.8 Limitations of the SRIM Process
6.8.8 Compression Molding Process
6.8.8.1 Major Applications
6.8.8.2 Basic Raw Materials
6.8.8.3 Making of the Part
6.8.8.4 Mold Design
6.8.8.5 Methods of Applying Heat and Pressure
6.8.8.6 Basic Processing Steps
6.8.8.7 Advantages of the Compression Molding
Process
6.8.8.8 Limitations of the Compression Molding
Process
6.8.9 Roll Wrapping Process
6.8.9.1 Major Applications
6.8.9.2 Basic Raw Materials
6.8.9.3 Tooling
6.8.9.4 Making of the Part
6.8.9.5 Methods of Applying Heat and Pressure
6.8.9.6 Basic Processing Steps
6.8.9.7 Advantages of the Roll Wrapping Process
6.8.9.8 Limitations of the Roll Wrapping Process
6.8.9.9 Common Problems with the Roll Wrapping
Process
6.8.10 Injection Molding of Thermoset Composites
6.8.10.1 Major Applications
6.8.10.2 Basic Raw Materials
6.8.10.3 Tooling
6.8.10.4 Making of the Part
6.9 Manufacturing Processes for Thermoplastic Composites
6.9.1 Thermoplastic Tape Winding
6.9.1.1 Major Applications
6.9.1.2 Basic Raw Materials
6.9.1.3 Tooling

6.9.1.4 Making of the Part
6.9.1.5 Methods of Applying Heat and Pressure
6.9.1.6 Advantages of the Thermoplastic Tape Winding
Process
6.9.1.7 Limitations of the Thermoplastic Tape Winding
Process
6.9.2 Thermoplastic Pultrusion Process
6.9.2.1 Major Applications
6.9.2.2 Basic Raw Materials
6.9.2.3 Tooling
6.9.2.4 Making of the Part
6.9.2.5 Methods of Applying Heat and Pressure
6.9.2.6 Advantages of the Thermoplastic Pultrusion
Process
6.9.2.7 Limitations of the Thermoplastic Pultrusion
Process
6.9.3 Compression Molding of GMT
6.9.3.1 Major Applications
6.9.3.2 Basic Raw Materials
6.9.3.3 Tooling
6.9.3.4 Part Fabrication
6.9.3.5 Methods of Applying Heat and Pressure
6.9.3.6 Advantages of Compression Molding of GMT
6.9.3.7 Limitations of Compression Molding of GMT
6.9.4 Hot Press Technique
6.9.4.1 Major Applications
6.9.4.2 Basic Raw Materials
6.9.4.3 Tooling
6.9.4.4 Making of the Part
6.9.4.5 Methods of Applying Heat and Pressure
6.9.4.6 Basic Processing Steps
6.9.4.7 Advantages of the Hot Press Technique
6.9.4.8 Limitations of the Hot Press Technique
6.9.5 Autoclave Processing
6.9.5.1 Major Applications
6.9.5.2 Basic Raw Materials
6.9.5.3 Tooling
6.9.5.4 Making the Part
6.9.5.5 Methods of Applying Heat and Pressure
6.9.5.6 Basic Processing Steps
6.9.5.7 Advantages of Autoclave Processing
6.9.5.8 Limitations of Autoclave Processing
6.9.6 Diaphragm Forming Process
6.9.6.1 Major Applications
6.9.6.2 Basic Raw Materials
6.9.6.3 Tooling

6.9.6.4 Making of the Part
6.9.6.5 Methods of Applying Heat and Pressure
6.9.6.6 Advantages of the Diaphragm Forming Process
6.9.6.7 Limitations of the Diaphragm Forming Process
6.9.7 Injection Molding
6.9.7.1 Major Applications
6.9.7.2 Basic Raw Materials
6.9.7.3 Tooling
6.9.7.4 Making of the Part
6.9.7.5 Basic Processing Steps
6.9.7.6 Methods of Applying Heat and Pressure
6.9.7.7 Advantages of the Injection Molding Process
6.9.7.8 Limitations of the Injection Molding Process
References
Bibliography
Questions

Process Models

7.1 Introduction
7.2 The Importance of Models in Composites Manufacturing
7.3 Composites Processing
7.4 Process Models for Selected Thermosets and Thermoplastics
Processing
7.4.1 Thermochemical Sub-Model
7.4.1.1 Autoclave or Hot Press Process for Thermoset
Composites
7.4.1.2 Filament Winding of Thermoset Composites
7.4.1.3 Tape Winding of Thermoplastic Composites
7.4.2 Flow Sub-Model
7.4.2.1 Compaction and Resin Flow during Autoclave
Cure
7.4.2.1.1 Resin Flow Normal to the Tool Plate
7.4.2.1.2 Resin Flow Parallel to the Tool Plate
7.4.2.1.3 Total Resin Flow
7.4.2.2 Compaction and Resin Flow during Filament
Winding
7.4.2.3 Consolidation of Thermoplastic Composites
during Autoclave or Hot Press Processing
7.4.2.4 Consolidation and Bonding Models for
Thermoplastic Tape Laying and Tape Winding
7.4.3 Void Sub-Model
7.4.4 Stress Sub-Model
7.5 Process Model for RTM
References
Questions

Production Planning and Manufacturing Instructions

8.1 Introduction
8.2 Objectives of Production Planning
8.3 Bill of Materials
8.4 Manufacturing Instructions
8.4.1 Manufacturing Instructions for Making Tooling Panels
8.4.2 Manufacturing Instructions for Making Flaps
8.5 Capacity Planning
8.5.1 Problem Definition
8.5.2 Assumptions
8.5.3 Capacity Analysis
8.5.3.1 Autoclave Capacity Analysis
8.5.3.2 Freezer Storage Requirement
Questions

Joining of Composite Materials

9.1 Introduction
9.2 Adhesive Bonding
9.2.1 Failure Modes in Adhesive Bonding
9.2.2 Basic Science of Adhesive Bonding
9.2.2.1 Adsorption Theory
9.2.2.2 Mechanical Theory
9.2.2.3 Electrostatic and Diffusion Theories
9.2.3 Types of Adhesives
9.2.3.1 Two-Component Mix Adhesives
9.2.3.1.1 Epoxy Adhesives
9.2.3.1.2 Polyurethane Adhesives
9.2.3.2 Two-Component, No-Mix Adhesives
9.2.3.2.1 Acrylic Adhesives
9.2.3.2.2 Urethane Methacrylate Ester
(Anaerobic) Adhesives
9.2.3.3 One-Component, No-Mix Adhesives
9.2.3.3.1 Epoxies
9.2.3.3.2 Polyurethanes
9.2.3.3.3 Cyanoacrylates
9.2.3.3.4 Hot-Melt Adhesives
9.2.3.3.5 Solvent- or Water-Based Adhesives
9.2.4 Advantages of Adhesive Bonding over Mechanical Joints
9.2.5 Disadvantages of Adhesive Bonding
9.2.6 Adhesive Selection Guidelines
9.2.7 Surface Preparation Guidelines
9.2.7.1 Degreasing
9.2.7.2 Mechanical Abrasion
9.2.7.3 Chemical Treatment
9.2.8 Design Guidelines for Adhesive Bonding

9.2.9 Theoretical Stress Analysis for Bonded Joints
9.3 Mechanical Joints
9.3.1 Advantages of Mechanical Joints
9.3.2 Disadvantages of Mechanical Joints
9.3.3 Failure Modes in a Bolted Joint
9.3.4 Design Parameters for Bolted Joints
9.3.5 Preparation for the Bolted Joint
References
Questions

Machining and Cutting of Composites

10.1 Introduction
10.2 Objectives/Purposes of Machining
10.3 Challenges during Machining of Composites
10.4 Failure Mode during Machining of Composites
10.5 Cutting Tools
10.6 Types of Machining Operations
10.6.1 Cutting Operation
10.6.1.1 Waterjet Cutting
10.6.1.2 Laser Cutting
10.6.2 Drilling Operation
References
Questions

Cost Estimation

11.1 Introduction
11.2 The Need for Cost Estimating
11.3 Cost Estimating Requirements
11.4 Types of Cost
11.4.1 Nonrecurring (Fixed) Costs
11.4.2 Recurring (Variable) Costs
11.5 Cost Estimating Techniques
11.5.1 Industrial Engineering Approach (Methods Engineering)
11.5.2 ACCEM Cost Model
11.5.3 First-Order Model
11.5.4 Cost Estimating by Analogy
11.6 Cost Analysis for Composite Manufacturing Processes
11.6.1 Hand Lay-up Technique for Aerospace Parts
11.6.2 Filament Winding for Consumer Goods
11.6.3 Compression Molded SMC Parts for Automotive
Applications
11.7 Learning Curve
11.8 Guidelines for Minimization of Production Cost
References
Bibliography
Questions

Recycling of Composites

12.1 Introduction
12.2 Categories of Dealing with Wastes
12.2.1 Landfilling or Burying
12.2.2 Incineration or Burning
12.2.3 Recycling
12.3 Recycling Methods
12.3.1 Regrinding
12.3.2 Pyrolysis
12.4 Existing Infrastructure for Recycling
12.4.1 Automotive Recycling Infrastructure
12.4.2 Aerospace Recycling Infrastructure
References
Questions

Introduction

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,000 materials available to engineers for the design
products for various applications. These materials
aterials (e.g., copper, cast iron, brass), which have
ral hundred years, to the more recently developed,
.g., composites, ceramics, and high-performance
choice of materials, today’s engineers are posed with
ight selection of a material and the right selection of
s for an application. It is difficult to study all of these
therefore, a broad classification is necessary for sim-
rization.
nding on their major characteristics (e.g., stiffness,
elting temperature), can be broadly divided into four
tals, (2) plastics, (3) ceramics, and (4) composites.
ge number of materials with a range of properties
sults in an overlap of properties with other classes.
mon ceramic materials such as silicon carbide (SiC)
ve densities in the range 3.2 to 3.5 g/cc and overlap
common metals such as iron (7.8 g/cc), copper
m (2.7 g/cc). Table 1.1 depicts the properties of some
h class in terms of density (specific weight), stiffness,
continuous use temperature. The maximum oper-
etals does not degrade the material the way it
d composites. Metals generally tend to temper and
s, thus altering the microstructure of the metals. Due
l changes, modulus and strength values generally
mperature cited in Table 1.1 is the temperature at
ns its strength and stiffness values to at least 90% of
n in the table.

1.1.1 Metals

Metals have been the d
cations. They provide th
neers. The common me
lead, nickel, and titaniu
quently used than pure
rials, sometimes inclu
properties than pure m
corrode, but the additio
and the addition of ch
principle of alloying, th
Metals are, in general,
aluminum, magnesium
Steel is 4 to 7 times heav
heavier than plastics. M
to obtain the final prod

TABLE 1.1

Typical Properties of Some

Material

Metals
Cast iron, grade 20
Steel, AISI 1045 hot rolled
Aluminum 2024-T4
Aluminum 6061-T6
Plastics
Nylon 6/6
Polypropylene
Epoxy
Phenolic
Ceramics
Alumina
MgO
Short fiber composites
Glass-filled epoxy (35%)
Glass-filled polyester (35%)
Glass-filled nylon (35%)
Glass-filled nylon (60%)
Unidirectional composites
S-glass/epoxy (45%)
Carbon/epoxy (61%)
Kevlar/epoxy (53%)
ominating materials in the past for structural appli-
e largest design and processing history to the engi-
tals are iron, aluminum, copper, magnesium, zinc,
m. In structural applications, alloys are more fre-
metals. Alloys are formed by mixing different mate-
ding nonmetallic elements. Alloys offer better
etals. For example, cast iron is brittle and easy to
n of less than 1% carbon in iron makes it tougher,
romium makes it corrosion-resistant. Through the
ousands of new metals are created.
heavy as compared to plastics and composites. Only
, and beryllium provide densities close to plastics.
ier than plastic materials; aluminum is 1.2 to 2 times
etals generally require several machining operations
Engineering Materials
Density
(�)
(g/cc)
Tensile
Modulus
(E)
(GPa)
Tensile
Strength
(�)
(GPa)
Specific
Modulus
(E/�)
Specific
Strength
(�/�)
Max.
Service
Temp.
(°C)
7.0
7.8
2.7
2.7
1.15
0.9
1.25
1.35
3.8
3.6
1.90
2.00
1.62
1.95
1.81
1.59
1.35
100
205
73
69
2.9
1.4
3.5
3.0
350
205
25
15.7
14.5
21.8
39.5
142
63.6
0.14
0.57
0.45
0.27
0.082
0.033
0.069
0.006
0.17
0.06
0.30
0.13
0.20
0.29
0.87
1.73
1.1
14.3
26.3
27.0
25.5
2.52
1.55
2.8
2.22
92.1
56.9
8.26
7.25
8.95
11.18
21.8
89.3
47.1
0.02
0.073
0.17
0.10
0.071
0.037
0.055
0.004
0.045
0.017
0.16
0.065
0.12
0.149
0.48
1.08
0.81
230–300
500–650
150–250
150–250
75–100
50–80
80–215
70–120
1425–1540
900–1000
80–200
80–125
75–110
75–110
80–215
80–215
80–215
uct.

Metals have high sti
electrical conductivity. D
tics, they can be used
requirements.

1.1.2 Plastics

Plastics have become th
decade. In the past 5 ye
exceeded steel producti
corrosion resistance, pla
components, and consu
sheets, rods, bars, powd
facturing process, plast
parts. They can provide
machining operations.
parts.
Plastics are not used
poor thermal stability.
I
less than 100°C. Some p
100 to 200°C without a s
lower melting temperatu

1.1.3 Ceramics

Ceramics have strong c
stability and high hard
major distinguishing ch
they possess almost no
the highest melting poin
for high-temperature an
forms of chemical attac
lurgical techniques and
Due to their high hardn
require net-shape formi
tools, such as carbide a

1.1.4 Composites

Composite materials ha
long time but only in the
of industries with the int
composite materials ha
designed and manufact
ffness, strength, thermal stability, and thermal and
ue to their higher temperature resistance than plas-
for applications with higher service temperature
e most common engineering materials over the past
ars, the production of plastics on a volume basis has
on. Due to their light weight, easy processability, and
stics are widely used for automobile parts, aerospace
mer goods. Plastics can be purchased in the form of
ers, pellets, and granules. With the help of a manu-
ics can be formed into near-net-shape or net-shape
high surface finish and therefore eliminate several
This feature provides the production of low-cost
for high-temperature applications because of their
n general, the operating temperature for plastics is
lastics can take service temperature in the range of
ignificant decrease in the performance. Plastics have
res than metals and therefore they are easy to process.
ovalent bonds and therefore provide great thermal
ness. They are the most rigid of all materials. The
aracteristic of ceramics as compared to metals is that
ductility. They fail in brittle fashion. Ceramics have
ts of engineering materials. They are generally used
d high-wear applications and are resistant to most
k. Ceramics cannot be processed by common metal-
require high-temperature equipment for fabrication.
ess, ceramics are difficult to machine and therefore
ng to final shape. Ceramics require expensive cutting
nd diamond tools.
ve been utilized to solve technological problems for a
1960s did these materials start capturing the attention
roduction of polymeric-based composites. Since then,
ve become common engineering materials and are
ured for various applications including automotive

components, sporting g
marine and oil industri
because of increased
increased competition
Among all materials,
widely used steel and a
Replacing steel compon
in component weight, a
Today, it appears that co
neering applications.

1.2 What Are Com

A composite material is
a unique combination
and can include metal
Fiber-reinforced compo
the constituent material
ically separable. In bulk
remain in their original
are better than constitu
The concept of compo
nature. An example is wo
of natural glue called l
oysters, is an example of
man-made advanced co
from a spider’s web are
other countries, husks or
for several hundred yea
a particulate composite
fiber composite. These r
The main concept of
Typically, composite ma
as shown in Figure 1.1
whiskers, and the matr
The reinforcements ca
fibers can be continuou
matrix have become m
tries. This book focuses
are polymer-based resin
The reinforcing fiber
posite, whereas the mat
forcing fibers are found
oods, aerospace parts, consumer goods, and in the
es. The growth in composite usage also came about
awareness regarding product performance and
in the global market for lightweight components.
composite materials have the potential to replace
luminum, and many times with better performance.
ents with composite components can save 60 to 80%
nd 20 to 50% weight by replacing aluminum parts.
mposites are the materials of choice for many engi-
posites?
made by combining two or more materials to give
of properties. The above definition is more general
s alloys, plastic co-polymers, minerals, and wood.
site materials differ from the above materials in that
s are different at the molecular level and are mechan-
form, the constituent materials work together but
forms. The final properties of composite materials
ent material properties.
sites was not invented by human beings; it is found in
od, which is a composite of cellulose fibers in a matrix
ignin. The shell of invertebrates, such as snails and
a composite. Such shells are stronger and tougher than
mposites. Scientists have found that the fibers taken
stronger than synthetic fibers. In India, Greece, and
straws mixed with clay have been used to build houses
rs. Mixing husk or sawdust in a clay is an example of
and mixing straws in a clay is an example of a short-
einforcements are done to improve performance.
a composite is that it contains matrix materials.
terial is formed by reinforcing fibers in a matrix resin
. The reinforcements can be fibers, particulates, or
ix materials can be metals, plastics, or ceramics.
n be made from polymers, ceramics, and metals. The
s, long, or short. Composites made with a polymer
ore common and are widely used in various indus-
on composite materials in which the matrix materials
s. They can be thermoset or thermoplastic resins.
or fabric provides strength and stiffness to the com-
rix gives rigidity and environmental resistance. Rein-
in different forms, from long continuous fibers to

woven fabric to short ch
different properties. Th
are laid in the composi
can be used in a compo
posites is that the fiber
axis of the fiber. Long c
a composite with prope
material chopped into s
fibers, as illustrated in
(structural or nonstruct
selected. For structural
recommended; whereas
ommended. Injection an
filament winding, pultr

1.3 Functions of F

A composite material
develop a good unders
good knowledge of the
The important function

FIGURE 1.1

Formation of a composite ma

FIGURE 1.2

Continuous fiber and short fi
Fiber
Co
opped fibers and mat. Each configuration results in
e properties strongly depend on the way the fibers
tes. All of the above combinations or only one form
site. The important thing to remember about com-
carries the load and its strength is greatest along the
ontinuous fibers in the direction of the load result in
rties far exceeding the matrix resin itself. The same
hort lengths yields lower properties than continuous
Figure 1.2. Depending on the type of application
ural) and manufacturing method, the fiber form is
applications, continuous fibers or long fibers are
for nonstructural applications, short fibers are rec-
d compression molding utilize short fibers, whereas
usion, and roll wrapping use continuous fibers.
ibers and Matrix
is formed by reinforcing plastics with fibers. To
tanding of composite behavior, one should have a
terial using fibers and resin.
ber composites.
+ =
Resin Composites
ntinuous fiber composites Short fiber composites
roles of fibers and matrix materials in a composite.
s of fibers and matrix materials are discussed below.

The main functions o
• To carry the load
is carried by fibe
• To provide stiffne
properties in the
• To provide electr
type of fiber use
A matrix material ful
of which are vital to the
and of themselves are o
or binder. The importan
• The matrix mater
to the fibers. It p
• The matrix isolat
arately. This stop
• The matrix prov
production of ne
• The matrix provi
ical attack and m
• Depending on th
teristics such as d
A ductile matrix
higher toughnes
are selected.
• The failure mode
used in the comp

1.4 Special Feature

Composites have been r
in which high performa
advantages over traditio
1. Composite mater
eral metallic com
component.
2. Composite struct
cess monitoring
is used to monit
f the fibers in a composite are:
. In a structural
composite, 70 to 90% of the load
rs.
ss, strength, thermal stability, and other structural
composites.
ical conductivity or insulation, depending on the
d.
fills several functions in a composite structure, most
satisfactory performance of the structure. Fibers in
f little use without the presence of a matrix material
t functions of a matrix material include the following:
ial binds the fibers together and transfers the load
rovides rigidity and shape to the structure.
es the fibers so that individual fibers can act sep-
s or slows the propagation of a crack.
ides a good surface finish quality and aids in the
t-shape or near-net-shape parts.
des protection to reinforcing fibers against chem-
echanical damage (wear).
e matrix material selected, performance charac-
uctility, impact strength, etc. are also influenced.
will increase the toughness of the structure. For
s requirements, thermoplastic-based composites
is strongly affected by the type of matrix material
osite as well as its compatibility with the fiber.
s of Composites
outinely designed and manufactured for applications
nce and light weight are needed. They offer several
nal engineering materials as discussed below.
ials provide capabilities for part integration. Sev-
ponents can be replaced by a single composite
ures provide in-service monitoring or online pro-
with the help of embedded sensors. This feature
or fatigue damage in aircraft structures or can be

utilized to monit
ing) process. M
“smart” material
3. Composite mater
sity ratio), as sho
steel at one fifth
one half the weig
4. The specific stre
material is very h
faster and with b
cally in the range
Due to this high
are lighter than t
5. The fatigue stren
ite materials. St
strength up to a
carbon/epoxy co
90% of their stat
6. Composite mater
minum corrode i
coatings and allo
formed by plastic
7. Composite mate
For example, the
posite structures
and lay-up sequ
lower than for m
sional stability.
8. Net-shape or nea
materials. This f
and thus reduces
9. Complex parts, a
times not possib
materials withou
increases reliabil
manufacturing fe
10. Composite mater
for manufacturin
niques. These tec
product and thus
joints, high-stren
cost. Cost benefi
DFM and DFA te
or the resin flow in an RTM (resin transfer mold-
aterials with embedded sensors are known as
s.
ials have a high specific stiffness (stiffness-to-den-
wn in Table 1.1. Composites offer the stiffness of
the weight and equal the stiffness of aluminum at
ht.
ngth (strength-to-density ratio) of a composite
igh. Due to this, airplanes and automobiles move
etter fuel efficiency. The specific strength is typi-
of 3 to 5 times that of steel and aluminum alloys.
er specific stiffness and strength, composite parts
heir counterparts.
gth (endurance limit) is much higher for compos-
eel and aluminum alloys exhibit good fatigue
bout 50% of their static strength. Unidirectional
mposites have good fatigue strength up to almost
ic strength.
ials offer high corrosion resistance. Iron and alu-
n the presence of water and air and require special
ying. Because the outer surface of composites is
s, corrosion and chemical resistance are very good.
rials offer increased amounts of design flexibility.
coefficient of thermal expansion (CTE) of com-
can be made zero by selecting suitable materials
ence. Because the CTE for composites is much
etals, composite structures provide good dimen-
r-net-shape parts can be produced with composite
eature eliminates several machining operations
process cycle time and cost.
ppearance, and special contours, which are some-
le with metals, can be fabricated using composite
t welding or riveting the separate pieces. This
ity and reduces production times. It offers greater
asibility.
ials offer greater feasibility for employing design
g (DFM) and design for assembly (DFA) tech-
hniques help minimize the number of parts in a
reduce assembly and joining time. By eliminating
gth structural parts can be manufactured at lower
t comes by reducing the assembly time and cost.
chniques are discussed in Chapter 5.

11. Composites offer
and 1.4. Figure 1
glass/epoxy, kev
composites. Glas
strength than stee
erties of short an
aluminum and
impact propert
(NylonLG60) wit
posite (NylonSG4
pylene composite
polypropylene co
glass fiber PPS c
long glass fiber p
content are descr
improved impact
12. Noise, vibration,
for composite ma

FIGURE 1.3

Impact properties of various
about 60% fiber volume fract

Im
pa
ct
E
ne
rg
y
Ch
ar
py
, K
J/
m
2
0
100
200
300
400
500
600
700
800
60
61
-T
6
Al
good impact properties, as shown in Figures 1.3
.3 shows impact properties of aluminum, steel,
lar/epoxy, and carbon/epoxy continuous fiber
s and Kevlar composites provide higher impact
l and aluminum. Figure 1.4 compares impact prop-
d long glass fiber thermoplastic composites with
magnesium. Among thermoplastic composites,
ies of long glass fiber nylon 66 composite
h 60% fiber content, short glass fiber nylon 66 com-
0) with 40% fiber content, long glass fiber polypro-
(PPLG40) with 40% fiber content, short glass fiber
mposite (PPSG40) with 40% fiber content, long
omposite (PPSLG50) with 50% fiber content, and
olyurethane composite (PULG60) with 60% fiber
ibed. Long glass fiber provides three to four times
properties than short glass fiber composites.
engineering materials. Unidirectional composite materials with
ion are used. (Source: Data adapted from Mallick.1)
Material
T-
30
0
70
75
-T
6
Al
43
40
S
te
el
S
G
la
ss
/e
po
xy
K
ev
la
r 4
9/
ep
ox
y
B
o
ro
n
/e
po
xy
A
S
Ca
rb
on
/e
po
xy
H
M
S
ca
rb
on
/e
po
xy
c
a
rb
on
/e
po
xy
and harshness (NVH) characteristics are better
terials than metals. Composite materials dampen

vibrations an ord
acteristics are us
edge of an airpla
13. By utilizing prope
tive composite pa
freedom by tailor
fications, thus avo
by changing the fi
14. Glass-reinforced
FAA and JAR req
is required for ai
15. The cost of tool
lower than that
and temperature
design changes i
is continuously r

1.5 Drawbacks of

Although composite m
following disadvantage

FIGURE 1.4

Impact properties of long gla
posites. Fiber weight percent
0
2
4
6
8
10
12
14
16
N
ot
ch
ed
Iz
od
(f
t-l
b/i
n)
A
l
er of magnitude better than metals. These char-
ed in a variety of applications, from the leading
ne to golf clubs.
r design and manufacturing techniques, cost-effec-
rts can be manufactured. Composites offer design
ing material properties to meet performance speci-
iding the over-design of products. This is achieved
ber orientation, fiber type, and/or resin systems.
and aramid-reinforced phenolic composites meet
uirements for low smoke and toxicity. This feature
rcraft interior panels, stowbins, and galley walls.
ing required for composites processing is much
for metals processing because of lower pressure
requirements. This offers greater flexibility for
n this competitive market where product lifetime
educing.
Composites
ss (LG) and short glass (SG) fibers reinforced thermoplastic com-
is written at the end in two digits.
Material
M
g
Ny
lo
nL
G
60
Ny
lo
nS
G
40
PP
LG
40
PP
SG
40
PP
SL
G5
0
PU
LG
60
aterials offer many benefits, they suffer from the
s:

1. The materials co
to that of steel an
aluminum and s
costs $1.00 to $8.
$1.50/lb; glass/e
prepreg costs $1
and that of alum
2. In the past, comp
of large structure
lack of high-volu
of composite mat
(RTM), structura
molding of sheet
have been autom
require the produ
Corvette volume
is 2000 vehicles p
Saginaw Steering
ing systems per d
as golf shafts are
3. Classical ways of
of machinery and
Large design data
composites lacks
4. The temperature
perature resistan
tion of composi
resistance is limit
work in the temp
ture limit can ran
plastics such as e
the maximum co
5. Solvent resistanc
cracking of com
Some polymers h
stress cracking.
6. Composites abso
dimensional stab

1.6 Composites Pr

Processing is the scienc
other. Because composi
st for composite materials is very high compared
d aluminum. It is almost 5 to 20 times more than
teel on a weight basis. For example, glass fiber
00/lb; carbon fiber costs $8 to $40/lb; epoxy costs
poxy prepreg costs $12/lb; and carbon/epoxy
2 to $60/lb. The cost of steel is $0.20 to $1.00/lb
inum is $0.60 to $1.00/lb.
osite materials have been used for the fabrication
s at low volume (one to three parts per day). The
me production methods limits the widespread use
erials. Recently, pultrusion, resin transfer molding
l reaction injection molding (SRIM), compression
molding compound (SMC), and filament winding
ated for higher production rates. Automotive parts
ction of 100 to 20,000 parts per day. For example,
is 100 vehicles per day, and Ford-Taurus volume
er day. Steering system companies such as Delphi
Systems and TRW produce more than 20,000 steer-
ay for various models. Sporting good items such
produced on the order of 10,000 pieces per day.
designing products with metals depend on the use
metals handbooks, and design and data handbooks.
bases are available for metals. Designing parts with
such books because of the lack of a database.
resistance of composite parts depends on the tem-
ce of the matrix materials. Because a large propor-
tes uses polymer-based matrices, temperature
ed by the plastics’ properties. Average composites
erature range –40 to +100°C. The upper tempera-
ge between +150 and +200°C for high-temperature
poxies, bismaleimides, and PEEK. Table 1.2 shows
ntinuous-use temperature for various polymers.
e, chemical resistance, and environmental stress
posites depend on the properties of polymers.
ave low resistance to solvents and environmental
rb moisture, which affects the properties and
ility of the composites.
ocessing
e of transforming materials from one shape to the
te materials involve two or more different materials,

the processing techniqu
for metals processing. T
niques available to pro
systems. It is the job of
cessing technique and p
duction rate, and cost
make informed judgmen
plish the most for the le
knowledge of the benefi
the various manufactur
thermoset and thermopl
fabrication steps, limitat
Figure 1.5 classifies the
the composites industry

1.7 Composites Pr

Composite products ar
final shape using one of

TABLE

Maxim

for Va

Materi

Therm
Viny
Poly
Phen
Epox
Cyan
Bism
Therm
Poly
Poly
Acet
Nylo
Poly
PPS
PEE
Teflo
es used with composites are quite different than those
here are various types of composites processing tech-
cess the various types of reinforcements and resin
a manufacturing engineer to select the correct pro-
rocessing conditions to meet the performance, pro-
requirements of an application. The engineer must
ts regarding the selection of a process that can accom-
ast resources. For this, engineers should have a good
ts and limitations of each process. This book discusses
ing processes frequently used in the fabrication of
astic composites, as well as the processing conditions,
ions, and advantages of each manufacturing method.
frequently used composites processing techniques in
. These methods are discussed in Chapter 6.
oduct Fabrication
1.2
um Continuous-Use Temperatures
rious Thermosets and Thermoplastics
als
Maximum
Continuous-Use
Temperature
(°C)
osets
lester
ester
olics
y
ate esters
aleimide
oplastics
ethylene
propylene
al
n
ester
K
n
60–150
60–150
70–150
80–215
150–250
230–320
50–80
50–75
70–95
75–100
70–120
120–220
120–250
200–260
e fabricated by transforming the raw material into
the manufacturing process discussed in Section 1.6.

The products thus fabri
bers as required for th
divided into the follow
1.

Forming.

In this
and size, usually
composites proc
this category. Com
in Chapter 6.
2.

Machining.

Mac
undesired mater
in this category. C
tools and operat
machining of com
3.

Joining and asse

different compon
task. Adhesive bo
are commonly u
tions are time co
should be avoid
This is achieved
Chapter 5. Joinin
product formatio

FIGURE 1.5

Classification of composites p
Thermoset comp
processing
Short fiber
composites
- SMC molding
- SRIM
- BMC molding
- Spray-up
- Injection
molding
-
-
-
-
-
-
-
-
C
cated are machined and then joined with other mem-
e application. The complete product fabrication is
ing four steps:
step, feedstock is changed into the desired shape
under the action of pressure and heat. All the
essing techniques described in Section 1.6 are in
posite-forming operations are discussed in detail
hining operations are used to remove extra or
ial. Drilling, turning, cutting, and grinding come
omposites machining operations require different
ing conditions than that required by metals. The
posites is discussed in Chapter 10.
mbly. Joining and assembly is performed to attach
ents in a manner so that it can perform a desired
nding, fusion bonding, mechanical fastening, etc.
sed for assmbling two components. These opera-
nsuming and cost money. Joining and assembly
ed as much as possible to reduce product costs.
by part integration as discussed in detail in
rocessing techniques.
formin
Composites processing
osites

Thermoplastic composites
processing
composites
Short fiber
composites
Continuous fiber
composites
Filament winding
Pultrusion
RTM
Hand lay-up
Autoclave process
Roll wrapping
SCRIMP
Bladder molding
- Injection
molding
- Blow molding
- Thermoforming
- Tape winding
- Compression
molding
- Autoclave
- Diaphragm
g
ontinuous fiber
g and assembly operations used for composite
ns are discussed in Chapter 9.

Finishing.

Finish
such as to impr
against environm
coating, and/or
a metal. Golf sha
composite shafts
It is not necessary th
manufacturing compan
to another company fo
driveshaft made in a fila
or tier 2) for assembly w
(original equipment ma
clubs, tennis rackets, fi
and then sent directly t

1.8 Composites M

There are many reason
primary impetus is that
and lighter. Today, it is d
benefits of composite
today is the transportat
composites in 2000. Com
for several industries.
In the past three to fo
technology and its requ
new needs and opportu
new materials and their
In the past decade, sev
rial systems have been
market segments. Sever
posite materials. The v
to the decrease in the co
techniques and high-vo
carbon fiber decreased
This decrease in cost w
methods and increased
Broadly speaking, the
industry categories: aer
resistant equipment, co
and others. U.S. compo
Figure 1.6 for the years
ing operations are performed for several reasons,
ove outside appearance, to protect the product
ental degradation, to provide a wear-resistant
to provide a metal coating that resembles that of
ft companies apply coating and paints on outer
to improve appearance
and look.
at all of the above operations be performed at one
y. Sometimes a product made in one company is sent
r further operations. For example, an automotive
ment winding company is sent to automakers (tier 1
ith their final product, which is then sold to OEMs
nufacturers). In some cases, products such as golf
shing rods, etc. are manufactured in one company
o the distributor for consumer use.
arkets
s for the growth in composite applications, but the
the products fabricated by composites are stronger
ifficult to find any industry that does not utilize the
materials. The largest user of composite materials
ion industry, having consumed 1.3 billion pounds of
posite materials have become the materials of choice
ur decades, there have been substantial changes in
irement. This changing environment created many
nities, which are only possible with the advances in
associated manufacturing technology.
eral advanced manufacturing technology and mate-
developed to meet the requirements of the various
al industries have capitalized on the benefits of com-
ast expansion of composite usage can be attributed
st of fibers, as well as the development of automation
lume production methods. For example, the price of
from $150.00/lb in 1970 to about $8.00/lb in 2000.
as due to the development of low-cost production
industrial use.
composites market can be divided into the following
ospace, automotive, construction, marine, corrosion-
nsumer products, appliance/business equipment,
site shipments in the above markets are shown in
1999 and 2000 (projected).

1.8.1 The Aerospace

The aerospace industry
posite materials. Airpla
farther with the help of
ites have been routinel
The aerospace industry
their high-performance
mon manufacturing me
filament winding are al
In 1999, the aerospace
as shown in Figure 1.6. M
use composite materials
components used in the
vertical stabilizers, wing
components as shown i
above components are i
planes increases the pay
Figure 1.7 shows the
craft and Figure 1.8 sho
aircraft. Composite com
shown in Figures 1.9 an

FIGURE 1.6

Composite shipments in vari

adapted from the Composite

Sh
ip
m
en
t (
mi
llio
n l
b)
0
200
400
600
800
1,000
1,200
1,400
Ae
ro
sp
ac
e/D
efe
ns
e
Ap
pli
an
ce
/Eq
uip
me
n
Co
Industry
was among the first to realize the benefits of com-
nes, rockets, and missiles all fly higher, faster, and
composites. Glass, carbon, and Kevlar fiber compos-
y designed and manufactured for aerospace parts.
primarily uses carbon fiber composites because of
characteristics. The hand lay-up technique is a com-
thod for the fabrication of aerospace parts; RTM and
so being used.
industry consumed 23 million pounds of composites,
ilitary aircrafts, such as the F-11, F-14, F-15, and F-16,
to lower the weight of the structure. The composite
above-mentioned fighter planes are horizontal and
skins, fin boxes, flaps, and various other structural
n Table 1.3. Typical mass reductions achieved for the
n the range of 20 to 35%. The mass saving in fighter
load capacity as well as the missile range.
typical composite structures used in commercial air-
ws the typical composite structures used in military
ous industries in 1999 and those projected for 2000. (Source: Data
s Fabricators Association.2)
U.S. Composites Market Breakdown
1999
2000E
Industry Type
t
ns
tru
cti
on
Co
ns
um
er
Co
rro
sio
n
Ele
ctr
ica
l/E
lec
tro
nic
Ma
rin
e
Tra
ns
po
rta
tio
n
Ot
he
r
ponents used in engine and satellite applications are
d 1.10, respectively.

The major reasons fo
cations include weight s
orbit (LEO), where temp
tant to maintain dimen
reflecting members. Ca
give a zero coefficient
tubular truss structures
tors, etc. In space shut
2688 lb per vehicle.

TABLE 1.3

Composite Components

F-14
F-15
F-16
B-1
AV-8B
Boeing 737
Boeing 757
Boeing 767
Doors, horizo
Fins, rudders
Vertical and h
Doors, vertic
Doors, rudde
Spoilers, hori
Doors, rudde
Doors, rudde

FIGURE 1.7

Typical composite structures
Inc.)
r the use of composite materials in spacecraft appli-
avings as well as dimensional stability. In low Earth
erature variation is from –100 to +100°C, it is impor-
sional stability in support structures as well as in
rbon epoxy composite laminates can be designed to
of thermal expansion. Typical space structures are
, facesheets for the payload baydoor, antenna reflec-
in Aircraft Applications
Composite Components
ntal tails, fairings, stabilizer skins
, vertical tails, horizontal tails, speed brakes, stabilizer skins
orizontal tails, fin leading edge, skins on vertical fin box
al and horizontal tails, flaps, slats, inlets
rs, vertical and horizontal tails, ailerons, flaps, fin box, fairings
zontal stabilizers, wings
rs, elevators, ailerons, spoilers, flaps, fairings
rs, elevators, ailerons, spoilers, fairings
used in commercial aircraft. (Courtesy of Composites Horizon,
tle composite materials provide weight savings of

FIGURE 1.8

Typical composite structures

FIGURE 1.9

Composite components used
used in military aircraft. (Courtesy of Composites Horizon, Inc.)
in engine applications. (Courtesy of Composites Horizon, Inc.)

Passenger aircrafts su
lower the weight, increa
components made out o

1.8.2 The Automotive

Composite materials ha
applications of the auto
finish, styling details, an
automotive requiremen
composites. Today, com
all categories — from ex
and heavy truck applic
million pounds of comp
Because the automot
posites are not yet acce
composites utilize glass
breakdown of automoti
and manufacturing met

FIGURE 1.10

Composite components used
ch as the Boeing 747 and 767 use composite parts to
se the payload, and increase the fuel efficiency. The
f composites for such aircrafts are shown in Table 1.3.
Industry
ve been considered the “material of choice” in some
motive industry by delivering high-quality surface
d processing options. Manufacturers are able to meet
ts of cost, appearance, and performance utilizing
posite body panels have a successful track record in
otic sports cars to passenger cars to small, medium,
ations. In 2000, the automotive industry used 318
osites.
ive market is very cost-sensitive, carbon fiber com-
pted due to their higher material costs. Automotive
fibers as main reinforcements. Table 1.4 provides a
ve composite usage by applications, matrix materials,
hods.
in satellite applications. (Courtesy of Composites Horizon, Inc.)

1.8.3 The Sporting G

Sports and recreation
composite materials. T
greatest in high-perform
has visited a sporting go
rackets, snow skis, fish
products are light in w
the user in easy handlin
Total 1999 U.S. sport
basketball, baseball, tenn
by the Sporting Goods M
The market for recreatio
RVs, snowmobiles, and
from 1998 sales of $15.39
for 1999, including bal
attributed to golf clubs
million, snowboards to
wholesale values in 199
amount of composites u
ica, 6 million hockey st
capturing 1 to 3% of this

Association, San Franc
worldwide in kites, wh
tubes or pultruded tube
sent half a million of the
of-the-line bicycles, whi

1.8.4 Marine Applica

Composite materials ar
passenger ferries, power

TABLE 1.4

Average Use of Composites

Applications
Usage
(kg

¥¥
¥¥

)

Bumper beam
Seat/load floor
Hood
Radiator
support
Roof panel
Other
Total
42
14
13
4
4
11
89

Source:

The Automotive Comp

oods Industry
equipment suppliers are becoming major users of
he growth in structural composite usage has been
ance sporting goods and racing boats. Anyone who
ods store can see products such as golf shafts, tennis
ing rods, etc. made of composite materials. These
eight and provide higher performance, which helps
g and increased comfort.
s equipment shipment cost (including golf, hockey,
is, etc.) was estimated to be $17.33 billion, as reported
anufacturers Association (North Palm Beach, Florida).
nal transport (bicycles, motorcycles, pleasure boats,
water scooters) was estimated at $17.37 billion, up
billion. The total shipment for golf was $2.66 billion
ls, clubs, and others, with a third of that amount
. The ice skates and hockey are estimated to $225
$183 million, and snow skiing to about $303 million
9. There are no statistics available that describe the
sage in the above sporting segments. In North Amer-
icks are manufactured every year, with composites
market (shafts retail for $60 to $150).4 The Kite Trade
isco, estimated a total sale of $215 million in 1990
ich are generally made by roll wrapping composite
s. Composite bicycle frames and components repre-
se parts, or 600,000 lb of material worldwide in top-
ch sell in the range of $3000 to $5000 per unit.4
tions
in Automobiles per Year, 1988–1993
Matrix Material
Usage
(kg ¥¥¥¥ 106)
Manufacturing
Process
Usage
(kg ¥¥¥¥ 106)
Polyester (TS)
Polypropylene
Polycarbonate/PBT
Polyethylene
Epoxy
Other
Total
42
22
10
4
4
7
89
SMC (comp. mold)
GMT (comp. mold)
Injection molding
Ext. blow mold
Filament wound
Other
Total
40
20
13
5
3
8
89
osites Consortium.3
e used in a variety of marine applications such as
boats, buoys, etc. because of their corrosion resistance

and light weight, which
speed, and portability.
forced plastics (GRP) w
70% of all recreational
a 361-page market repo

total annual domestic b
and total composite sh
mated as 620 million lb
Composites are also us
motivation for the use of
handling and installati
mechanical performance
ing, which minimizes th

1.8.5 Consumer Good

Composite materials ar
tions, such as sewing m
printers, etc. The major
made by molding techn
ing, RTM, and SRIM.

1.8.6 Construction an

The construction and ci
composite materials. Co
that the U.S. infrastructu
Some 42% of this nation
according to Federal Hi
ment has budgeted appr
infrastructure rehabilita
carbon-reinforced plast
handling, repair, and l
durability. It also saves a
and thus minimizes the
Composite usage in e
ing. The columns wrapp
show good potential for

1.8.7 Industrial Appli

The use of composite m
Composites are being u
printing industry and i
gets translated into fuel efficiency, higher cruising
The majority of components are made of glass-rein-
ith foam and honeycomb as core materials. About
boats are made of composite materials according to
rt on the marine industry.5 According to this report
oat shipments in the United States was $8.85 billion
ipments in the boating industry worldwide is esti-
s in 2000.
ed in offshore pipelines for oil and gas extractions. The
GRP materials for such applications includes reduced
on costs as well as better corrosion resistance and
. Another benefit comes from the use of adhesive bond-
e need for a hot work permit if welding is employed.
s
e used for a wide variety of consumer good applica-
achines, doors, bathtubs, tables, chairs, computers,
ity of these components are short fiber composites
ology such as compression molding, injection mold-
d Civil Structures
vil structure industries are the second major users of
nstruction engineering experts and engineers agree
re is in bad shape, particularly the highway bridges.
’s bridges need repair and are considered obsolete,
ghway Administration officials. The federal govern-
oximately $78 billion over the next 20 years for major
tion. The driving force for the use of glass- and
ics for bridge applications is reduced installation,
ife-cycle costs as well as improved corrosion and
significant amount of time for repair and installation
blockage of traffic.
arthquake and seismic retrofit activities is also boom-
ed by glass/epoxy, carbon/epoxy, and aramid/epoxy
these applications.
cations
aterials in various industrial applications is growing.
sed in making industrial rollers and shafts for the
ndustrial driveshafts for cooling-tower applications.

Filament winding show
molded, short fiber com
ings, and pistons. Com
provide improved stiffn

1.9 Barriers in Com

The primary barrier to
costs in some cases, as c
effective the material w
front costs, particularly
cost barrier inhibits res
In general, the cost of
lay-up process. Here, r
total cost of a finished
to Asia, Mexico, and Ko
portion of the total pro
The recycling of comp
a high-volume market s
duction is in the millio
lations and environmen
concern and poses a big
discussed in Chapter 12

References

1. Mallick, P.K.,

Fiber R

Marcel Dekker, New
2. Composites Fabrica
3. Automotive Compo
4. McConnel, V.P., Spo

Composites,

January/
5. Market report on “C
Opportunities and T

Questions

1. What are the diff
based on density
2. What are the ben
s good potential for the above applications. Injection-
posites are used in bushings, pump and roller bear-
posites are also used for making robot arms and
ess, damping, and response time.
posite Markets
the use of composite materials is their high initial
ompared to traditional materials. Regardless of how
ill be over its life cycle, industry considers high up-
when the life-cycle cost is relatively uncertain. This
earch into new materials.
processing composites is high, especially in the hand
aw material costs represent a small fraction of the
product. There is already evidence of work moving
rea for the cases where labor costs are a significant
duct costs.
osite materials presents a problem when penetrating
uch as the automotive industry, where volume pro-
ns of parts per year. With the new goverment regu-
tal awareness, the use of composites has become a
challenge for recycling. Recycling of composites is
.
einforced Composites: Materials, Manufacturing and Design,
York, 1993.
tors Association, U.S.A., 2000.
sites Consortium, U.S.A., 1994.
rts applications — composites at play, High Performance
February 1994.
omposites in Marine Industry — 2001: Market Analysis,
rend,” Publisher: E-Composites.com, Total 362 pages.
erent categories of materials? Rank these materials
, specific stiffness, and specific strength.
efits of using composite materials?

3. What is the func
4. What are the pro
posites?
5. What are the fo
composite produ
6. What are the ma
thermoplastic co
tion of a matrix in a composite material?
cessing techniques for short fiber thermoset com-
ur major steps typically taken in the making of
cts?
nufacturing techniques available for continuous
mposites?

Raw Materials

2.1 Introduction

Each manufacturing m
part fabrication. One ma
method, whereas the sa
fabrication method. Fo
molding compounds in
ing or pultrusion proce
ous fibers and wet resi
requires prepreg system
products. Therefore, it i
raw materials available
Figure 2.1 depicts th
niques and their corresp
for composite manufact
thermoset-based and th
plastics are those that o
plastics can be remelted
and thermoplastics hav
of processing, cost, recy
posite systems, there ar

2.2 Reinforcement

Reinforcements are imp
all the necessary stiffne
like structures. The mos
and boron fibers. Typi

m (0.0008 in.). The d

for Part Fabrication
ethod utilizes a specific type of material system for
terial system may be suitable for one manufacturing
me material system may not be suitable for another
r example, the injection molding process utilizes
pellet form, which cannot be used for filament wind-
ss. Filament winding and pultrusion utilize continu-
n systems in most cases. The roll wrapping process
s for making golf club shafts, bicycle tubes, and other
s important to have a good knowledge of the various
for the manufacture of good composite products.
e various types of composite manufacturing tech-
onding material systems. In general, raw materials
uring processes can be divided into two categories:
ermoplastic-based composite materials. Thermoset
nce solidified (cured) cannot be remelted. Thermo-
and reshaped once they have solidified. Thermosets
e their own advantages and disadvantages in terms
clability, storage, and performance. In all these com-
e two major ingredients: reinforcements and resins.
s
ortant constituents of a composite material and give
ss and strength to the composite. These are thin rod-
t common reinforcements are glass, carbon, aramid
cal fiber diameters range from 5 mm (0.0002 in.) to
iameter of a glass fiber is in the range of 5 to 25 mm,

a carbon fiber is 5 to 8

100

m. Because of this
to various shapes. In g
winding operations. Fo
bin and collectively call
is called “tow.” In comp
fibers. The matrix give
fibers.
Fibers for composite m
fibers to discontinuous
inorganic fibers. The mo
tics (FRP) are glass, carb
and glass fibers are the
three major types of glas
of these fibers are given
S-glass is around $8.00
from low to high modu

FIGURE 2.1

Classification of raw material
Thermo
Compos
Fibers and Resins Prepre
- Filament
winding
- Pultrusion
- RTM
- Spray-up
- Hand lay-up
- Hand lay
- Roll
wrappin
- Autoclav
mm, an aramid fiber is 12.5 m m, and a boron fiber is
thin diameter, the fiber is flexible and easily conforms
eneral, fibers are made into strands for weaving or
r delivery purposes, fibers are wound around a bob-
ed a “roving.” An untwisted bundle of carbon fibers
osites, the strength and stiffness are provided by the
s rigidity to the structure and transfers the load to
aterials can come in many forms, from continuous
fibers, long fibers to short fibers, organic fibers to
st widely used fiber materials in fiber-reinforced plas-
on, aramid, and boron. Glass is found in abundance
cheapest among all other types of fibers. There are
s fibers: E-glass, S-glass, and S2-glass. The properties
in Table 2.1. The cost of E-glass is around $1.00/lb,
/lb, and S-2 glass is $5.00/lb. Carbon fibers range
s.
Feedstock for Composites
set
ites
Thermoplastic
Composite
g SMC, BMC,
TMC
Fibers/Resin,
Commingled
Fibers
Thermo-
plastic
Prepreg/Tape
Molding
Compound
-up
g
e
- Compression
molding
Filament
winding
- Tape
winding
-
-
Pultrusion
- Extrusion
- Autoclave
- Hot press
- Tape
winding
- Injection
molding
lus and low to high strength. Cost of carbon fibers

TABLE 2.1

Properties of Fibers and Conventional Bulk

Material
Diameter
(

�

m)
Dens
(

�

(g/cm

elting
Point
(°C)
% Elongation
at Break
Relative
Cost

Fibers
E-glass 7 2.5 1540+ 4.8 Low
S-glass 15 2.5 1540+ 5.7 Moderate
Graphite, high modulus 7.5 1.9 >3500 1.5 High
Graphite, high strength 7.5 1.7 >3500 0.8 High
Boron 130 2.6 2300 — High
Kevlar 29 12 1.4 500(D) 3.5 Moderate
Kevlar 49 12 1.4 500(D) 2.5 Moderate
Bulk materials
Steel 7.8 1480 5–25 <Low
Aluminum alloys 2.7 600 8–16 Low
© 2002 by CRC Press LLC
Materials
ity
)
3)
Tensile
Modulus
(E)
(GPa)
Tensile
Strength
(�)
(GPa)
Specific
Modulus
(E/�)
Specific
Strength
M
4 70 3.45 27 1.35
0 86 4.50 34.5 1.8
400 1.8 200 0.9
240 2.6 140 1.5
400 3.5 155 1.3
5 80 2.8 55.5 1.9
5 130 2.8 89.5 1.9
208 0.34–2.1 27 0.04–0.27
69 0.14–0.62 26 0.05–0.23

fall in a wide range from
$15.00 to $20.00/lb. Som
• Continuous carb
• Discontinuous ch
• Woven fabric
• Multidirectional
properties)
• Stapled
• Woven or knitted
Continuous fibers ar
weaving, and prepregg
in Figure 2.2 and individ
with most thermoset an
used for making injecti
Chopped fibers are mad
other processes, continu
small pieces before the
prepregs as well as for
boating, marine, and sp
processes and used as re
The next section prov
for glass, carbon, and K

FIGURE 2.2

Glass rovings and yarns. Thr
spools are shown at edges. (C
$8.00 to $60.00/lb. Aramid fibers cost approximately
e of the common types of reinforcements include:
on tow, glass roving, aramid yarn
opped fibers
fabric (stitch bonded for three-dimensional
three-dimensional preforms
e used for filament winding, pultrusion, braiding,
ing applications. Glass rovings and yarns are shown
ual rovings in Figure 2.3. Continuous fibers are used
d thermoplastic resin systems. Chopped fibers are
on molding and compression molding compounds.
e by cutting the continuous fibers. In spray-up and
ous fibers are used but are chopped by machine into
application. Woven fabrics are used for making
making laminates for a variety of applications (e.g.,
orting). Preforms are made by braiding and other
inforcements for RTM and other molding operations.
ee spools of glass yarns are shown at the center and four roving
ourtesy of Saint-Gobain Vetrotex America.)
ides a brief description of manufacturing techniques
evlar fibers.

2.2.1 Glass Fiber Man

The properties of fibers
materials used for maki
boric acid, and clay. Silic
By varying the amounts
glass types are produced
in a furnace at 2,500 to
containing hundreds of
molten glass passes thr
quench area where wate
transition temperature. T
around 50 miles per ho
sizing used ranges from
are then pulled into a si
Sizing is applied to t
easy fiber wetting and
and protects fibers fro
sizing formulation dep
used for epoxy would b

2.2.2 Carbon Fiber M

Carbon and graphite fi
precursors. The precurs
the precursors are oxidiz
Later, they go through
these processes, precurs
ness-to-weight and steng
ment and sizing process

FIGURE 2.3

Photograph of individual rov
ufacturing
depend on how the fibers are manufactured. The raw
ng E-glass fibers are silica sand, limestone, fluorspar,
a accounts for more than 50% of the total ingredients.
of raw materials and the processing parameters, other
. The raw materials are mixed thoroughly and melted
3,000°F. The melt flows into one or more bushings
small orifices. The glass filaments are formed as the
ough these orifices and successively goes through a
r and/or air quickly cool the filaments below the glass
he filaments are then pulled over a roller at a speed
ur. The roller coats them with sizing. The amount of
0.25 to 6% of the original fiber weight. All the filaments
ngle strand and wound onto a tube.
he filaments to serve several purposes; it promotes
processing, provides better resin and fiber bonding,
m breakage during handling and processing. The
ends on the type of application; for example, sizing
e different than that used for polyester.
anufacturing
bers are produced using PAN-based or pitch-based
or undergoes a series of operations. In the first step,
ed by exposing them to extremely high temperatures.
carbonization and graphitization processes. During
ors go through chemical changes that yield high stiff-
ings. (Courtesy of GDP-DFC, France.)
th-to-weight properties. The successive surface treat-
improves its resin compatibility and handleability.

PAN refers to polyacr
is obtained by spinnin
fibers are most widely u
fibers tend to be stiffer
on the cost of the raw m
around $1.50 to $2.00/lb
weight reduces to almos
loss, the cost of fibers ba
The fabrication method
intensive. Therefore, hi
fibers. There is a limita
size more than 12K crea
ment winding and brai
Pitch-based carbon fi
fibers but pitch is more d
to handle. Pitch itself co
it to the fiber form are v
expensive than PAN-ba
The cost of carbon fib
as well as on the tow s
with high stiffness and
size, the lower the cost
fiber bundle) costs less

2.2.3 Aramid Fiber M

Aramid fibers provide
reinforcing fibers. They
they provide a negative
of aramid fibers is that
are produced by extrud
tion product of terephth

spinneret. The filamen
drawing operation, aram
dinal direction.

2.3 Matrix Materia

As discussed, composite
Matrix surrounds the fi
and environmental atta
must have a lower mod
ylonitrile, a polymer fiber of textile origin. Pitch fiber
g purified petroleum or coal tar pitch. PAN-based
sed for the fabrication of carbon fibers. Pitch-based
and more brittle. The cost of carbon fiber depends
aterial and process. The PAN-based precursor costs
. During oxidation and carbonization processes, the
t 50% of the original weight. Considering the weight
sed on raw material alone becomes $3.00 to $4.00/lb.
for the production of carbon fibers is slow and capital
gher tow count is produced to lower the cost of the
tion on increasing the tow size. For example, a tow
tes processing and handling difficulties during fila-
ding operations.
bers are produced in the same way as PAN-based
ifficult to spin and the resultant fiber is more difficult
sts pennies a kilogram, but processing and purifying
ery expensive. Generally, pitch-based fibers are more
sed fibers.
ers depends on the strength and stiffness properties
ize (number of filaments in a fiber bundle). Fibers
strength properties cost more. The higher the tow
will be. For example, 12K tow (12,000 filaments per
than 6K tow.
anufacturing
the highest tensile strength-to-weight ratio among
provide good impact strength. Like carbon fibers,
coefficient of thermal expansion. The disadvantage
they are difficult to cut and machine. Aramid fibers
ing an acidic solution (a proprietary polycondensa-
aloyol chloride and p-phenylenediamine) through a
ts are drawn through several orifices. During the
id molecules beome highly oriented in the longitu-
ls
s are made of reinforcing fibers and matrix materials.
bers and thus protects those fibers against chemical
ck. For fibers to carry maximum load, the matrix
ulus and greater elongation than the reinforcement.

Matrix selection is perf
mability, environmenta
ments. The matrix de
composite as well as pr
mum continuous-use te
thermoplastic resins are

2.3.1 Thermoset Resi

Thermoset materials on
curing, they form three
as shown in Figure 2.4.
flexible and cannot be
cross-linkings, the more
rubbers and other elasto
therefore they are flexib
temperatures. This char
in tubular structures, su
in nature and are genera
Thermoset resins provi
because the liquid resin
such as filament windi
thermal and dimensiona
ical, and solvent resista
moset composites are e
bismaleimides, and po
thermoset resins are sh

FIGURE 2.4

Cross-linking of thermoset m

TABLE 2.2

Typical Unfi

Resin
Material
D

Epoxy
Phenolic
Polyester
ormed based on chemical, thermal, electrical, flam-
l, cost, performance, and manufacturing require-
termines the service operating temperature of a
ocessing parameters for part manufacturing. Maxi-
mperatures of the various types of thermoset and
shown in Table 1.2 in Chapter 1.
ns
ce cured cannot be remelted or reformed. During
-dimensional molecular chains, called cross-linking,
Due to these cross-linkings, the molecules are not
remelted and reshaped. The higher the number of
rigid and thermally stable the material will be. In
mers, the densities of cross-links are much less and
le. Thermosets may soften to some extent at elevated
acteristic is sometimes used to create a bend or curve
ch as filament-wound tubes. Thermosets are brittle
lly used with some form of filler and reinforcement.
de easy processability and better fiber impregnation
is used at room temperature for various processes
ng, pultrusion, and RTM. Thermosets offer greater
l stability, better rigidity, and higher electrical, chem-
nce. The most common resin materials used in ther-
poxy, polyester, vinylester, phenolics, cyanate esters,
lyimides. Some of the basic properties of selected
own in Table 2.2.
olecules during curing.
lled Thermosetting Resin Properties
ensity
(g/cm3)
Tensile Modulus
GPa (106 psi)
Tensile Strength
MPa (103 psi)
1.2–1.4
1.2–1.4
2.5–5.0 (0.36–0.72)
2.7–4.1 (0.4–0.6)
50–110 (7.2–16)
35–60 (5–9)
1.1–1.4 1.6–4.1 (0.23–0.6) 35–95 (5.0–13.8)

2.3.1.1 Epoxy

Epoxy is a very versati
erties and processing ca
lent adhesion to a variet
used resin materials an
sporting goods. There a
performance to meet d
with other materials or
performance need. By c
be changed; the cure
requirement can be cha
tack can be varied, the t
can be improved, etc. E
anhydrides, phenols, ca
resin containing several
nol A (DGEBA), which
is a three-membered ri
addition to this starting
viscosity and flexibilizer
linking) reaction takes
diethylenetriamine [DE
links with each other a
three-dimensional netw
can be controlled throu
Each hardener provides
to the final product. Th
time and thus higher p
Epoxy-based compos
temperatures. Epoxies c
and there are epoxies th
ture and high-performa
chemical and corrosion
Epoxies come in liquid
in RTM, filament windin
various reinforcing fiber
epoxies are used in pre
Solid epoxy capsules are
than polyester and vin
markets (e.g., automotiv
Epoxies are generally
ened epoxies have been
erties of a thermoset w
epoxies are made by ad
patented processes.
le resin system, allowing for a broad range of prop-
pabilities. It exhibits low shrinkage as well as excel-
y of substrate materials. Epoxies are the most widely
d are used in many applications, from aerospace to
re varying grades of epoxies with varying levels of
ifferent application needs. They can be formulated
can be mixed with other epoxies to meet a specific
hanging the formulation, properties of epoxies can
rate can be modified, the processing temperature
nged, the cycle time can be changed, the drape and
oughness can be changed, the temperature resistance
poxies are cured by chemical reaction with amines,
rboxylic acids, and alcohols. An epoxy is a liquid
epoxide groups, such as diglycidyl ether of bisphe-
has two epoxide groups. In an epoxide group, there
ng of two carbon atoms and one oxygen atom. In
material, other liquids such as diluents to reduce its
s to increase toughness are mixed. The curing (cross-
place by adding a hardener or curing agent (e.g.,
TA]). During curing, DGEBA molecules form cross-
s shown in Figure 2.4. These cross-links grow in a
ork and finally form a solid epoxy resin. Cure rates
gh proper selection of hardeners and/or catalysts.
different cure characteristics and different properties
e higher the cure rate, the lower the process cycle
roduction volume rates.
ites provide good performance at room and elevated
an operate well up to temperatures of 200 to 250°F,
at can perform
well up to 400°F. For high-tempera-
nce epoxies, the cost increases, but they offer good
resistance.
, solid, and semi-solid forms. Liquid epoxies are used
g, pultrusion, hand lay-up, and other processes with
s such as glass, carbon, aramid, boron, etc. Semi-solid
preg for vacuum bagging and autoclave processes.
used for bonding purposes. Epoxies are more costly
ylesters and are therefore not used in cost-sensitive
e and marine) unless specific performance is needed.
brittle, but to meet various application needs, tough-
developed that combine the excellent thermal prop-
ith the toughness of a thermoplastic. Toughened
ding thermoplastics to the epoxy resin by various

2.3.1.2 Phenolics

Phenolics meet FAA (a
They are used for aircr
other commercial mark
smoke products.
Phenolics are formed
aldehyde, and catalyze
can be used instead o
characteristics are differ
due to the fact that wa
removed during proces
be removed by bumpin
therefore used for appli
products are usually re
colored products, urea f
Other than flame-res
their capabilities in var
• High temperatur
• Electrical proper
• Wear resistance i
• Good chemical r
Phenolics are used fo
as filament winding, R
Phenolics provide easy
and high strength. Beca
are used in exhaust com
tors, and disc brakes.

2.3.1.3 Polyesters

Polyesters are low-cost r
The operating service te
Polyesters are widely us
operations. Polyesters c
Unsaturated polyeste
tional organic acids w
maleic, fumaric, phthal
glycol, propylene glyco
linking process, a react
50 wt% range. The car
molecules and styrene m
nd JAR) requirements for low smoke and toxicity.
aft interiors, stowbins, and galley walls, as well as
ets that require low-cost, flame-resistant, and low-
by the reaction of phenol (carbolic acid) and form-
d by an acid or base. Urea, resorcinol, or melamine
f phenol to obtain different properties. Their cure
ent than other thermosetting resins such as epoxies,
ter is generated during cure reaction. The water is
sing. In the compression molding process, water can
g the press. Phenolics are generally dark in color and
cations in which color does not matter. The phenolic
d, blue, brown, or black in color. To obtain light-
ormaldehyde and melamine formaldehyde are used.
istant parts, phenolic products have demonstrated
ious other applications where:
e resistance is required.
ties are needed.
s important.
esistance and dimensional stability are essential.
r various composite manufacturing processes such
TM, injection molding, and compression molding.
processability, tight tolerances, reduced machining,
use of their high temperature resistance, phenolics
ponents, missile parts, manifold spacers, commuta-
esin systems and offer excellent corrosion resistance.
mperatures for polyesters are lower than for epoxies.
ed for pultrusion, filament winding, SMC, and RTM
an be a thermosetting resin or a thermoplastic resin.
rs are obtained by the reaction of unsaturated difunc-
ith a difunctional alcohol. The acids used include
ic, and terephthalic. The alcohols include ethylene
l, and halogenated glycol. For the curing or cross-
ive monomer such as styrene is added in the 30 to
bon-carbon double bonds in unsaturated polyester
olecules function as the cross-linking site.

With the growing hea
rene is being reduced f
methods, catalysts are u

2.3.1.4 Vinylesters

Vinylesters are widely u
processes. They offer g
for FRP pipes and tank
epoxies and are used in
where cost is critical in
Vinylesters are forme
acid with an epoxide-te
fewer unsaturated sites
therefore, a cured vinyl

2.3.1.5 Cyanate Este

Cyanate esters offer exc
erties, and lower moist
formulated correctly, th
leimide and polyimide
including spacecrafts, a
ics, and microwave pro
Cyanate esters are for
acid that cyclotrimeriz
Cyanate esters are more
esters can be increased b

2.3.1.6 Bismaleimide

BMI and polyimide are
missiles, and circuit boa

in the range of 550 to 6

700°F. These values are
lack of use of BMIs and
They emit volatiles and
proper venting is neces
may cause process-rela
drawbacks of these res
lower than epoxies and
absorption ability.

2.3.1.7 Polyurethane

Polyurethane is widely
processes and reinforce
lth concerns over styrene emissions, the use of sty-
or polyester-based composite productions. In recent
sed for curing polyesters with reduced styrene.
sed for pultrusion, filament winding, SMC, and RTM
ood chemical and corrosion resistance and are used
s in the chemical industry. They are cheaper than
the automotive and other high-volume applications
making material selection.
d by the chemical reaction of an unsaturated organic
rminated molecule. In vinylester molecules, there are
for cross-linking than in polyesters or epoxies and,
ester provides increased ductility and toughness.
rs
ellent strength and toughness, better electrical prop-
ure absorption compared to other resins. If they are
eir high-temperature properties are similar to bisma-
resins. They are used for a variety of applications,
ircrafts, missiles, antennae, radomes, microelectron-
ducts.
med via the reaction of bisphenol esters and cyanic
e to produce triazine rings during a second cure.
easily cured than epoxies. The toughness of cyanate
y adding thermoplastics or spherical rubber particles.
(BMI) and Polyimide
used for high-temperature applications in aircrafts,
rds. The glass transition temperature (Tg) of BMIs is
00°F, whereas some polyimides offer Tg greater than
much higher than for epoxies and polyesters. The
polyimides is attributed to their processing difficulty.
moisture during imidization and curing. Therefore,
sary during the curing of these resins; otherwise, it
ted defects such as voids and delaminations. Other
ins include the fact that their toughness values are
cyanate esters, and they have a higher moisture
used for structural reaction injection molding (SRIM)
d reaction injection molding (RRIM) processes, in

which isocyanate and p
chamber and then rapi
long fiber reinforcemen
volume production me
these processes. Polyure
such as bumper beams
used for various appli
cushions, mattress foam
resistance coatings.
Polyurethane can be a
the functionality of the
contains linear molecu
linked molecules.
Polyurethane is obtai
polyhydroxyl group. Th
ing various types of pol
thane offers excellent w
and high resilience.

2.3.2 Thermoplastic R

Thermoplastic materials
materials and are used f
out fillers and reinforce
solidified by cooling, w
reforming. Thermoplast
flexible and reformable
crystalline, as shown in
are randomly arranged;
plastics, molecules are
have 100% crystallinity
molecules. Some of the
Their lower stiffness an
forcements for structura
creep resistance, especia
sets. They are more sus
resins can be welded tog
than for thermosets. Rep
requiring adhesives and
ites typically require hig
parable thermoset syste
a level of integration a
The higher viscosity of t
cesses, such as hand lay
a consequence of this, t
drawn a lot of attention
olyol are generally mixed in a ratio of 1:1 in a reaction
dly injected into a closed mold containing short or
ts. RRIM and SRIM processes are low-cost and high-
thods. The automotive industry is a big market for
thane is currently used for automotive applications
, hoods, body panels, etc. Unfilled polyurethane is
cations, including truck wheels, seat and furniture
, etc. Polyurethane is also used for wear and impact
thermosetting or thermoplastic resin, depending on
selected polyols. Thermoplastic-based polyurethane
les, whereas thermoset-based resin contains cross-
ned by the reaction
between polyisocyanate and a
ere are a variety of polyurethanes available by select-
yisocyanate and polyhydroxyl ingredients. Polyure-
ear, tear, and chemical resistance, good toughness,
esins
are, in general, ductile and tougher than thermoset
or a wide variety of nonstructural applications with-
ments. Thermoplastics can be melted by heating and
hich render them capable of repeated reshaping and
ic molecules do not cross-link and therefore they are
. Thermoplastics can be either amorphous or semi-
Figure 2.5. In amorphous thermoplastics, molecules
whereas in the crystalline region of semi-crystalline
arranged in an orderly fashion. It is not possible to
in plastics because of the complex nature of the
properties of themoplastics are given in Table 2.3.
d strength values require the use of fillers and rein-
l applications. Thermoplastics generally exhibit poor
lly at elevated temperatures, as compared to thermo-
ceptible to solvents than thermosets. Thermoplastic
ether, making repair and joining of parts more simple
air of thermoset composites is a complicated process,
careful surface preparation. Thermoplastic compos-
her forming temperatures and pressures than com-
ms. Thermoplastic composites do not enjoy as high
s is currently obtained with thermosetting systems.
hermoplastic resins makes some manufacturing pro-
-up and tape winding operations, more difficult. As
he fabrication of thermoplastic composite parts have
from researchers to overcome these problems.

2.3.2.1 Nylons

Nylons are used for m
bushings, sprockets, etc
are available for injectio
for injection molding pu
reinforcements. Nylons
Nylons are also called
ing nylon 6, nylon 66,

FIGURE 2.5

Molecular arrangements in (a

TABLE 2.3

Typical Unfille

Resin
Material

Nylon
PEEK
PPS
Polyester
Polycarbonate
Acetal
Polyethylene
Teflon
(a)
aking intake manifolds, housings, gears, bearings,
. Glass-filled and carbon-filled nylons in pellet form
n molding purposes. Nylons are most widely used
rposes, but are also available as prepregs with various
have been used for various pultruded components.
polyamides. There are several types of nylon, includ-
) amorphous and (b) semi-crystalline polymers.
d Thermoplastic Resin Properties
Density
(g/cm3)
Tensile Modulus
GPa (106 psi)
Tensile Strength
MPa (103 psi)
1.1
1.3–1.35
1.3–1.4
1.3–1.4
1.2
1.4
0.9–1.0
2.1–2.3
1.3–3.5 (0.2–0.5)
3.5–4.4 (0.5–0.6)
3.4 (0.49)
2.1–2.8 (0.3–0.4)
2.1–3.5 (0.3–0.5)
3.5 (0.5)
0.7–1.4 (0.1–0.2)
—
55–90 (8–13)
100 (14.5)
80 (11.6)
55–60 (8–8.7)
55–70 (8–10)
70 (10)
20–35 (2.9–5)
10–35 (1.5–5.0)
(b)
Amorphous
region
Crystalline region
nylon 11, etc., each offering a variety of mechanical

and physical propertie
plastics. Nylons provid
important design consi
which affects the prop
reinforcement minimize
tant material. Impact r
conventional engineerin
shown in Figure 1.4 in

2.3.2.2 Polypropylen

Polypropylene (PP) is a
able in many grades an
lowest density (0.9 g/c

stiffness, chemical resis
parts, car components (
and has also been pultr

2.3.2.3 Polyetherethe

PEEK is a new-generati
high service temperatu
have already demostra
other aerospace structur
transition temperature

perature is ~336°C. PE
matic polymer compo
researchers and in the
tolerance, better solven
PEEK has the advantag
epoxies. The water abso
aerospace-grade epoxie
PEEK-based composite
$50.00/lb.
PEEK/carbon is proc
press, and diaphragm m
tion, more than 500°C i

semi-crystalline materia
the crystallinity of PEE
50 to 100 times higher t

2.3.2.4 Polyphenylen

PPS is an engineering t
It provides high operat
225°C. The T

of PPS
s; but as a whole, they are considered engineering
e a good surface appearance and good lubricity. The
deration with nylons is that they absorb moisture,
erties and dimensional stability of the part. Glass
s this problem and produces a strong, impact-resis-
esistance of long glass-filled nylon is higher than
g materials such as aluminim and magnesium, as
Chapter 1.
e (PP)
low-cost, low-density, versatile plastic and is avail-
d as a co-polymer (ethylene/propylene). It has the
m3) of all thermoplastics and offers good strength,
tance, and fatigue resistance. PP is used for machine
fans, fascia panels, etc.), and other household items,
uded with various reinforcements.
rketone (PEEK)
on thermoplastic that offers the possibility of use at
res. Carbon-reinforced PEEK composites (APC-2)
ted their usefulness in fuselage, satellite parts, and
es; they can be used continuously at 250°C. The glass
(Tg) of PEEK is 143°C and crystalline melting tem-
EK/carbon thermoplastic composites (APC-2, aro-
sites) have generated significant interest among
aircraft industry because of their greater damage
t resistance, and high-temperature usage. As well,
e of almost 10 times lower water absorption than
rption of PEEK is 0.5% at room temperature, whereas
s have 4 to 5% water absorption. The drawback of
s is that the materials cost is very high, more than
essed in the range of 380 to 400°C for autoclave, hot
olding processes whereas for tape winding opera-
s suggested for better interply consolidation.1 It is a
l with a maximum crystallinity of 48%. In general,
K is 30 to 35%. The toughness offered by PEEK is
han that of epoxies.
e Sulfide (PPS)
hermoplastic with a maximum crystallinity of 65%.
ing temperatures and can be used continuously at
is 85°C and crystalline melt temperature is 285°C.

Prepreg tape of PPS with
of PPS-based prepreg sy
temperature range of 30
cations where great stre
temperature.

2.4 Fabrics

There are two major typ
fabrics and nonwoven (

2.4.1 Woven Fabrics

Woven fabrics are used
blades, and in other mar
yarns, rovings, or tows
are shown in Figure 2.6.
styles. The amount of fi
pattern. For example, i
such a way that the fibe
In a plain-weave patter
uted. Hybrid fabrics in

FIGURE 2.6

Various weave styles for fabr
several reinforcements is available. The trade names
stems are Ryton and Techtron. It is processed in the
0 to 345°C. PPS-based composites are used for appli-
ngth and chemical resistance are required at elevated
es of fabrics available in composites industry: woven
noncrimp) fabrics.
in trailers, containers, barge covers, and water tower
ine wet lay-up applications. These fabrics are woven
in mat form in a single layer. Common weave styles
Figure 2.7 shows carbon fabrics in a variety of weave
ber in different directions is controlled by the weave
n unidirectional woven fabrics, fibers are woven in
rs in 0° are up to 95% of the total weight of the fabric.
n, fibers in 0° and 90° directions are equally distrib-
various combinations, such as glass/carbon and
ics. (Courtesy of Cytec Fiberite.)

aramid/carbon, are also
wires are woven into
lightning, thus minimiz
Woven fabrics are also
processes as feedstock. W

2.4.2 Noncrimp Fabr

In noncrimp fabrics, ya
Figure 2.8 and then stitc
tional fabric is used whe
in stiffness-critical appli
is laid along the length
fabrics, reinforcements
Figure 2.9; whereas in w
90° (or weft direction) o
used in filament woun

FIGURE 2.7

Carbon fabrics with a variety

FIGURE 2.8

Schematic of noncrimp fabric
45°
available. For lightning strike purposes, conductive
fabric forms to distribute the energy imparted by
ing damage to the structure.
used to make prepregs, as well as in RTM and SRIM
oven fabrics have the advantage of being inexpensive.
ics
rns are placed parallel
to each other as shown in
hed together using polyester thread. Warp unidirec-
n fibers are needed in one direction only, for example,
cations such as water ski applications where the fabric
of the ski to improve resistance to bending. In warp
are laid at 0° (or warp direction) only as shown in
eft unidirectional fabrics, reinforcements are laid at
of weave styles. (Courtesy of Cytec Fiberite.)
s.
90°
0°
nly as shown in Figure 2.10. Weft fabrics are typically
d tubes and pipes and also pultruded components

where reinforcement
(0°, ±45°) fabric is used
ity, whereas weft triax
stiffness and torsional
viding strength in all f
the weight range of 9 to

compared to woven fab
angle from 0° to 90°, in
to make multiaxial stit
rovings mostly on the

FIGURE 2.9

Warp unidirectional fabrics.

FIGURE 2.10

Weft unidirectional fabrics.
St
Sti
in the weft direction is necessary. Warp triaxial
to increase longitudinal stiffness and torsional rigid-
ial (90°, ±45°) fabric is used to increase transverse
rigidity. Quadraxial fabrics are quasi-isotropic, pro-
our fiber axial directions. Fabrics typically come in
200 oz/yd2. Noncrimp fabrics offer greater flexibility
rics. For example, fibers can be laid at almost any
cluding 45°, 90°, 30°, 60°, and 22°, and then stitched
ched plies, whereas woven fabrics are made from
0° and 90° axes. Noncrimp fabrics offer greater
itched thread Yarns
Yarnstched thread

strength because fibers
bend over each other. N
thus an entire laminate
useful in making thicke
ber of fabrication steps.
To make noncrimp gl
bers in combinations o
yield number denotes a
to achieve a given weig
the physical, mechanic
finer filaments mean h
strength and can reduc
To meet the market n
combinations of plies
which woven fabrics an
the fabric. Figure 2.12 sh
cut fibers 5 to 10 cm in

FIGURE 2.11

Illustration of bi-ply fabric.

FIGURE 2.12

Photograph of a mat. (Courte
Mat
remain straight; whereas in woven fabrics, fibers
oncrimp fabrics are available in a thick layer and
could be achieved in a single-layer fabric. This is
r laminates such as boat hulls and reduces the num-
ass fabrics, input rovings are selected by yield num-
f 113, 218, 450, 675, 1200, and 1800 yd/lb. A larger
finer roving and, therefore, more yards are required
ht. The selection of yield number is determined by
al, and aesthetic requirements of the laminate. The
igher fiber content and less resin. This improves
e weight.
eed for heavier fabrics, stitched fabrics with various
are produced. Figure 2.11 shows a bi-ply fabric in
d a chopped strand mat are stitched together to form
ows a mat made using continuous fibers or random
length.
sy of GDP-DFC, France.)
Woven fabrics

2.5 Prepregs

A prepreg is a resin-im
stored for later use in h
orientation and preimp
Figure 2.13 shows the v
tape, woven fabric tape
directional prepreg tap
the composite propertie
used to make highly co
is also used to make sa
Preimpregnated rovings
Epoxy-based prepreg
form in a thickness ra
Prepregs can be broadly
plastic-based prepregs/
of resin used. Reinforce
and are used in filame
prepreg. Table 2.4 provi
properties of advanced
and thermoplastic-base
plain weave fabric form
wide range of material
vides easy and quick a

FIGURE 2.13

Prepreg types: unidirectiona
Fiberite.)
pregnated fiber, fabric, or mat in flat form, which is
and lay-up or molding operations. Fibers laid at 0°
regnated with resin are called unidirectional tape.
arious types of prepregs available as unidirectional
, and rovings. Figure 2.14 shows the making of uni-
e. Unidirectional tape provides the ability to tailor
s in the desired direction. Woven fabric prepregs are
ntoured parts in which material flexibility is key. It
ndwich panels using honeycomb as a core material.
are primarily used in filament winding applications.
s are very common in industry and come in flat sheet
nge of 0.127 mm (0.005 in.) to 0.254 mm (0.01 in.).
classified as thermoset-based prepregs and thermo-
tapes, the difference between the two being the type
ments in a prepreg can be glass, carbon, or aramid,
nt or woven fabric or mat form in either type of
des an overview of the basic mechanical and physical
composite prepreg systems. Properties of thermoset-
d prepreg tapes with unidirectional fibers, as well as
s, are also shown in the table. The table presents a
l tape, woven fabric prepregs, and rovings. (Courtesy of Cytec
possibilities and performance potentials, which pro-
ssessment of the various prepregs. There are more

than 100 prepreg types
needs.
Prepregs provide con
mix and complete wet-o
resin and catalyst. Var
prepregs to meet variou
to take the shape of a con
are not easy to drape, w
is the stickiness of uncu
for easy laying and proc
tack, they are welded
prepregs have a limited
eration minimizes the d
causes thermoset prepr
Unidirectional prepre
ranging from 0.5 to 60
orientations, the stiffne
properties of the struct
in a number of weave p
Fabric prepregs are mad
a hot melt process or b
of flexibility in highly co
aircraft parts, sandwich

FIGURE 2.14

Making unidirectional prepre
available on the market to meet various application
sistent properties as well as consistent fiber/resin
ut. They eliminate the need for weighing and mixing
ious types of drape and tack are provided with
s application needs. Drape is the ability of prepreg
toured surface. For example, thermoplastic prepregs
hereas thermoset prepregs are easy to drape. Tack
red prepregs. A certain amount of tack is required
essing. Because thermoplastic tapes do not have any
with another layer while laying up. Thermoset
shelf life and require refrigeration for storage. Refrig-
egree of cure in the prepreg materials because heat
egs to cure.
g tapes are available in a wide variety of widths,
in. By laying unidirectional tapes at desired ply
ss, strength, and coefficient of thermal expansion
ure can be controlled. Fabric prepregs are available
atterns in standard widths ranging from 39 to 60 in.
e by preimpregnating woven fabrics with resin via
y solution treatment. They provide a good amount
g tape. (Courtesy of Cytec Fiberite.)
ntoured and complex parts. They are used in making
panels, sporting goods, industrial products, and

TABLE 2.4

Properties of Various Prepreg M

Prepreg Material
F
Vo
Fra Shelf Life
(0°F, Months)
Out Time
at Room
Temp.
(Days )

Unidirectional thermoset
Carbon (AS4, T-300)/epoxy 5 6–12 14–30
Carbon (IM7)/epoxy 5 12 30
S-2 glass/epoxy 5 6 10–30
Kevlar/epoxy 5 6 10–30
Carbon (AS4)/bismaleimide 5 6 25
Carbon (IM7)/bismaleimide 6 6–12 25
Carbon (IM7)/cyanate ester 5 6 10
S-2 glass/cyanate ester 5 6 10
Unidirectional thermoplastic
Carbon (IM7)/PEEK 5 Indefinite Indefinite
Carbon (G34/700)/Nylon 6 5 Indefinite Indefinite
Aramid/Nylon 12 5 Indefinite Indefinite
Carbon (AS4)/PPS 6 Indefinite Indefinite
Carbon (IM7)/polyimide 6 Indefinite Indefinite
Fabric (plain weave) thermoset
Carbon (AS4)/epoxy 5 6 10
S-2 glass/epoxy 5 6 10
Fabric (plain weave)
thermoplastic tape
Carbon HM (T650-35)/
polyimide
5 12 Indefinite
© 2002 by CRC Press LLC
aterials
iber
lume
ction
(%)
Processing
Temp.
(°F)
Tensile
Modulus
(Msi)
Tensile
Strength
(ksi)
Compressive
Modulus
(Msi)
Compressive
Strength
(ksi)
Maximum
Service Temp.
(0°F, Dry)
5–65 250 15–22 180–320 15–20 160–250 180–250
5–60 250 20–25 320–440 18.5–20 170–237 250
5–63 250–350 6.0–8.0 120–230 6–8.0 100–160 180–250
5–60 250–285 10 140 9 33 180
5–62 350–475
15–22 200–320 15–20 245 450–600
0–66 350–440 20–25 380–400 22–23 235–255 450–600
5–63 350–450 20–25 100–395 18.5–23 205–230 450
5–60 250–350 7 180 9 130 400
7–63 550 26 410 22 206 350
5–62 450–500 16 216 14 90 200
2 400 6.8 205 6.5 — —
4 450–520 17.5 285 16.5 155 —
2 610–665 25 380 22 156 400
7–63 250 8–9 75–124 7–9.5 65–95 —
5 250 5 80 4.5 55 180
8–62 660–730 10–18 130–155 15.5 130 500–600

printed circuit boards. P
winding purposes.
Prepregs are used in
parts, sporting goods,
industrial products. Th
their higher specific st
faster manufacturing. T
higher cost. Products m
volume fraction than
Prepregs also provide m
strength properties than

2.5.1 Thermoset Prep

The most common resin
prepregs are generally
a limited shelf life. Room
Usually, the resin is p
Several additives (e.g., fl
to meet various end-u
Thermoset prepregs req
of 1 to 8 hr due to their
needs, rapid-curing the
Thermoset prepregs a
moplastic prepregs. The
hot melt technology. In
solved by a chemical ag
are dipped. Due to gro
vent resulting from this
nology eliminates the u
applied in viscous form
is not easily achievable
Prepregs are generall
molding, and automati
tool, it is cured in the p
final product.

2.5.2 Thermoplastic P

Thermoplastic prepregs
and are generally proc
most common resins a
nylene sulfide, polyimid
posites is much faster
minutes. It is a relative
repregs in roving form are also available for filament
a wide variety of applications, including aerospace
printed circuit boards, medical components, and
e advantages of prepreg materials over metals are
iffness, specific strength, corrosion resistance, and
he major disadvantage of prepreg materials is their
ade with prepreg materials provide a higher fiber
those made by filament winding and pultrusion.
ore controlled properties and higher stiffness and
other composite products.
regs
used in thermoset prepreg materials is epoxy. These
stored in a low-temperature environment and have
-temperature prepregs are also becoming available.
artially cured to a tack-free state called B-staging.
ame retardants, catalysts, and inhibitors) are added
se properties and processing and handling needs.
uire a longer process cycle time, typically in the range
slower kinetic reactions. Due to higher production
rmoset prepregs are being developed.
re more common and more widely used than ther-
y are generally made by solvent impregnation and
the solvent impregnation method, the resin is dis-
ent, creating a low-viscosity liquid into which fibers
wing environmental awareness, disposal of the sol-
process is becoming a concern. The hot melt tech-
se of solvents. In this process, the matrix resin is
. The drawback of this process is that fiber wetting
due to the higher viscosity of the resin.
y used for hand lay-up, roll wrapping, compression
c lay-up processes. Once the prepregs are laid on a
resence of pressure and temperature to obtain the
repregs
have an unlimited shelf life at room temperature
essed at the melting temperature of the resin. The
re nylon, polyetheretherketone (PEEK), polyphe-
e, etc. The process cycle time for thermoplastic com-
than thermoset composites, in the range of a few
ly new technology and provides several processing

and design advantages
tic prepregs are:
• Recyclability
• Good solvent an
• Reduced process
• Higher toughnes
• Indefinite shelf l
• Reshaping and r
• Greater flexibility

in situ

consolidat
• Better repairabili
The disadvantages of
temperatures and press
difficulties because of t
Thermoplastic prepre
hot melt coating techn
Solvent impregnation b
chemical resistance. The
process, wherein fibers a
There are other manufa
der deposition methods
the thermoplastic resin
consolidated under hea
process is clean and sol
of a void-free prepreg.
must be in powder form
charged to form a resin
coated with the charged
fibers are then passed th
a continuous sheet of m

2.6 Preforms

Preforms are feedstock
ment in the form of a t
put in the mold cavity a
composite part. Preform
braiding and filament w
in Figure 2.15.
over thermoset prepregs. The benefits of thermoplas-
d chemical resistance
cycle time
s and impact resistance
ife with no refrigeration
eforming flexibility
for joining and assembly by fusion bonding and
ion
ty potential
thermoplastic prepregs are that they require higher
ures for processing. They provide some processing
heir poor drape capabilities.
gs are manufactured by solvent impregnation and
iques similar to thermoset prepreg manufacturing.
ecomes difficult because thermoplastics offer more
hot melt coating technique is similar to an extrusion
nd resins are extruded simultaneously in sheet form.
cturing methods such as film stacking and dry pow-
for prepreg fabrication. In the film stacking process,
film is stacked together with the reinforcements and
t and pressure to fully imprepregnate the fibers. This
vent-free but requires proper care for the production
In the dry powder deposition technique, the resin
as a starting material. The powder is fluidized and
cloud. The fibers are passed through the cloud and
resin as they get attracted to the fibers. The coated
rough a heat source to fully melt the resin and form
aterial.
for the RTM and SRIM processes, where a reinforce-
hick two- or three-dimensional fiber architecture is
nd then resin is injected into the cavity to obtain the
s are made in several ways. To make a preform by
inding, dry fibers are laid over a mandrel as shown

The braided preform
processes. Braiding can
Helical and longitudina
layers of braided prefo
fiber reinforcements tha
triaxial preforms can be
architecture provides b
braided carbon fiber du
shows a braided carbon

FIGURE 2.15

Braiding of fiberglass preform

FIGURE 2.16

Braided carbon fiber duct pre
Inc.)
is becoming common and is widely used for RTM
be done over a mandrel of nearly any shape or size.
l fiber yarns are interlaced to give a single or multiple
rm. Each pass by the machine produces a layer of
t conforms to the shape of the mandrel. Biaxial and
produced by this method. Three-dimensional fiber
etter interlaminar properties. Figure 2.16 shows a
for an airfoil application. (Courtesy of Fiber Innovations Inc.)
form for an aircraft application. (Courtesy of Fiber Innovations,
ct preform for an aircraft application and Figure 2.17
/epoxy composite spar after resin transfer molding.

Preforms can be of an
the component. Preform
One method of makin
chopped fibers and bin

FIGURE 2.17

Braided carbon/epoxy compo
tions, Inc.)
y shape, depending on the requirements and size of
s are stable and offer a good strength-to-weight ratio.
g a short fiber preform is shown in Figure 2.18. The
site spar after resin transfer molding. (Courtesy of Fiber Innova-
der materials are sprayed into a perforated preform

screen mold. The mold r
in Figure 2.18. With gr
suitable preform thickn
and maintains the shap
to apply the chopped fi
kept stationary and the
Preforms can also be
with woven fabrics, or
This process creates z-d
of complex preforms.

2.7 Molding Comp

There are several types
needs. Molding compo
with resins. In general,
molding processes.

FIGURE 2.18

Schematic of short fiber prefo
Fiber and binder
spraygun
Turntable
Roving
otates but the spraygun remains stationary as shown
adual application of chopped fibers and binders, a
ess builds up. The binder keeps the fibers together
e of the preform. In another version, a robot is used
bers and binders. When a robot is used, the mold is
robot moves around the mold.
made by stitching woven fabrics, by stitching mats
by stitching braided preforms with woven fabrics.
irection reinforcements and allows the manufacture
ound
of molding compounds available to meet various
unds are made of short or long fibers impregnated
they are used for compression molding and injection
rm fabrication.
Air suction
Perforated preform screen
Air inlet port

2.7.1 Sheet Molding

SMC (sheet molding c
containing uncured the
fibers and fillers. It p
chopped glass fibers, in
mally, SMC contains 30
tion of various ingredi
adding filler is to reduc
reduce shrinkage durin
cosity. Styrene is added
prevents premature cur
is added to the compo
from the mold. SMC con
HMC. SMC is a low-co
of composite componen
inates the automotive m
capabilities. SMC comes
of 6 mm. SMC is cut into
for compression moldin
sure are applied to spre
process cycle time for c
The manufacture of s
this process, a resin pas
as described in Table 2.5
metering device. Before
thoroughly mixed. Con
a chopping machine a
Another layer of resin
impregnation. Another
above compound. Thes

TABLE 2.5

Composition of a Ty

Ingredients

Chopped glass fibers
Unsaturated polyester r
Calcium carbonate
Styrene monomer
Polyvinyl acetate
Magnesium oxide
Zinc stearate

-Butyl perbenzoate
Hydroquinone
Compound
ompound) is a sheet of ready-to-mold composites
rmosetting resins and uniformly distributed short
rimarily consists of polyester or vinylester resin,
organic fillers, additives, and other materials. Nor-
% by weight short glass fibers. The typical composi-
ents in SMC is shown in Table 2.5. The purpose of
e the overall cost, increase dimensional stability, and
g molding. Thickener is used to increase resin vis-
for the curing or cross-linking process. An inhibitor
ing of the resin mix. A release agent (mold release)
und for easy release of compression molded parts
taining 50 to 60 weight fraction glass fibers is called
st technology and used for high-volume production
ts requiring moderate strength. Currently, SMC dom-
arket because of its low-cost, high-volume production
in various thicknesses, up to a maximum thickness
a rectangular strip and then kept in the mold cavity
g. During molding, suitable temperature and pres-
ad the charge into the cavity and then to cure it. The
ompression molding is in the range of 1 to 4 min.
heet molding compound is shown in Figure 2.19. In
te (resin, inhibitor, thickener, filler, etc., except fiber)
is placed on a polyethylene moving film through a
placing, all the ingredients of the resin paste are
tinuous strands of glass fibers are chopped through
nd evenly dispersed over the moving resin paste.
paste is placed over dispersed fibers for good fiber
pical SMC
Purpose Weight %
esin
Reinforcement
Base resin
Filler
Co-monomer
Low shrink additive
Thickener
Mold release (lubricant)
Catalyst (initiator)
Inhibitor
30.00
10.50
40.70
13.40
3.45
0.70
1.00
0.25
Trace amount, <0.005 g
Total = 100%
moving polyethylene film is placed on top of the
e top and bottom polyethylene films remain until it

is placed in a compress
handling. The thickness
Instead of chopped gla
fiber (e.g., carbon fibe
through a heated comp
gular shapes for shippi
exposure at around 30°
is called the maturation
satisfactory for its use f
There are three types
form used:
1. SMC-R, for rand
the fiber is writte
fibers (Figure 2.2
2. SMC-CR contain
to random (R) sh
amounts of C an
C30R20 (Figure 2
3. XMC represents
fibers in an X pat
of 5 to 7° (Figure
Table 2.6 provides mec
provides fatigue data fo

2.7.2 Thick Molding C

Thick molding compou
TMC goes up to 50 mm

FIGURE 2.19

Schematic of SMC manufactu
Rovings
Resin
Carrier film
ion mold. These carrier films help in packaging and
of the sheet is controlled by a mechanical adjuster.
ss fibers alone, continuous glass fiber or any other
r) can be added. The complete sheet then passes
action roller and is then rolled up or cut into rectan-
ng. A polyester-based SMC requires 1 to 7 days of
C prior to use in compression molding. This period
period, wherein resin viscosity increases to a level
or the molding operation.
of SMC commonly available, depending on the fiber
omly oriented short fibers. The weight percent of
n after R. For example, SMC-R25 has 25 wt% short
0a).
s continuous (C) unidirectional fibers in addition
ort fibers, as shown in Figure 2.8. The percentage
d R are denoted after the letters C and R as SMC-
.20b).
a mixture of random short fibers with continuous
tern. The angle between cross fibers is in the range
2.20c).
hanical properties of selected SMC and Table 2.7
r selected SMC parts.
ompound (TMC)
ring.
Resin
Carrier film
Compaction rollers
Take-up roll
Chopper
nd (TMC) is a thicker form of SMC. The thickness of
whereas the maximum thickness of SMC is 6 mm.

TMC is used for makin
use several SMC plies.
pliability. In TMC, fibe
whereas in SMC fibers

FIGURE 2.20

Common types of SMC: (a) S

TABLE 2.6

Mechanical Properties of S

Properties SMC-R2

Specific gravity
Tensile modulus,
GPa
Tensile strength,
MPa
Poisson’s ratio
Strain to failure (%)
Compressive
modulus (GPa)
Compressive
strength (MPa)
Flexural strength
(MPa)
In-plane shear
modulus (GPa)
In-plane shear
strength (MPa)
Interlaminar shear
strength (MPa)
1.83
13.2
82.4
0.25
1.34
11.7
183
220
4.5
79
30

Source:

From Reigner, D. A. an

1979.
(a)
g thicker molded parts. TMC eliminates having to
Due to its greater thickness, TMC provides reduced
MC-R; (b) SMC-CR; and (c) XMC.
ome Selected SMC (Glass Fibers in Polyester Resin)
5 SMC-R50 SMC-R65 SMC-C20R30 XMC-31
1.87
15.8
164
0.31
1.73
15.9
225
314
5.9
62
25
1.82
14.8
227
0.26
1.63
17.9
241
403
5.4
128
45
1.81
21(L), 12(T)
289(L), 84(T)
0.30(LT), 0.18(TL)
1.7 (L), 1.6(T)
20(L), 12(T)
306(L), 166(T)
640(L), 160(T)
4.1
85
41
1.97
36(L), 12(T)
561(L), 70(T)
0.31(LT), 0.12(TL)
1.7(L), 1.5(T)
37(L), 14(T)
480(L), 160(T)
970(L), 140(T)
4.5
91
55
d Sanders, B. A., Proc. Natl. Tech. Conf., Society of Plastics Engineers,
(b) (c)
rs are randomly distributed in three dimensions,
are in two dimensions.

2.7.3 Bulk Molding C

Bulk molding compoun
It is also known as dou
mixing the resin paste w
or rope form. The extru
ment. BMC generally c
resin. The fiber length ra
fraction and shorter fibe
properties than SMC co

TABLE 2.7

Fatigue Data for Sele

Material
Fat
Stre
at 2
(M

SMC-R25
SMC-R50
SMC-R65
SMC-C20R30(L) 1
SMC-C20R30(T)
XMC-31(L) 1
XMC-31(T)

Source:

From Reigner, D

Plastics Engineers, 1979

FIGURE 2.21

Various forms of molding com
ompound (BMC)
d (BMC) is a compound that is in log or rope form.
gh molding compound (DMC). BMC is obtained by
ith fibers and then extruding the compound in log
ded part is cut to length, depending on the require-
ontains 15 to 20% fiber in a polyester or vinylester
nges from 6 to 12 mm. Due to the lower fiber volume
cted SMC Parts
igue
ngth
3°C
Pa)
Fatigue
Strength
at 90°C
(MPa)
Ratio of Fatigue
to Ultimate
Static Strength
(23°C)
Ratio of Fatigue
to Ultimate
Static Strength
(90°C)
40 25 0.49 0.55
63 53 0.38 0.41
70 35 0.31 0.28
30 110 0.45 0.44
44 35 0.52 0.43
30 85 0.23
0.18
19 27 0.15 0.26
. A. and Sanders, B. A., Proc. Natl. Tech. Conf., Society of
.
pounds. (Courtesy of Cytec Fiberite.)
r length, BMC composites provide lower mechanical
mposites.

2.7.4 Injection Molda

Injection molding is a w
product fabrication. Th
low-cost fabrication of
stiffness and strength, r
Injection molding com
thermoplastic resins. Th
the fiber strand through
flow die induces shear
wet-out and dispersion
lengths of around 10 m
the range 0.2 to 6 mm lo
the molding operation.
to make pellets. A wide
be used to make injectio
compound (15 mm fibe
Thermoset molding c
process. The fiber length
typical resins used are
reduces to 0.1 to 0.5 m
compounds are shown

2.8 Honeycomb an

These materials are gen
two thin high-strength f
an adhesive strong eno
The honeycomb materi
as well as providing str
away from the neutral a
The difference between
structure, the web is sp
torsional rigidity; wher
providing less torsiona
highest stiffness-to-weig
Aluminum, Nomex
Figure 2.22. These hone
of honeycomb cores ar

8 ft size having 0.125 t
used are 0.125 to 1.0 in
Nomex core is mostly h
a circular shape.
ble Compounds
idely used manufacturing method for thermoplastic
is method provides increased production rates and
parts. Because unfilled thermoplastics have lower
einforcements are made by adding short fibers.
pound (Figure 2.21) can be made with thermoset or
ermoplastic molding compound is made by passing
a die similar to the pultrusion process. The counter-
that lowers the resin viscosity and enhances fiber
. The rod-like structure is then pulled and cut into
m in pellet form. The molded part contains fibers in
ng. The reduction in fiber length takes place during
Glass, carbon, and aramid fibers can be reinforced
variety of resins (e.g., nylon, PPS, PP, PE, etc.) can
n moldable thermoplastic parts. A long fiber-molded
r length) is also available.
ompounds are also used for the injection molding
is generally 1.5 mm for short fiber composites. The
epoxy, phenolics, polyester, etc. The fiber length
m after the molding process. Some of the molding
in Figure 2.21.
d Other Core Materials
erally used for sandwich structures as cores between
acings. These materials are joined with facings using
ugh to transfer the loads from one face to another.
al acts like a web of I-beams, taking the shear loads
uctural rigidity by keeping high-strength materials
xis where tensile and compressive stresses are high.
sandwich structure and I-beam is that in sandwich
read over the entire cross section, providing high
eas in I-beam, the web is only in the middle, thus
l rigidity. The sandwich construction provides the
ht ratio and strength-to-weight ratio.
, and thermoplastic honeycombs are shown in
ycombs can be cut in any shape, however, flat sheets
e mostly used. A typical flat sheet comes in a 4 ¥
o 12 in. thickness. The cell sizes most commonly
. diameter. The shape of a cell in an aluminum and
exagonal, whereas thermoplastic honeycombs have

Honeycomb materials
nication, sporting good
provide predictable cra
resistant parts. These m
communications rooms
The repetitive cellular s
signals across a wide fr

are used for the manufa
properties of selected ho
honeycomb materials a
polypropylene (Figure 2

FIGURE 2.22

Commonly used aluminum, N
are used in aircraft, transportation, marine, commu-
s, and many other industries. Honeycomb materials
sh behavior and are used for the design of crash-
aterials are used for the design of computer and
because of their radiation shielding characteristics.
tructure acts as a myriad of waveguides, attenuating
equency range.3 Metallic and nonmetallic materials
cture of honeycomb cores (Figure 2.22). Some of the
neycomb cores are given in Table 2.8. Most prevalent
re made of aluminum, Nomex, polycarbonate, and
omex, and thermoplastic honeycombs. (Courtesy of Alcore, Inc.)
.22).

There are two major
expansion and corrugat
used for making alumin
cess, sheets of material a
adhesive nodelines are
bonding. The stack of s
are cut from the block a
shape.
In the corrugation me
rugation form using co
together, bonded, and c
the desired shape and s
Other than honeycom
wood, and foam cores a
a wide variety of open a
or rubbery. Foams can
resin by various techniq
able bead process, etc.
the resin to decrease its
purpose of the foam is t
structural members wi
member.

TABLE 2.8

Physical Properties of S

Material
Cel
Diam
(in

5052 Aluminum
5052 Aluminum
3003 Aluminum
3003 Aluminum
Polycarbonate
Polycarbonate
Polyetherimide
Aramid (Nomex)
Aramid (Nomex)
Aramid (Nomex)
Glass-reinforced
polyimide
Glass-reinforced
phenolic
0.12
0.12
0.25
0.5
0.12
0.25
0.12
0.12
0.12
0.25
0.18
0.18
methods for the manufacture of honeycomb cores:
ion. The expansion method is more common and is
um and Nomex honeycombs. In the expansion pro-
re stacked together in a block form. Before stacking,
printed on the sheets to obtain interrupted adhesive
heets is then cured. Slices of appropriate thickness
nd then expanded to obtain the desired cell size and
thod, the sheet of material is transformed into cor-
rrugating rolls. The corrugated sheets are stacked
ured. Honeycomb panels are cut from the block into
ize without any expansion.
b materials, core materials such as balsa wood, ply-
re available to obtain sandwich structures. There are
nd closed cell foams available that are rigid, flexible,
be made using thermosetting resin or thermoplastic
ues, including gas injection, blowing agent, expand-
All these processes supply gas or blowing agent to
density by forming closed or open gaseous cells. The
o increase the bending stiffness and thickness of the
thout proportionately increasing the weight of the
ome Selected Honeycomb Materials
l
eter
.)
Density
(lb/ft3)
Max.
Service
Temp.
(°F)
Stabilized
Compressive
Modulus
(ksi)
Stabilized
Compressive
Strength
(psi)
5
5
5
5
5
5
75
75
8.1
3.1
5.2
2.5
7.9
3.0
5.1
8.0
4.0
3.1
8.0
5.5
350
350
350
350
200
200
—
350
350
350
500
350
350
75
148
40
55
15
32
80
28
21
126
95
1470
275
625
165
695
110
580
1900
560
285
1300
940

References

1. Mazumdar, S.K. and
hot gas aided therm

Mater.,

9, January 19
2. Reigner, D.A. and S
tinuous and random

Plastics Engineers, 1
3. English, L.K., Hone

p. 29, January 1985.

Questions

1. Why do thermop
mosets?
2. Why is it easier to
3. Compare the per
and aramid fiber
erties are impro
break?
4. What are the co
composites indu
5. Which thermose
perature compos
6. What are the dif
Write the pros an
7. Write down the
prepregs?
8. How are short fi
9. Why are honeyc
10. List different typ
Hoa, S.V., Determination of manufacturing conditions for
oplastic tape winding technique, J. Thermoplastic Composite
96.
anders, B.A., A characterization study of automotive con-
glass fiber composites, Proc. Natl. Tech. Conf., Society of
979.
ycomb: million-year-old material of the future, Mat. Eng.,
lastics have shorter processing times than ther-
process with thermosets than with thermoplastics?
centage of elongation at break for glass, graphite,
s with aluminum and steel. What material prop-
ved with increase in percentage elongation at
mmonly used fibers and resins in the thermoset
stry?
t and thermoplastic resins are used for high tem-
ite applications?
ferences between woven and non-woven fabrics?
d cons of these fabrics?
composite manufacturing techniques
that use
ber preforms manufactured?
omb and core materials used?
es of molding compounds?

Material Selec

3.1 Introduction

The behavior and perfor
used in making the par
the design and manufa
choice for a given appli
selection. Depending on
cost, quality, and perfo
becomes vital for civil
almost 50% of the total
as computers, material
volume used in civil and
opportunities for mater
This chapter illustrate
methods are important
Cost vs. property analy
expert systems are desc
material is selected for
ations begin.

3.2 The Need for M

With the technological
are being developed an
steel and aluminum w
longer the case. With gr
opportunities offered by
rials can cause decrease
tion Guidelines
mance of a product depend on the types of materials
t. There are more than 50,000 materials available for
cture of a product. Every material cannot be a right
cation; therefore, there is a need for suitable material
the selection of a material, the design, processing,
rmance of the product change. Material selection
and mechanical structures where material cost is
product cost. For microelectronic applications such
cost is almost 5% of the product cost. Because the
mechanical structures is very high, there are greater
ial innovations.
s how material properties and systematic selection
to quick and effective selection of a suitable material.
sis, a weighted property comparison method, and
ribed as tools for material selections. Once a suitable
an application, design and manufacturing consider-
aterial Selection
advancements, new material systems and processes
d are growing faster than ever before. In the past,
ere more dominant for product design. This is no
owing awareness and customer needs, ignorance of
advanced material systems such as composite mate-
d competitiveness and can lead to loss of market.

With the increase in cu
competition among com
and be at the cutting e
and advanced materials
new laws for a better e
automakers to develop
(almost 3 times that of
ronmental awareness, l
ious industry sectors.
Material selection for
efficiency. The aerospac
weight materials. Cons
factor, are driven by cos
high performance and
sizes lightweight and
weight and high-per
opportunities for comp
solutions to fulfill the n

3.3 Reasons for M

There are two major r
material selection proce
1. To redesign an ex
increased reliabil
2. To select a mater
In either case, mere mat
be redesigned for the s
the material’s propertie
material is substituted f
redesigned to obtain th
material is not selected
compared to steel and
materials costs should
actual comparison, the p
parts made by injection
by the die casting or sa
tions to get the final pa
golf shafts should be
stomer demand for higher performance and quality,
panies has increased. To capture the global market
dge of the technology, companies are utilizing new
for increased performance. Government is passing
nvironment. The Federal Government encouraged
vehicles with fuel efficiency of 80 miles per gallon
existing mileage). In light of global needs and envi-
ightweight materials are gaining importance in var-
the automotive market is driven by cost and energy
e market emphasizes high performance and light-
umer products, where performance is not a critical
t and handling. The sporting goods market demands
lightweight materials. The marine industry empha-
corrosion-resistant materials. This interest in light-
formance materials has given rise to several
osites technology. Composite materials can provide
eeds of various industrial sectors.
aterial Selection
easons why an engineer becomes involved in the
ss.
isting product for better performance, lower cost,
ity, decreased weight, etc.
ial for a new product or application.
erial substitution is not sufficient. The product must
elected material to utilize the maximum benefits of
s and processing characteristics. When a composite
or a steel or aluminum product, the part needs to be
e cost and weight benefits. Many times, a composite
for an application because of higher material cost,
aluminum on a weight basis. Such a comparison of
be avoided in the selection of a new material. For
roduct’s final cost should be compared. For example,
molding should be compared with the parts made
nd casting process, including the machining opera-
rt. Similarly, the roll wrapping process for making
compared with the filament winding process; this

comparison should be b
materials. For the filam
times cheaper than the
process; but for large p
wrapping process is sel

3.4 Material Prope

Materials data enters a
of accuracy required on
In the initial stage of the
for wide range of mate
Table 3.1 and Tables 2.1
the various types of com
the preliminary assessm
designer identifies whic
example, for a certain ap
and for another applica
for a manufacturing pr
more appropriate than t
selects a particular raw
key characteristics of t
material is selected for
following parameters:
• Type of prepreg:
• Fiber type (carbo
• Woven pattern (p
• Width of the tap
• Resin content
• Areal weight
• Ply physical and
Similarly the manufac
processing temperature
application.
Materials property inf
suppliers’ brochures, an
data is given on the prop
design process, more d
precisions is required.
ased on final product cost, not on the cost of initial
ent winding process, the raw material cost is 3 to 8
graphite/epoxy prepreg used in the roll wrapping
roduction volume and higher performance, the roll
ected for making golf shafts.
rty Information
t various stages of the design process, but the level
material property information differs at each stage.
design process (conceptual stage), approximate data
rials is gathered and design options are kept open.
and 2.2 in Chapter 2 provide basic information about
posite materials. This information can be helpful in
ent of these materials. In the preliminary stage, a
h matrix material and fibers are more suitable. For
plication, polyester resin might be a suitable choice;
tion, epoxy may be a more suitable choice. Similarly,
ocess, one specific type of material system may be
he other. For a manufacturing process, if the engineer
material, the engineer needs to clearly write down
he selected raw material. For example, if prepreg
an application, then the designer has to identify the
unidirectional or woven fabric prepregs
n, glass, Kevlar, etc.)
lain weave, satin weave, etc.)
e
mechanical properties
turing engineer has to specify tack, drape, cure cycle,
, gel time, flow characteristics, and more for the
ormation can be obtained from published literature,
d handbooks. In the published literature, single-value
erty without any standard deviation. During the final
etailed information on material property with high

3.5 Steps in the M

There are four steps inv
material of choice.

3.5.1 Understanding

The first step in identif
cost, weight, service, pe
benefits a material can
cation. For example, w
whereas weight is critica
the wear resistance req
application, wear resista
to prioritize the require
selection process. Some
ing material selection p
1. Strength
2. Impact resistance
3. Temperature resi
4. Humidity, chemi
5. Process
6. Production rate
7. Cost

3.5.2 Selection of Po

Based on the requireme
facturing processes tha

TABLE 3.1

General Properties of T

Property T

Fiber volume
Fiber length
Molding time
Molding pressure
Material cost
Safety/handling
Solvent resistance
Heat resistance
Storage life
Med
Cont
Slow
Low
Low
Good
High
Low
Good
refr
aterial Selection Process
olved in narrowing the list of materials to a suitable
and Determining the Requirements
ying a material is to define the requirements (e.g.,
rformance, etc.) of a product. There may be several
offer but some requirements are critical to the appli-
eight might not be critical for a consumer product,
l for an aerospace part. Similarly, for one application,
uirement may be very high, whereas for another
nce may be of no concern. Therefore, it is important
ments of a product in the beginning of a material
of the requirements that need to be considered dur-
rocess are:
stance
cal and electrical resistance
ssible Materials
hermoset and Thermoplastic Composites
hermoset Composites Thermoplastic Composites
ium to high
inuous and discontinuous
: 0.5 to 4 h
: 1 to 7 bars
to high
to high
(6 to 24 months with
igeration)
Low to medium
Continuous and discontinuous
Fast: less than 5 min
High: greater than 14 bars
Low to medium
Excellent
Low
Low to medium
Indefinite
nts of an application, possible materials and manu-
t meet minimum or maximum requirements of the

application are determi
cussed simultaneously
rial systems. For examp
a choice of compression
minimum or maximum
possess and should res
of this screening phase
ular material and the
Selection of potential m
from material suppliers

3.5.3 Determination

Once a list of materials
task is to determine the
To do this, methods d
techniques can greatly
In the conceptual des
ufacturing method are
innovative designs. Des
composite driveshaft (F
designer can look at pu
processes for weight, co
num can also be consid
composite material choi
rior dampening charact
and eliminate harmonic
above utilize different t
system may not be su
example, glass fiber an
pultrusion process, a g
filament winding indus
for the roll wrapping pr
mon for the RTM proces
or RTM or pultrusion p
for greater weight savin

FIGURE 3.1

Composite driveshaft.
Metal end
ned. Materials and manufacturing processes are dis-
because they go hand in hand with composite mate-
le, if SMC is selected, then the designer is left with
molding. To narrow the choice, one should set the
requirements that the material and the process must
ult in a positive “yes” or “no” answer. The purpose
is to obtain a definite answer as to whether a partic-
process should be considered for the application.
aterials is done from material databases obtained
and handbooks.
of Candidate Materials
based on the above guidelines is created, the next
candidate materials best suited for the application.
iscussed in Section 3.6 should be consulted. These
help the designer to narrow down the choices.
ign phase, more than one material system and man-
selected to provide a wide choice of creative and
ign options are kept open. For example, to make a
igure 3.1) for a truck or racing car application, the
ltrusion, filament winding, RTM, and roll wrapping
st, and performance comparisons. Steel and alumi-
ered a suitable choice; but for the present analysis,
ces are discussed. Composite driveshafts offer supe-
eristics, reduced rotating weight, greater fatigue life,
whipping. The manufacturing processes discussed
ypes of material systems, and one type of material
itable for all of the manufacturing processes. For
d vinylester resin systems are more suitable for a
lass and polyester combination is common in the
try, graphite/epoxy prepreg is the basic raw material
ocess, and preform and vinylester systems are com-
s. Instead of glass fibers in the above filament winding
Composite tube Metal end
rocess, an option of carbon fibers can be considered
g and better vibration dampening characteristics. The

costs per pound of thes
of these material syste
with the requirements
driveshaft in the presen
These metal ends can b
processes. For example,
in the pultrusion proce
in the filament winding
The cost, weight, and p
concepts will vary and t
the right selection of m
and other analyses must
element analysis (FEA)
and time associated with
approach must be avoi
ments will greatly help

3.5.4 Testing and Eva

After selecting the cand
ufacturing processes, p
the design. Depending
parts to be tested shoul
erally require more test
under various service c
breaking of the part may
number of tests are req
For critical application
the behavior of the part
driveshaft needs to be t
exposures, and tempera
tests are conducted und
used) is investigated f
cycling and stone impin
All of the above tests a
test procedure is create
sequence of the above e
results obtained provide
strength has to be meas
thermal cycling of the a
then bond strength — in
tests is to generate sta
expected during the ser
e material systems are different. The pros and cons
ms and manufacturing processes must be checked
discussed in Sections 3.5.1 and 3.5.2. Moreover, the
t analysis has two metal ends as shown in Figure 3.1.
e incorporated differently for these manufacturing
adhesive bonding is most suitable for end connection
ss, while mechanical locking may be more suitable
process and insert molding may be the best in RTM.
erformance characteristics of each of these design
he engineer must look at all of these options to make
aterial systems and manufacturing processes. Stress
be performed to evaluate each design concept. Finite
software and other tools can greatly reduce the cost
the product development phase. A make-and-break
ded. A good understanding of the product require-
in making the right material and processing choices.
luation
idate materials for the various types of feasible man-
rototype parts are made and then tested to validate
on the seriousness of an application, the number of
d be decided. Aerospace and automobile parts gen-
s to ensure that the part functions safely and reliably
onditions. For some consumer products, for which
not result in physical damage or injury, a minimum
uired.
s, a large property database is created to understand
under various service conditions. For example, the
ested for automotive fluid exposures, water and salt
ture extremes of –40 and +150°C. Static and dynamic
er these conditions. The behavior of the adhesive (if
or these service conditions. The effect of thermal
gement on the performance should be understood.
re performed separately; but in some cases, a new
d to simulate the worst-case scenario. For this, a
xposures are determined in such a way that the test
a worst performance. For example, if adhesive bond
ured for the assembly, then to get the worst result,
ssembly is done first, then stone impingement, and
stead of bond strength first. The purpose of all these
tistically reliable test results under the conditions
vice life of the product.

3.6 Material Selec

There is no standard tec
for an application. Som
before in similar condit
In the current competit
overlook new emergin
competitive position. Th
all possible opportuniti
for the reduction of man
performance. This secti
evaluation of a suitable

3.6.1 Cost vs. Proper

Cost is a crucial factor
compares the material
The property could b
strength, fatigue, creep,
application. The metho
rials to meet the desire
of the material. For st
required to carry the lo
specific gravity, the we
4 times heavier than c
weight savings as comp
Because cost is so imp
should be taken to dete
techniques are discussed
to consider total life-cy
cost includes not only
cost for serviceability, m
In this section, only
requirement. For an ap
might be tensile strengt
creep, or any combinat
factor for the selection
materials of choice are d
Suppose materials A an
tensile strengths
are

areas are A

and A

, res
load P, then the cross-se
tion Methods
hnique used by the designer to select a right material
etimes, a material is selected based on what worked
ions or what a competitor is using in their product.
ive market, this short-cut method may cause one to
g technologies and may put the product in a less
e job of materials and design engineers is to consider
es to utilize new material systems and technologies
ufacturing cost and weight for the same or increased
on presents some material selection methods for the
material.
ty Analysis
in a material selection process. The present method
cost for equivalent material property requirements.
e tensile strength, compressive strength, flexural
impact, or any other property that is critical to the
d determines the weight required by different mate-
d property. From the weight, it determines the cost
ructural applications, the volume of the material
ad is determined and then, by multiplying with the
ight is determined. For equal volumes, steel is 3 to
omposites; thus, composites can offer significant
ared to steel if properly designed and manufactured.
ortant in any decision-making process, proper care
rmine the actual cost of the product. Cost-estimating
in detail in Chapter 11. Many times, it is appropriate
cle cost as the basis for decision-making. Life-cycle
material cost and manufacturing cost, but also the
aintainability, and recycling.
material cost is compared for equal performance
plication, the most critical performance requirement
h, compressive strength, fatigue strength, impact, or
ion of these. If tensile strength is the determining
of a material, then the weight required by different
etermined to have the same tensile strength values.
d B are selected for comparison purposes and their
and sB, densities are rA and rB, and cross-sectional
pectively. If the member is designed to carry an axial
ctional area required by beam A will be:

and beam B will be:
If the member is a solid
be:
and
or
The ratio of the diamet
For equal lengths of
above. The weight ratio
If the cost per unit we

then the ratio of total m

In this example, a cost
material. Similarly, it ca
fatigue strength, etc.
(3.1)
(3.2)
circular rod, then the corresponding diameters will
(3.3)
(3.4)
(3.5)
ers will be:
(3.6)
rod L, the volume ratio of the rod will be same as
will be:
(3.7)
ight of materials A and B is CA and CB, respectively,
aterial costs TA and TB will be:
(3.8)
comparison is done for the tensile strength of the
n be done for design strength, compressive strength,
A
P
A
A
=
s
A
P
B
B
=
s
D
P
A
A
2 4
=
ps
D
P
B
B
2 4
=
ps
P D DA A B B= =
p
s
p
s
4 4
2 2
D
D
A
B
B
A
=
Ê
Ë
Á
ˆ
¯
˜
s
s
1
2
W
W
D L
D L
A
B
A A
B B
A
B
B
A
= =
r p
r p
r
r
s
s
( / )
( / )
4
4
2
2
T
T
C
C
W
W
C
C
A
B
A
B
A
B
A
B
A
B
B
A
= =
r
r
s
s

Similarly a beam can
ness. For example, defl
center is given by:
where P is the load app
E is the modulus of th
cross-section. The determ
and introductory textbo
is constructed of 16 pli
modulus along the long

following relation:
where E

is the modulus
tion and E

is the modu
ular to fiber) direction, G

ratio, and

is the fiber o

The stiffness of the be
For the same length
Equation (3.11). Therefo
The cross-section of t
any other shape. I for
materials book or mach
where b is the width a
For the same width, thi
1
Ex
=
co
be designed for bending stiffness or torsional stiff-
ection of a simply supported beam loaded at the
(3.9)
lied at the center, L is the total length of the beam,
e composite, and I is the moment of inertia of the
ination of E for a composite beam is given in design
oks on composite materials. For example, if a beam
es with ±45° fiber orientations, then the equivalent
itudinal direction (x-direction) is determined by the
(3.10)
of the composite along the longitudinal (fiber) direc-
lus of the composite along the transverse (perpendic-
LT is shear modulus of the composite, nLT is Poisson
rientation along the x-axis (tube length direction).
am may be given by:
(3.11)
of beam, stiffness is proportional to EI as shown in
re, for two material systems A and B,
(3.12)
he beam could be rectangular, I-shaped, circular, or
various cross-sections are given in any strength of
inery handbook. For a rectangular shape,
(3.13)
nd h is the height or thickness of the cross-section.
ckness h can be compared as:
(3.14)
d =
PL
EI
3
48
1
4
1 2
2
4 4
2
E E G EL T LT
LT
L
+ + -
Ê
Ë
Á
ˆ
¯
˜
s sin
sin
q q
n
q
P EI
Ld
=
48
3
E I E IA A B B=
I
bh
=
3
12
h h
EA
=
Ê ˆ
1
3
EB A BË
Á
¯
˜

Relative weight can b
Total material cost ca
For various other prop
noted here that specific
eters in tension or com
stiffness or strength. Oth
properties (e.g., chemic
durability) that could b
to be given sufficient co
applications, strength, s
material selection. Othe
wear resistance can be i
This secondary operatio
cost. It is beneficial to
operations. Unlike many
chemical resistance wit
resistance. Chrome plati
on composite surfaces f

3.6.2 Weighted Prope

In many circumstances,
cost, serviceability, and
cation. The level of imp
cations. For example,
applications and weigh
tions. In commercial p
$100 to $1000 cost savin
of weight saving transla
industry, a pound of w
This method is suitable
material selection purp
e written as:
(3.15)
(3.16)
n be compared as:
(3.17)
erties, similar relationships can be determined. It is
stiffness and specific strength are important param-
pression for comparison purposes, and not just the
er than strength and stiffness, there are several other
al resistance, corrosion resistance, wear resistance,
e important to an application. These properties need
nsideration in material selection. For many structural
tiffness, weight, and cost are important features in
r secondary features such as corrosion resistance or
ncorporated by providing a coating to the structure.
n on the surface of the structure requires additional
have these features without performing secondary
metals, composites can provide good corrosion and
hout any coating. Composites are coated for wear
ng, ceramic coating, and teflon coating can be applied
or additional surface characteristic requirements.
rty Comparison Method
there are several factors (e.g., weight, performance,
machinability) that may be important for an appli-
ortance of each factor is different for different appli-
product cost is given more weight in automobile
t is given higher consideration in aircraft applica-
lanes, a pound of weight saving translates into a
gs. In space applications such as a satellite, a pound
tes into about $10,000 cost savings. In the automotive
eight saving translates into $5 to $10 cost savings.
W
W
h
h
A
B
A A
B B
=
r
r
W
W
E
E
A
B
A
B
B
A
=
Ê
Ë
Á
ˆ
¯
˜
r
r
1
3
T
T
C
C
W
W
C
C
E
E
A
B
A
B
A
B
A
B
A
B
B
A
= =
Ê
Ë
Á
ˆ
¯
˜
r
r
1
3
for cases in which more than one factor is used for
oses.

According to this
me
depending on its import
in different units, each
range. This is done by
on the type of property

3.6.2.1 Scaling for M

There are material pro
elongation, that are de
properties are scaled in

3.6.2.2 Scaling for M

There are properties, su
a low value in a design

3.6.2.3 Scaling for N

There are properties, su
ability, machinability, re
value. Such properties a
Once material proper
is determined as follow
where

is weighting fa

of all the properties un

TABLE 3.2

Scaling of Nonquan

Property

Chemical resistance
Subjective rating
Scaled property
a = scaled prope
a = scaled prop
thod, each property is assigned a certain weight,
ance during service. Because properties are measured
property is normalized to get the same numerical
a scaling method in the following ways, depending
requirement.
aximum Property Requirement
perties, such as strength, stiffness, and percentage
sired in a structure to be a maximum value. Such
the range of 0 to 100 in the following way:
(3.18)
inimum Property Requirement
ch as cost, density, and friction, that are required as
. Such properties are scaled as follows:
(3.19)
onquantitative Property
ch as wear resistance, corrosion resistance, repair-
cyclability, that cannot be quantified as a numerical
re given subjective ratings as shown in Table 3.2.
ties are scaled, the performance index of a material
s:
(3.20)
titative Property
Materials under Consideration
A B C D E
Poor
1
20
Good
3
60
Excellent
5
100
Satisfactory
2
40
Very Good
4
80
= ¥rty
Numerical value of a property
Highest value in the same category
100
= ¥erty
Lowest value in the same category
Numerical value of a property
100
g a=
Â
wi i
ctor, a is a scaled property, and i is the summation
der consideration.

Example 3.1

Evaluate alternative ma
suspension system on t
and mass. A manageme
flexural strength (0.15),

SOLUTION:

Various material syste
(glass/Ep), aluminum (
shown in Table 3.3. The
for this application. The
to each property. Befor
materials to meet some
temperature resistance
meet these requiremen
ite/epoxy has the highe
candidate for the leaf sp

3.6.3 Expert System f

Thousands of material
material selection. This
of alternative materials
developed for composi
feeds in the service co
range, chemical resista
toughness, strength, etc
expert system provides
Unlike metals, a large d
for various conditions
designers and fabricat

TABLE 3.3

Material Evaluation for A

Material

Go/No-Go Scre
Corrosion
Resistance

T
Re

Gr/Ep
Glass/Ep
304 Steel
6061 Al
S
S
S
S

S = satisfactory.
terials for a leaf spring to be used in a vehicle as a
he basis of flexural strength, fatigue strength, cost,
nt team gives weight to various properties as follows:
fatigue strength (0.2), cost (0.25), and mass (0.4).
ms such as graphite/epoxy (Gr/Ep), glass/epoxy
Al), and steel are considered for this application, as
analysis shows that graphite/epoxy is the best choice
result can vary, depending on the weight assigned
e evaluation, go/no-go screening is done for these
other requirements such as corrosion resistance and
of –40 to +120°C. In this case, all the above materials
ts satisfactorily. For the present example, graph-
st performance index and is thus the most suitable
ring.
or Material Selection
choices are available to an engineer to assist in right
reveals the need for an expert system for the selection
for a given application. Few expert systems are being
te material selection. In an expert system, the user
ndition requirements (e.g., operating temperature
nce, fluid exposure, percent elongation, fracture
.) and based on the available material database, the
material systems that are suitable for the application.
atabase for the performance of composite materials
utomotive Leaf Spring
Scaled Property
Performance
Index
ening Flexural
Strength
(0.15)
Fatigue
Strength
(0.20)
emp.
sistance
Cost
(0.25)
Mass
(0.40)
S
S
S
S
100
85
80
60
100
90
60
40
30
50
100
60
100
80
40
60
82.5
75.25
65
56
is not available. Raw material suppliers provide
ors with a list of basic material properties. The

datasheet is typically ge
in their laboratory. Thes
rials but not for final se

Bibliography

1. Ashby, M.F., Materi

June 1989.
2. Dieter, G.E.,

Enginee

Hill, New York, 198
3. Crane, F.A.A. and C

terworths, London,
4. Smithells, C.J., Ed.,

5. Harper, C.A., Ed.,

1975.
6. Morrell, R.,

Handboo

Her Majesty’s Statio

Questions

1. Why do materia
hand in hand?
2. Under what circu
3. What are the ste
application?
4. An engineer has
select for an app
and machinabilit
and select the be
nerated by testing standard coupons manufactured
e datasheets are useful for initial screening of mate-
lection.
als selection in conceptual design, Mater. Sci. Technol., 5,
ring Design: A Materials and Processing Approach, McGraw-
3.
harles, J.A., Selection and Use of Engineering Materials, But-
1984.
Metals Reference Book, 6 ed., Butterworths, London, 1984.
andbook of Plastics and Elastomers, McGraw-Hill, New York,
k of Properties of Technical and Engineering Ceramics, Part 1,
nery Office, London, 1985.
ls and composites manufacturing processes go
mstances does a search for new materials start?
ps involved in selecting a best material for an
three materials — A, B, and C — from which to
lication. The selection criteria are specific strength
y. How would you quantify the selection process
st material from among these three?

Product Devel

4.1 Introduction

Every year, hundreds o
marketplace. Material s
resins, and prepreg mat
not available in the pa
epoxy-based prepregs w
available. Preform manu
ogies and preform mate
comb and core supplie
market needs. Sporting
industries are launching
competitive position. Th
num parts with compos
space industry is utiliz
payload capacities and
The need for new m
with the improvement i
panies are struggling to
by improving their p
demanding better prod
icantly. There has been
ment cycle time. It is sa
first onto the market ge
Understanding the pr
fabrication of a good q
puter companies follow
product/model or a sp
product development p
ments of a product dev
opment
f new materials and products are launched into the
uppliers are coming up with new reinforcements,
erials to meet various customer needs. The materials
st have become the material of choice today. New
ith a shelf life of 1 year at room temperature are
facturers are coming up with new braiding technol-
rials for increased manufacturing feasibility. Honey-
rs are introducing new core materials to meet new
goods manufacturers, boat builders, and consumer
new products into the marketplace to maintain their
e automotive industry is replacing steel and alumi-
ite materials for fuel and weight savings. The aero-
ing more and more composite materials to increase
fuel savings.
aterial/product development has increased rapidly
n technology and globalization of the market. Com-
keep their competitive position in the marketplace
roduct quality and performance. Customers are
ucts at lower cost. Product life has decreased signif-
greater demand for reducing the product develop-
id that the companies that introduce a new product
t more than 50% of the market share.
oduct development process is very important in the
uality part. Major automotive, aerospace, and com-
a systematic approach for the development of a new
ecific part. Product fabrication is one element of a
rocess. This chapter explains all the important ele-
elopment process.

4.2 What Is the Pro

Product development is
design and manufacturi
managing mutual depen
including the design, m
posal or recycle stages. T
to team members for the
and manufacture the pr
launching of a product, f
ment consists of materia
ufacturing and assembly
successful launching of t
scenario, the sales or m
product. They study an a
product development te
product from the market
ing on the product need,
Engineers have many cho
materials. Refer to Chap
material selection guidel
selection of a manufactur
require different initial r
into consideration the pr
material, and manufact
made using the selected
tested and validated to
various phases of produ
The goals of a product
maximize product qualit
and minimize lead times
cycle time. A compressed
from diverse groups su
product engineering, rel
tically reduces the produ
managerial and engineer
the functional, performa

4.3 Reasons for Pr

Product development a
create growth in the com
a new product.
duct Development Process
a process for translating customer needs into product
ng. A broader view of product development involves
dencies between all stages of the product life cycle,
anufacturing, distribution, technical support, and dis-
he product development process provides a roadmap
activities and deliverables required to design, develop,
oduct. It is a systematic approach for the successful
rom concept initiation to marketing. Product develop-
l selection, product design, selection of the right man-
techniques, prototyping, testing and validation, and
he product into the marketplace. In a typical industrial
arketing department identifies a market need for a
pplication and pass the application requirement to the
am (PDT). The PDT collects information about the
ing team or by talking directly to the customer. Depend-
suitable materials are then selected for the application.
ices from which to select the right resin and reinforcing
ters 2 and 3 for various types of raw materials and
ines. The selection of a material is also affected by the
ing process because different manufacturing processes
aw materials. The product is then designed by taking
os and cons of a manufacturing process. Once design,
uring processes are selected, prototype parts can be
manufacturing processes. Prototype parts are then
meet the identified service and consumer needs. The
ct development are described in detail in Section 4.7.
development activity are to minimize life-cycle costs,
y, maximize customer satisfaction, maximize flexibility,
. Today’s hot topic is to compress product development
product development process incorporates specialists
ch as design, manufacturing, marketing, purchasing,
iability, and sometimes customers. This strategy dras-
ct development cycle time. This chapter focuses on the
ing steps needed during product development to meet
nce, and customer requirements of the product.
oduct Development
ctivities are undertaken to increase market share and
pany. Following are the main reasons for launching

1. To find new busi
2. To add features a
to increase mark
3. To retain custom
4. To attract more c
There are so many fe
features cannot be incor
every customer’s requir
for all the features. Ther
of features for different
reader get a good comb
• List all buying co
• Separate the list
to have, (3) nice
• Rate each feature
This analysis will help t
groups of customers.

4.4 Importance of

In today’s customer-dri
high-quality product at
the company that enters
captures the largest shar
this, one must simultan
and assembly during th
cost and improve prod
during the product de
solved in the very early
at a later stage is very s
a company decides to g
parts and testing them.
better than design A an
loses all the money an
decides to change the d
the market, then it incu
of the product could be
There is ample evidenc
traced to the design of
ness opportunities and market shares
nd benefits over and above a competitor’s product
et share
ers, continuous product improvements are made
ustomers, new features are added
atures that can be added to a product, but all such
porated because each feature costs money. Moreover,
ements are different and they are not willing to pay
efore, every supplier needs to supply a different mix
groups of customers. The following list will help the
ination of product features to meet customer’s need.
ncerns of customers.
into three categories: (1) must have, (2) important
to have.
on a scale of 1 to 10 and quantify the information.
o get a blend of features that will be best for various
Product Development
ven global marketplace, it is important to launch a
low cost with quick turn-around time. In general,
into the market first with a new high-quality product
e of the market and makes a greater profit. To achieve
eously consider the requirements of manufacturing
e product design phase in order to reduce product
uct quality. By employing concurrent engineering
velopment process, major design problems can be
stages of the design phase. The cost of design changes
ignificant compared to an earlier stage. For example,
o with design option A and starts making prototype
Once it finds out at this stage that design B will be
d tries to convert everything for design B, then it
d time spent thus far in design A. If the company
esign after the product is manufactured and reaches
rs additional costs for such design changes. A recall
for faulty design or a major drawback in the product.
e available in which fitness-for-use problems can be
the product. For example, in a study of seven space

programs, 35.2% of com
errors.

During a typica
rework dollars were tr
products of moderate co
the product developm
problems.

4.5 Concurrent En

Concurrent engineering
disciplines, such as desi
etc., during product d
becoming popular beca
ment cycle time and co
involves serial activities
packaging, service and
in Figure 4.1. In this app
without interacting wit
the part designed by the
be production efficient. F
tolerance for the outer d
manufacturing group.
rejects it because the pa
on the design and make
specify sharp corner, hi
that may not be produc
design with the manufa
rework and delay. Simil
department to ensure t
allocated for the produc

FIGURE 4.1

Serial approach to product de

Concept
Development
ponent failures were due to design or specification
l period of 11 months at a chemical plant, 42% of the
aced to research and development. For mechanical
mplexity, it is estimated that the errors made during
ent phase caused about 40% of the fitness-for-use
gineering
implies the simultaneous use of various engineering
gn, manufacturing, marketing, packaging, reliability,
evelopment activity. This branch of engineering is
use it has a significant effect on reducing develop-
st. The conventional way of developing a product
from various groups such as design, manufacturing,
maintainability, reliability, and marketing as shown
roach, the product design group designs the product
h manufacturing and/or other groups. Many times,
design team may not be manufacturable or may not
or example, the design group may specify a 0.002-in.
iameter of a pultruded part and then passes it to the
The manufacturing team looks up the design and
rt cannot be fabricated. The design team again works
s related changes. Similarly, the design engineer may
gh flatness, high surface
quality, and other features
tion feasible. Therefore, it is important to discuss the
cturing engineer early in the design phase to avoid
arly, design needs to be discussed with the packaging
hat the product size fits into the packaging space
t. This is critical in the automative industry. There is

Product
Design
Process
Design
Verification by
packaging, service,
and other disciplines
sign.

a significant space cons
sands of parts are assem
is increasing day by da
features and a compact
look at the design to ens
servicing. All these requ
several times, and som
scratch.
The current market d
in a concurrent enginee
greater need for strong
the design engineer bec
product design. It is req
of manufacturing, assem
right in the design pha
the lead time, and imp
work together is to avo
opment cycle. It is estim
a change in the product
design phase. Changin
changes in tool, mater
Therefore, there is grea
the early design stage b
There are many way
and performance require

FIGURE 4.2

Schematic diagram of concur
Marketing
and Sales
Reliab
Pack
traint in the design of an automobile, in which thou-
bled together in compact form. This space constraint
y because customers are asking for more and more
car for fuel efficiency. The service engineer should
ure that the various parts are easily accessible during
irements may force the designer to change the design
etimes to restart the entire design process from
emand is to perform product development activities
ring environment as shown in Figure 4.2. There is a
interaction between the manufacturing engineer and
ause manufacturing decisions are directly related to
uired to simultaneously consider the requirements
bly, packaging, service, distribution, and disposal
se to reduce the per-unit cost of production, reduce
rove quality. The reason various disciplines need to
id changes in the design late in the product devel-
ated that there is a tenfold increase in cost for making
ion phase as compared to changes made early in the
g the design in the production phase may result in
ial, equipment, planning, and labor requirements.
ter emphasis on moving the engineering changes to
y utilizing concurrent engineering.
rent engineering.
Product
Development Team
Process Design
ility
Serviceability
and
Maintainability
aging
Product
Design
s a product can be designed to meet the functional
ments of the application. Thus, early design decisions

have a significant effect
might select adhesive b
ical locking, or insert
process requires a diff
production cost process
other requirements, an i
operations. Clearly, the
significant impact on ov
and design for assembly
of design. Therefore, it i
early design phase to c
requirements of the va
changes during produc

4.6 Product Life C

Every product, depend
death. In general, produ
where market needs an
sional shape and size. In
the customer. For exam
the dust problem in th
sandpaper, in which th
ufacturing company, th
smaller scale, called the
low until the product s
critically affects the m
feedback to improve th
tance in the marketplac
the growth phase whe
recognition, and advert
its maturity phase whe
at a rate economy incr
competition due to the
continuous improveme
of the product. Addition
the product is divided
customer groups. After
of the introduction of a
using better technology
and composite boats r
decline phase, managem
by incorporating new t
on product life-cycle costs. For example, a designer
onding, mechanical fastening, snap fitting, mechan-
molding for the joining of two components. Each
erent production planning, equipment set-up, and
. Depending on the production rate, application, and
nformed decision is made to select the right assembly
ability to improve the quality of design will have a
erall product cost. Design for manufacturing (DFM)
(DFA) strategies can be used to improve the quality
s a good idea to invest more time and effort into the
ome up with a design that meets (or exceeds) the
rious disciplines. This will result in fewer or no
tion.
ycle
ing on its value and need, has a life from birth to
ct inception takes place in the product design phase,
d requirements are transformed into a three-dimen-
most cases, the idea for a new product comes from
ple, when customers complained to 3M Inc. about
eir sandpaper, 3M came up with the idea of wet
e dust problem is removed. After its birth in a man-
e product is introduced into the marketplace at a
test sample. During this stage, product sales remain
tarts to gain familiarity and acceptance. This phase
anagement to react on customer’s complaints and
e performance and its capabilities for greater accep-
e. After the introductory phase, product enters into
re product sales increase through word of mouth,
isement. After the growth phase, product enters into
re annual sales remain almost the same or increase
eases. During this phase, the product experiences
introduction of other similar products. In this phase,
nt is done to lower the cost and increase the quality
al features are added to the product and sometimes
into different groups to meet the need(s) of various
some period of time, product sales decline because
better product in the market to meet similar needs
. For example, composite golf shafts, fishing rods,
eplaced metal or wood counterparts. During this
ent may try to revive the product by innovation or
echnology.

Launching a new pro
time and money, along
barriers to product inn
development, advertise
As the demand and pr
decreases. The higher co
to compete with big com
place around the world
pete in the market.

4.7 Phases of Prod

The complete product
stages (or phases) for th
Each phase has its goal
phase is divided into se
different types of produ
PDP, some practice fou
The goal of each of the
costs, minimize lead tim
of a PDP are discussed

4.7.1 Concept Feasib

In this phase, market
performance requireme
team of experts from va
ing, materials, marketin
members are not only e
discipline of other team
and cultural barriers. T
dimensional product s
geometries, manufactur
is to create a preliminar
the technical feasibility
important element of th
to the company and to
products that compete w
prices are compared wi
the proposed product is
inary product and proc
(ROI) are reviewed, a g
duct onto the market costs a significant amount of
with market uncertainities; these are the biggest
ovation. The high cost of investment for research,
ment, and sampling increases the initial product cost.
oduction volume of the product increases, the cost
st of investment is a big barrier for small companies
panies. Business acquisitions and mergers are taking
to overcome this initial barrier to successfully com-
uct Development
development process (PDP) is divided into several
e successful design and fabrication of the product.
s and associated activities to meet those goals. Each
veral activities or tasks. Different industries practice
ct development processes. Some practice three-phase
r-phase PDP, and some practice seven-phase PDP.
se is to minimize potential errors, reduce product
e, and improve product quality. Six important phases
below.
ility Phase
need of a product with associated functional and
nts is identified. The ideas are then reviewed by a
rious departments such as engineering, manufactur-
g, sales, finance, and sometimes customers. The team
xperts in their areas but also knowledgeable in the
members. This helps avoid communication problems
he panel transforms customer needs into a three-
hape and size without much attention to specific
ing, or technical details. The purpose
of this phase
y design and production scenerios and then evaluate
of designing and manufacturing the product. The
is feasibility study is to estimate the expected cost
the customer. At this stage, a list of competitors’
ith the proposed product are identified. Competitor
th the expected cost of the product, and the need for
examined. Once studies of the market need, prelim-
ess designs, project cost, and return on investment
o/no-go decision is made regarding the project.

4.7.2 Detailed Design

This phase utilizes the i
to come up with multip
ment team (PDT) is form
ing, manufacturing, m
marketing, and purchas
engineering representat
of the product. Various
ing, servicing, and oth
sessions are conducted
The purpose of brain-st
nents design, joint desi
ufacturing process selec
is not allowed. Significa
phase to come up with
as DFM, DFA, finite e
analysis (FMEA) are us
Once there are many
design options are com
(Boothroyd and Dewhu
or for selecting the most
is made for the best d
written down. This info
It may be possible th
may be discarded. In t
choices, or the above pr

4.7.3 Prototype Deve

After the product desig
its functionality, perfor
material specifications d
prototype parts. Maki
investment in tools. To a
prototyping is used in s
assembly needs. Rapid
pensive way of makin
apparatus slices the thr
cross sections, and then
wax layer by layer from
Depending on the size
The resulting part prov
review. It can be used b
or by purchasing person
of rapid prototyping sy
Phase
nformation generated in the concept feasibilty phase
le concepts about the product. A product develop-
ed, consisting of experts from the design engineer-
aterials, testing, packaging, reliability, service,
ing disciplines. This team is led by a product design
ive. This team meets on a regular basis for the design
functional, performance, service condition, packag-
er requirements are listed. Several brain-storming
among team members for the design of the product.
orming is to generate as many ideas about compo-
gn, assembly methods, material selection, and man-
tion. In a brain-storming session, criticism of an idea
nt amounts of time and effort are dedicated in this
best ideas for the design of the product. Tools such
lement analysis (FEA), and failure mode effective
ed to generate the best ideas.
design options available for the product, the various
pared. Tools such as Pugh analysis, DFA software
rst, Inc.), etc. are used for narrowing down the choices
promising design. A complete drawing of the product
esign, and product and material specifications are
rmation is then used to make prototype parts.
at the design selected may need to be modified or
hat case, a new design is selected from narrowed
ocess is repeated again.
lopment and Testing Phase
n is complete, it is important to test the design for
mance, and other requirements. The product and
eveloped in the previous phase are used to develop
ng prototype parts sometimes involves extensive
void expensive tooling and other investments, rapid
ome cases to make sure the design meets fitness and
prototyping, such as stereolithography, is an inex-
g parts for visual inspection. A stereolithography
ee-dimensional CAD files (solid models) data into
constructs the pysical part by depositing plastics or
bottom to top until the desired part is completed.
of the part, a prototype can be made in a few hours.
ides a quick conceptual model for visualization and
y marketing personnel for demonstration purposes
nel for increasing the accuracy of bids. With the help
stems, flaws in the design can be determined early

in the product develop
and fabrication. Once th
parts are made using th
Following the fabrica
based tests are perform
tested, it is a good idea
mance and other require
and a major source of f
tested, it is sometimes
cause of failure. Comp
meet the component-ba
are tested for their desig
assembly is created and
The purpose of proto
the product; the effects
ature extreme exposure
product operation over
ing: function, fit, and for
but should be represen
parts should be made
selected for the full-sca
not possible. For examp
molding of SMC are avo
Prototype testing provi
feasibility, and is valua
before committing reso
provides guidelines and
type parts are shown a
their feedback on the d
customer concerns abou

4.7.4 Preproduction D

After the product has p
learned are listed. The e
ing production processe
tifying machine, tools, a
processes for interchan
house resources and pr
vs. in-house production
In this phase, the inte
engineering representat
ciency of the product by
the manufacturing engi
of machine, tools, fixtu
ment cycle before expensive investment in tooling
e part meets the dimensional requirement, prototype
e manufacturing process specified for the product.
tion of prototype parts, component- and assembly-
ed. Before all the components are assembled and
to first test the individual component for its perfor-
ments. By doing this, the cost of assembly is avoided
ailure is recognized. Once parts are assembled and
difficult to figure out which component is the real
onent-based tests avoid such confusion. After parts
sed requirement, then various joints and interfaces
n requirement. Once that is done, complete product
tested.
type testing is to determine the design capability of
of service conditions such as fluid exposure, temper-
, etc. on product performance, and the reliability of
time. This phase concerns the three F’s of engineer-
m. The units built in this phase may not be complete
tative of the actual product. Ideally, the prototype
using the equipment and manufacturing processes
le fabrication of the product, but sometimes this is
le, prototype parts made by SRIM or compression
ided because of higher tooling and equipment costs.
des a good indication of the technology and design
ble in determining the adequacy of design process
urces to subsequent stages. Prototype testing also
directions for future efforts. In some cases, proto-
nd demonstrated to potential customers to obtain
esign. It expedites the marketing effort and eases
t the product.
emonstration, or Pilot-Scale Production
assed the prototype and testing phase, the lessons
ffort in this phase focuses on defining and simplify-
s; cutting the cost of material and production; iden-
nd fixturing needed; standardizing the product and
geability with existing product line; evaluating in-
oduction facility; making decisions on outsourcing
; etc.
grated discipline team is led by the manufacturing
ive. This helps to document the manufacturing effi-
the most qualified person on the team. By keeping
neer as a leader of the team, fabrication knowledge
ring, material handling, process flow, process cost,

and product cost is uti
making sure that the pr
The next step is to de
the production rate req
ducing a small batch of
Quality and dimensiona
is made to specificatio
manufactured is tested
ground, or under actual
quality measurements,
back to rework.

4.7.5 Full-Scale Produ

After successful demons
for sale and distribution
mode of distribution, q
warehousing, and mark
formally introduced to
team transfers the produ
ments such as sales, adv

4.7.6 Continuous Imp

Once the product is on
from customers, sales,
may complain about he
a better operation for p
experience gained in m
design changes are mad
to eliminate field failure
changes can go through
development. The comp
lower the cost of produ
During the product d
to make sure that the go
section briefly describes

4.8 Design Review

Design review is an imp
In general, there are fou
lized.
The design engineer remains responsible for
oduct is in the product specification envelope.
mostrate the capability of the production process for
uirement, tolerance, and other requirements by pro-
products. This is also called pilot-scale production.
l inspections are performed to make sure the product
ns and is of the desired quality. The product thus
for service conditions in a test lab or in the proving
conditions. Based on the manufacturing experience,
and test results, the design is either released or sent
ction and Distribution
tration of pilot-scale production, the product is ready
. In this phase, the focus is on packaging decisions,
uality assurance procedures, order entry systems,
eting strategy. This is the phase when the product is
the market. In this phase, the product development
ct knowledge and its value to other company depart-
ertising, accounting, quality assurance, etc.
rovement
the market, the company begins to receive feedback
marketing, and other groups. The plant employees
alth and safety features of a process or might suggest
erforming various manufacturing steps. Based on
arketing, sales, production, and use of the product,
e to improve product quality and performance, and
s that were caused during product use. These design
one or more of the previous phases of the product
any continuously strives to improve the quality and
ct to make it fit for competition.
evelopment process, various design reviews are set
als and objectives of the PDP are met. The following
the design review process.
ortant element in the product development activity.
r to six design reviews such as preliminary design

review (PDR), interim
and final design review
reviews are held at dif
make sure the activity
conducted by the leader
departments (e.g., man
materials) who are expe
not directly associated
are highly experienced
project. The specialists
tomer or a university
developmental work p
members examine the
The purpose of the revie
problems with the desig
of action to meet the ob
product will function s
for experts to ask critic
cessful design review
product and process de
problems and challenge
Design review is a fo
The PDT leader sched
meeting. Minutes of the
and PDT members. Co
PDT meetings.

4.9 Failure Modes

FMEA is performed du
product can experience
consequences of those
the total system. It prov
causes and effects of fail
is to redesign the prod
addresses the causes a
mode, effects on total s
rence are examined. Th
safety, and durabilty. Th
FMEA can be applied
FMEA should be inco
FMEA helps the produc
design review (IDR), critical design review (CDR),
(FDR) in a product development cycle. These design
ferent phases of the product development cycle to
is going in the right direction. The design review is
of the PDT and attended by managers from various
ufacturing, application, marketing, purchasing, and
rts in the company’s product lines and business, and
with the development of a design. These specialists
professionals and are aware of the objectives of the
can come from outside the company, such as a cus-
professor. The PDT leader presents the results of
erformed up to that point in time, and committee
results and provide future direction for the project.
w is to get new ideas for the design, correct potential
n, screen design choices, and provide future courses
jectives of the project. The review ensures that the
uccessfully during use. It provides an opportunity
al questions about the product and process. A suc-
not only provides constructive criticism about the
sign, but also provides solutions to various design
s.
rmal activity, typically completed in a few hours.
ules a meeting date and sends the agenda for the
meeting are taken and circulated among committee
urses of action are noted and followed during the
and Effects Analysis (FMEA)
ring PDP to determine the potential failure modes a
during operation and to evaluate the effect and
failure modes on the functions and performance of
ides a systematic method for analyzing the potential
ure before design is finalized. The aim of this analysis
uct for maximum reliability. FMEA identifies and
nd mechanisms of failure modes. For each failure
ystem, its seriousness, and its probability of occur-
e purpose of FMEA is to improve quality, reliability,
e net effect of this is to reduce product life-cycle cost.
during product design as well as process design.
rporated during product development activities.
t development process by the following means:

• It establishes a li
PDT goes throug
ing plan to avoi
product improve
• It ranks the failu
system. PDT de
improvements ac
• It provides futur
lishes guidelines
• It serves as a too
alternatives.
In performing the FM
1. What are the fun
2. How can the asse
fail?
3. What are the pro
4. What are the cau
5. What are the eff
performance of t
6. How can these fa
7. How will the fai
8. How can failure
9. What are the des
10. If failure takes pl
to reduce its sev
Failure is the loss of
predetermined manner
noisy, or unable to do a
ment. Failure modes are
modes in a product in
failure, etc. For each fail
It is very important to i
known, the solution bec
provides corrective acti
To perform FMEA, th
is divided into sub-asse
components. The functi
are determined and rela
failure modes caused b
each component and its
st of potential failure modes in the product. The
h the list and develops a design and manufactur-
d these failure modes. Thus, the quality of the
s significantly.
re modes according to their effects on the overall
velops priority lists and test plans for design
cording to failure mode rankings.
e reference for analyzing field failures and estab-
for design changes.
l in the selection of process and product design
EA, one should ask the following questions:
ctions of the product or assembly?
mbly, sub-assemblies, and individual components
babilities of those failures and their severity?
ses of failure?
ects of each failure mode on the functions and
he product?
ilures be prioritized?
lure be detected?
be avoided?
ign options to eliminate failure?
ace, then what corrective actions should be taken
erity?
function or ability to perform a prescribed task in a
. Examples of failures include a product becoming
task, or not meeting desired performance require-
those that cause the failure to occur. Typical failure
clude part broken, loose, tight, bent, leakage, joint
ure mode, there are several possible causes of failure.
dentify the real cause of a failure. Once the cause is
omes very evident in many cases. Knowing the cause
on and design solutions.
e product is divided into assemblies. Each assembly
mblies and then the sub-assemblies are divided into
ons of each assembly, sub-assembly, and component
tionships among each other are established. Potential
y operation and service conditions are evaluated for
effect on the next higher item or on the total system

is analyzed. The reliabi
about their design, and
to reduce the effect of f
group has a record of th
from the company’s pa

Reference

1. Juran, J.M. and Gry

Bibiliography

1. Boothroyd, G., Poli,

New York, 1982.
2. Gryna, F.M. and Jur

opment Through Use,

Questions

1. How can the ma
developing a ma
2. Why is it importa
ing with the des
stage?
3. What are the ben
4. What are the im
phase?
5. What is FMEA? H
design?
6. Why is it necess
approach when m
lity group poses possible failure modes to the PDT
PDT takes corrective actions or preventive measures
ailure or totally eliminate the failure. The reliability
e probability of a certain type
of failure in a product
st experience.
na, F.M., Eds., Juran’s Quality Control Handbook, 1970.
C.R., and Murch, L.E., Automatic Assembly, Marcel Dekker,
an, J.M., Quality Planning and Analysis: From Product Devel-
McGraw-Hill, New York, 1993.
nufacturing engineer assist the design engineer in
nufacturable product?
nt for the manufacturing engineer to begin work-
ign team very early in the product development
efits of concurrent engineering?
portant elements of the product development
ow does it help in coming up with better product
ary to follow a systematic product development
aking a product?

Design for Ma

5.1 Introduction

Companies are constant
faster, and cheaper. Com
can they afford a length
no longer be viewed i
engineering concept to
make it. The design en
together to come up w
fabricating the products
turing engineers work se
of automobiles, the man
box-like product that is
it. On the other hand, t
is creative, eye-catching
but it would be unaffor
To be competitive, the
of time, with minimum
several philosophies, su
design for quality, desi
developed. The primar
manufacturing, assemb

cess. This is achieved b
environment to avoid l
A product can be desi
and other requirement
different design concep
for an application depen
well as the knowledge a
design solutions to a pr
design is the best soluti
that may be better than
nufacturing
ly being challenged to find means to do things better,
panies can no longer overdesign the product, nor
y product development cycle time. The products can
ndividually, and designers can no longer pass the
the manufacturing engineer for finding the ways to
gineer and manufacturing engineer need to work
ith a best design and manufacturing solutions for
cost-effectively. For example, if design and manufac-
parately to create the design of the outer body panels
ufacturing engineer will come up with a flat or square
cheaper and quicker to make, but no one would buy
he design engineer will come up with a design that
, and satisfies all customer needs and requirements,
dable. In either case, the product will not sell.
product needs to be designed in a minimum amount
resources and costs. To meet current market needs,
ch as design for manufacturing, design for assembly,
gn for life cycle, and concurrent design, are being
y aim of these philosophies is to think about the
ly, quality, or life-cycle needs during the design pro-
y working concurrently in a concurrent engineering
ater changes in the design.
gned in many ways to meet functional, performance,
s. Therefore, different organizations come up with
ts to meet the same application needs. The solution
ds on how the problem is defined to the designer as
nd creativity of the designer. Because there are many
oblem, the question arises as to how to know which
on. It is also possible that there may be other designs
the realm of the designer. Design for manufacture is

a tool that guides the d
then provides the optim
approval, and concept im
the design of a part to
manufacturing method.
engineer should have a
various composite manu
be familiar with tools s
assembly (DFA), etc. fo
metals, composite mate
part integration, and the
Engineers utilizing is
tionally fabricate parts
book based on performa
the manufacturing proc
is not viable in the field
materials, the material
merge into a continuum
ture in an integrated f
winding, pultrusion, R
damping, and mass cha
tions and fiber volume f
distinct microstructural
The best design exam
grown in the entire syst
various parts and assem
logical manufacturing
innovation by learning
world.

Designs in nat
compliant. Nature tries
traditionally make the
Kota

1,2

developed a on
the conventional steel s
nisms are single-piece, fl
undergoing elastic defo

5.2 Design Proble

The defect or quality pr
design, bad material, an
product is correctly des
rectly designed, then th
esigner in coming up with better design choices and
um design. It is a tool for concept generation, concept
provement. It integrates processing knowledge into
obtain maximum benefits and capabilities of the
To come up with the best design, the manufacturing
good knowledge of the benefits and limitations of
facturing techniques. The team members should also
uch as design for manufacturing (DFM), design for
r developing high-quality design. As compared to
rials offer the highest potential of utilizing DFM and
refore can significantly reduce the cost of production.
otropic materials such as aluminum and steel tradi-
by first selecting raw materials from a design hand-
nce requirements. Once the raw material is selected,
ess to fabricate the part is identified. This philosophy
of composite materials. With engineered composite
selection, design, and manufacturing processes all
philosophy embodying both design and manufac-
ashion. For example, a rod produced by filament
TM, or braiding would impart distinct stiffness,
racteristics due to different fiber and resin distribu-
ractions. Composites manufacturing processes create
properties in the product.
ple is Nature’s design in which different artifacts are
em as a single entity. In contrast, engineers fabricate
ble them together. At present, we do not have bio-
processes but we have plenty of opportunities for
and imitating the no-assembly designs of the natural
ure are strong but not necessarily stiff — they are
to make the design compliant, whereas engineers
structure and mechanism stiff. Ananthasuresh and
e-component plastic stapler in which they replaced
tapler with no-assembly design. Compliant mecha-
exible structures that deliver the desired motion by
rmation as opposed to rigid body motion.
ms
oblem in the product is caused by three things: bad
d wrong manufacturing process. For example, if the
igned, and if the manufacturing method is not cor-
e product will be defective. Similarly, an incorrectly

designed product will a
the right materials and
these defects is caused
A poor design can cau
increases the cost of the
design problems includ
missing parts, labor-in
difficult to manufacture
quality, ergonomic prob
lems can be solved ear
quality results in a high
cost. Product quality de

5.3 What Is DFM?

DFM (design for manu
products, keeping manu
of paper and identifyi
requirements. It utilizes
the part. Best practices f
number of parts, create
tions, and create ease of
ments with the lowest-c
In the past, several p
designers were not awa
on the market, nor the
result, products were he
ations, and resulted in p
the product, manufactu
uct design. The designe
In general, the real chal
a good understanding
of processing and mate
• Narrow design c
• Perform concep
improvement
• Minimize produ
• Achieve high pro
• Simplify product
• Increase the com
lso result in quality problems despite having chosen
good manufacturing methods. The occurrence of
by several factors inherent in the design.
se many problems in production plants. It not only
product, but also decreases product quality. Common
e loose parts, rattling, parts not aligned, tight parts,
tensive assembly, too many machining operations,
, difficult to assemble and bond, difficult to achieve
lems, serviceability problems, etc. These design prob-
ly in the design phase utilizing best practices. Poor
er rejection rate and therefore a higher production
pends on how the product is designed.
facturing) can be defined as a practice for designing
facturing in mind. DFM starts by taking a plain sheet
ng a product’s functional, performance, and other
rules of thumb, best practices, and heuristics to design
or a high-quality
product design are to minimize the
multifunctionality in the part, minimize part varia-
handling. DFM involves meeting the end-use require-
ost design, material, and process combinations.
roduct problems arose because of poor design. The
re of the various manufacturing techniques available
capabilities of each manufacturing technique. As a
avy, had many parts and thus many assembly oper-
oor quality and increased cost. To effectively design
ring knowledge needs to be incorporated into prod-
r should know how the process and design interact.
lenge in designing composite products is to develop
not only of engineering design techniques, but also
rial information. The purpose of DFM is to:
hoices to optimum design (Figure 5.1)
t generation, concept selection, and concept
ct development cycle time and cost
duct quality and reliability
ion methods
petitiveness of the company

• Have a quick an
production phas
• Minimize the nu
• Eliminate, simpl

5.4 DFM Impleme

The main objective of D
content in the produc
requirements. DFM can
production or on the m
product more cost-comp
to products made of co

5.4.1 Minimize Part C

There is good potential
arate parts. At General M
DFM strategies have red
many product lines. Co
gration. Minimization of
the need for assembly, i
and servicing. Accordin

of one.” In general, mor
requirement, a differen
requirement, or an adju
is the steel identification
replaced by a single in
monocoque composite
design becomes overly

FIGURE 5.1

Design flow diagram in DFM
D
Problem Definition
(Functional
performance and
other requirements)
d smooth transition from the design phase to the
e
mber of parts and assembly time
ify, and standardize whenever possible
ntation Guidelines
FM is to minimize the manufacturing information
t without sacrificing functional and performance
also be applied for a product that is already in
arket. The main objective here will be to make the
etitive. The following DFM guidelines are applicable
mposites, metals, and plastics.
ounts
for part integration by questioning the need for sep-
otors, Ford, Chrysler, GE, IBM, and other companies,
uced the total number of part counts by 30 to 60% in
mposite materials offer good potential for part inte-
part counts can result in huge savings by eliminating
nventory control, storage, inspection, transportation,
g to Huthwaite,3 “the ideal product has a part count
e than one part is needed if there is a relative motion
t materials requirement, a different manufacturing
stment requirement. An example of part integration
badge clip that has four different parts but can be
jection molded plastic part. Another example is the
.
1. Narrow design
choices and
incorporate
manufacturing
knowledge
2. Select concept and
improve
DFM
High-Quality
Design
esign Choices
1. Design A
2. Design B
3. Design C
4. Design D
5. Design E
bicycle frame. Do not perform part intergration if
complex, heavy, or difficult to manufacture.

A typical automobile
parts to meet various
Heloval 43-meter luxur
9000 metallic parts for h
of parts for outfitting.
To determine if a part
questions should be ask
1. Do the parts mo
2. Is there any need
3. Will the part req
4. Will there be a n
If the answers to the a
candidate for replaceme
the number of parts.
• Question and ju
questions above;
uct by eliminatin
• Create multifunc
• Eliminate any pr
customer.
• Use a modular d

5.4.2 Eliminate Threa

Avoid the use of screws
estimated that driving
the cost of a screw. The
complexity in assembly
variation, to join two c
teners creates the poten
has used this philosoph
and replacing them wi
less parts and 70% redu
Snap-fits are used wit
ease of assembly due to
concerns regarding the
clamp load, etc.

5.4.3 Minimize Variat

Part dimensional variati
of product defects and n
, airplane, or luxury yacht consists of thousands of
functional or performance needs. For example, a
y yacht from CMN Shipyards is comprised of about
ull and superstructure and over 5000 different types
is a potential candidate for elimination, the following
ed:
ve relative to each other?
to make parts using a different material?
uire removal for servicing or repair?
eed for adjustment?
bove questions are “no,” then the part is a potential
nt. The following guidelines can be used to minimize
stify the need for a separate part. Ask the four
and if the answer is “no,” then redesign the prod-
g the separate part.
tionality features in the part.
oduct feature that does not add any value for the
esign.
ded Fasteners
, nuts, bolts, and other fasteners in the product. It is
a screw into the product costs almost 6 to 10 times
use of fasteners increases inventory costs and add
. Fasteners are used to compensate for dimensional
omponents, or for part disassembly. The use of fas-
tial for a part to become loose during service. IBM
y to redesign its printer, eliminating many screws
th snap-fit assembly. The resulting design had 60%
ced assembly time.
h plastics or short fiber composite parts and provide
the lack of any installation tool requirement. General
use of snap-fits include strength, size, servicing,
ions
on as well as property variation are the major sources
onconformities. Try to use standard parts off-the-shelf

and avoid the use of sp
bushings or O-rings, sea
size would mean the sam
aims to reduce part cate
thus providing better in

5.4.4 Easy Serviceabi

Design the product such
The part should be visib
adjacent members for sc

5.4.5 Minimize Assem

For product assembly,
product, think about the
ments. It is preferable t

allows gravity to aid in
imizes part movement
It is better in terms of a

5.4.6 Provide Easy In

When there are more th
be brought close by per
easy insertion and align
• Provide generou
assembly.
• Provide self-loca
• Avoid hindrance
• Avoid excessive
• Design parts to m
• Avoid restricted

5.4.7 Consider Ease f

In an assembly plant, va
bly station. Workers pic
bonding or mechanical
parts such as springs, c
locked. It disrupts the
worker. For smooth ass
not be heavy and shoul
ecial parts. Eliminate part variations such as types of
ls, screws, or nuts used in one application. The same
e tool for assembly and disassembly. This guideline
gories and the number of variations in each category,
ventory control and part interchangeability.
lity and Maintainability
that it is easy to access for assembly and disassembly.
le for inspection and have sufficient clearance between
heduled maintenance using wrench, spanner, etc.
bly Directions
minimize assembly direction. While designing the
assembly operations needed for various part attach-
o use one direction; z-direction assembly operation
assembly. A one-direction assembly operation min-
as well as the need for a separate assembly station.
n ergonomics point of view as well.
sertion and Alignment
an two parts in a product, the mating parts need to
forming insertion or alignment. Some guidelines for
ment are:
s tapers, chamfers, and radii for easy insertion and
ting and self-aligning features where possible.
and obstruction for accessing mating parts.
force for part alignment.
aintain location.
vision for part insertion or alignment.
or Handling
rious parts are kept in separate boxes near the assem-
k up those parts and assemble them using adhesive
fastening or by slip-fit or interference-fit. Avoid using
lips, etc., which are easy to nest and become inter-
assembly operation and creates irritation for the
embly operation and ease
of handling, parts should
d not have many curves, thus reducing the potential

for entanglement. To av
locations should be eas
handling and aid in ori
desired location. The fol
suggestions are more ap
• Minimize handli
sharp corners or
• Keep parts withi
• Avoid situations
get the part.
• Minimize operat
two hands or ad
• Avoid using part
• Use gravity as an

5.4.8 Design for Mul

Once an overall idea of
individual components
preferable to use mold
shape parts. For exampl
the structural requireme
ment, self-locating, mo
helps minimize the num

5.4.9 Design for Ease

In composite part fabric
out knowledge of the m
cess has its strengths an
to reap the benefits of
close tolerances are requ
winding is preferred co
be simplified as much
assembly and thus in co
the products can easily

5.4.10 Prefer Modula

A module is a self-cont
standard interface for co
ple, a product that has 1
oid physical fatigue of the worker, part and assembly
y to access. Parts should be symmetric to minimize
enting. Add features that help guide the part to its
lowing suggestions can improve part handling. These
plicable for a high-volume production environment.
ng of parts that are sticky, slippery, fragile, or have
edges.
n operator reach.
in which the operator must bend, lift, or walk to
or movements to get the part. Avoid the need for
ditional help to get the part.
s that are easy to nest or entangle.
aid for part handling.
tifunctionality
the product’s functions is gleaned, one can design
such that they provide maximum functionality. It is
ing operations that provide net-shape or near-net-
e, an injection molded composite housing part meets
nt of the product and has built-in features for align-
unting, and a bushing mechanism. This technique
ber of parts.
of Fabrication
ation, product design cannot be made effective with-
anufacturing operations. Each manufacturing pro-
d weaknesses. The product design should be tailored
the selected manufacturing process. For example, if
ired on the inside diameter of a tube, then filament
mpared to a pultrusion process. The design should
as possible because it helps in manufacturing and
st savings. Workers and others who are dealing with
understand simplified design.
r Design
ained component that is built separately and has a
nnection with other product components. For exam-
00 parts can be designed to have four or five modules.

Each module can be ind
the design of the other m
in the final assembly, a
be easily replaced by a
space, automotive, com
systems, bumper beams
produced, and improve
in the vehicle. In each
which are again design

5.5 Success Stories

There are many examp
number of parts and r
bicycle frame is one exa
composite monocoque
have reduced total part
some of the success stor
quality and lowering th

5.5.1 Composite Pick

Ford, in partnership wit
oped a composite picku
pickup box is close to 2
required 45 pieces of she
piece box, there are fewe
it takes up less floor spa
Using a composite in
weight, resulting in in
composite (SMC) box in
inating the risk of rust
The composite box ex
ified by Ford Truck for
superior to steel for cor
posite box reduce weig
cut down on productio

5.5.2 Laser Printer

A laser printer has hun
functionality. IBM, GE, a
ependently designed and improved without affecting
odules. Modular design is preferred because it helps
s well as in servicing where a defective module can
new module. Modular design can be found in aero-
puter, and other products. For example, steering
, and chassis systems are separate modules designed,
d upon by independent organizations and assembled
of these modules, there are many other modules,
ed by various groups of the organization.
les for which DFM techniques have minimized the
educed assembly time. The monocoque composite
mple where several metal parts are replaced by one
structure. In automotive applications, SMC parts
counts by integration of various parts. Following are
ies of DFM, where it helped in improving the product
e product cost.
up Box
h The Budd Company’s Plastics Division, has devel-
p box for the Ford 2001 Explorer SportTrac. The SMC
0% lighter than a typical steel box. The old process
et metal to be assembled. With the new composite one-
r pieces, fewer tools, and fewer assembly fixtures, and
ce in the assembly plant, which results in cost savings.
stead of steel yields an overall reduction in vehicle
creased fuel economy. A structural sheet molding
ner does not trap water under a liner, thereby elim-
damage to the pickup bed.
ceeds the 150,000-mile durability requirements spec-
all pickup boxes. It is built “Ford Tough’’ and is far
rosion and dent resistance. Not only does the com-
ht, improve fuel economy, increase durability, and
n time and cost, but it is also recyclable.
dreds of parts and is assembled to meet the desired
nd other companies have tried to reduce the number

of parts in laser printers
laser printer, the latest m
ington, KY), GE Plastic
using injection molded
for the sheet metal chas
oxide (PPO) design. Th
imization of number of
50% reduction in assemb

5.5.3 Black & Decker

Black & Decker has us
components purchased

ers was reduced from 4
future products. Simila
266 to 12 (one seal, one

5.6 When to Apply

DFM should be employ
process when decisions
there is the best chance
after the product design
changes in the design at
DFM can also be used t
cost benefits and increa
with a final design in m
techniques.

5.7 Design Evalua

An application has man
meet those requirement
and requirements that a
compare the various de
analysis and other techn
Here is a method that c
method, a matrix is crea
as shown in Table 5.1.
using DFM and DFA tools. In the new Optra S 1250
odel manufactured by Lexmark International (Lex-
s (Pittsfield, MA) redesigned the chassis component
parts. GE Plastics reduced the part count from 189
sis to a 12-part fiberglass-reinforced polyphenylene
e design guidelines used were part integration, min-
parts, design for assembly, etc. The result: more than
ly time and more than 20% savings in assembly cost.
Products
ed DFM to greatly reduce the number of hardware
by the company.4 For example, the list of plain wash-
48 to 7 (one material, one finish, one thickness) in
rly, the number of ball bearings was reduced from
lubricant, one clearance, metric only).
DFM
ed in the early stages of the product development
have the greatest impact on product cost and when
for its implementation. It is too late to utilize DFM
is released or when the part is in production. Any
a later stage significantly increase the cost of product.
o improve the design of existing products to obtain
se market competitiveness. DFM helps in coming up
uch less time than with traditional product design
tion Method
y requirements, as well as many design options to
s. Each design option must be evaluated for features
re important to customers. It is a challenging task to
sign options, but selection processes such as Pugh
iques can simplify the task of selecting a best design.
an be used for concept selection. According to this
ted between criteria of selection and design options
Each design option is rated on a scale of 1 to 5 for

various selection criteri
its importance for that a
totaled for final selectio
selected as the best des

5.8 Design for Ass

It is found that the co
product costs in a wide

great need to lower the
of parts and by using s
The design for assembly
operation at minimum
between DFA and DFM
whereas DFM deals wit
comes under the envelo
the designer should ha
operations and should
parts reduces assembly
section of an automated
by Boothroyd and Dew

Assembly

In the early stages of
type of assembly metho
revolves around the cap

TABLE 5.1

Evaluation of De

Factors

Weight
Cost
Performance
Reliability
Noise
Assembly time
Robustness
Number of parts
Aesthetics
Ease of servicing

Total
a. The weight assigned to each criterion depends on
pplication. Each rating is multiplied by weight and
n. The design that obtains the highest point total is
ign.
embly (DFA)
st of assembly accounts for 40 to 50% of the total
variety of industrial products.5 Therefore, there is a
cost of assembly operations by reducing the number
imple assembly operations for the remaining parts.
(DFA) strategy is employed to design the assembly
cost and maximum productivity. The difference
is that DFA deals only with the assembly operation,
h the entire manufacturing process. Therefore, DFA
pe of DFM. To obtain maximum benefit from DFA,
ve a good understanding of the various assembly
justify the need for separate parts. Elimination of
time and cost, and can sometimes eliminate an entire
assembly machine. The DFA method was developed
hurst and is described in detail in Product Design for
the design phase, the designer should decide which
d is going to be best for the product. The design then
sign Concepts
Weight
(%) Design “A” Design “B” Design “C”
15 3 4 3
20 4 5 3
10 3 4 3
5 2 4 3
5 3 3 4
15 3 5 3
7 3 4 3
10 2 4 3
5 2 4 4
8 2 5 3
100 2.92 4.38 3.1
ability and benefits of the selected assembly method.

The decision on the as
parts in the product, pro
of the product is only 1
an annual production v
mation equipment wou
Boothroyd developed
presented a best way of
minimum actions. The s
ious design alternative
assembly sequence. Eve
sequences that different
nique, each assembly s
then be selected.
DFA guidelines for re
gration, unless there ar
for no assembly (DFNA
consolidated into mono
mechanisms, provided

5.8.1 Benefits of DFA

The objective of DFA i
avoid problems due to
results in the following
• Reduced numbe
• Reduced assemb
• Reduced assemb
• Ergonomically so
• Reduced produc
• Reduced produc
• Reduced capital
• Fewer design rel
• Weight saving
• Better inventory
• Better quality

5.8.2 Assembly-Relate

There are many defect
aware of these defects,
Common defects includ
sembly method is based on costs, total number of
duction rate, etc. For example, if the annual volume
000, then manual assembly should be preferred. For
olume of several million products, selection of auto-
ld be a better choice.
software for analyzing the assembly operation and
assembling parts for minimum part movements and
oftware determines assembly time and cost for var-
s, and helps in selecting an optimum design and
n for the same design, there are various ways and
parts can be assembled. Using the Boothroyd tech-
equence can be analyzed and a best sequence can
ducing the part count include promoting part inte-
e relative motion and other requirements. In design
), parts with relative motion between them can be
lithic mechanical devices using jointless compliant
the relative motion is small (e.g., in a stapler).
s to design the product for minimum assembly to
wear, lubrication, backlash, noise, and leakage. DFA
benefits:
rs of parts
ly operations and part complexities
ly time and cost
und design
t cost
t development time
investment
eases
control
d Defects
s caused by assembly operations. After becoming
solutions to reduce these defects can be determined.
e:

1. Part misaligned
2. Part damaged
3. Fastener-related
4. Missing parts
5. Part interchange
6. Part interference
In addition to the abo
defects. Rook

observed
turing operations are ty
errors themselves cause
error is primarily cause
• Forgetting to per
• Performing actio
tion, incorrect sc
• Misinterpretation
Other types of errors id

• Processing errors
• Errors caused du
• Misoperation or
• Working on wro
• Missing processi
The product-, process
Figure 5.2. The mistake
effects of the above er
(1000 ppm). Automotiv
ufacturers, etc. make th
actions and assembly o
in such cases becomes s
to the customer and cau
majority of product def

error-proofing of produ
involves designing the p

cannot

perform a mist
alarm as a reminder for
and the addition of feat
process for omission of
In the aerospace indu
to make the composite p
defects
d
s such as loose or tight part
ve defects, human errors are also a cause of assembly
that for 1 in 10,000 to 1 in 100,000 cases, manufac-
pically omitted without detection. That is, omission
defect rates in the range of 10 to 100 ppm. Human
d by:
form prescribed actions, resulting in missing parts
ns that are prohibited, such as incorrect lubrica-
rew, incorrect material, or incorrect part selection
of manufacturing step
entified by Poka-yoke7 are:
, such as overcooked or undercooked
ring setting up of fixtures, tools, and workpiece
adjustment mistakes
ng workpiece
ng operations
-, design-, and material-related defects are listed in
s described above rarely happen but the collective
rors typically exceed one mistake per 1000 actions
e manufacturers and suppliers, sporting goods man-
ousands of parts per day and go through millions of
perations per day. The total number of part defects
ignificantly high. Many times, the defective part goes
ses a serious problem. Studies have shown that the
ects are caused by mistakes.8,9 To avoid such errors,
ct and process designs is performed. Error-proofing
roduct or process such that an operator or a machine
ake. Error-proofing operations include placing an
missing operation, keeping a checklist of operation
ures for reminders, and redesigning the product and
the assembly operation.
stry, many prepreg layers are laid at various angles
art. Omission of a prepreg layer or incorrect placement

of a prepreg layer coul
parts. To minimize such
the quality control depa
as prescribed in the pro

5.8.3 Guidelines for M

To avoid mistakes durin
keeping the worker in th
• Simplifying the p
• Minimizing part
• Reducing assemb
• Maximizing equ
• Eliminating ergo
• Error-proofing th
The workplace and th
rials, fasteners, and par
that parts fall into their d
design the workplace,
error-proofing should b
little or no fatigue is giv

FIGURE 5.2

Typical product defects.
Process-Related
Defects
1. Residual stress
2. Warpage
3. Shrinkage
4. Improper fiber
distribution
5. Process incompatible
6. Inability to meet
tolerance and other
specifications
d significantly affect the performance of composite
errors in a prepreg lay-up process, personnel from
rtment check the lay-up sequence at certain intervals,
cess sheet.
inimizing Assembly Defects
g assembly operations, the parts should be designed
e mind. Workplace productivity can be enhanced by:
roduct design
s handling
ly operations and time
ipment uptime
stressors
e design and process
e machines should be designed such that the mate-
ts are as close as possible to a machine operator and
esired locations with little or no effort. To effectively
factors such as material handling, ergonomics, and
Product-Related Defects
1. Damaged parts
2. Part misalignment
3. Part loose or tight
4. Does not meet performance specs
5. Part missing
6. Nonconformity
7. Not to design specifications
Design-Related Defects
1. Difficult
to manufacture
2. Difficult to assemble
3. Tight tolerance
4. Difficult to service
5. Wrong process and
assembly selection
Material Properties-
Related Defects
1. Not to spec
2. Does not meet
performance
3. Moisture absorption
4. Fiber resin distribution
e given proper consideration. An action that causes
en top priority.

References

1. Ananthasuresh, G.K

Mech. Eng.,

p. 93, N
2. Kota, S., Synthesis o
assembly, submitted

3. Huthwaite, B., Des

Engineering, Roches
4. Bradyhouse, R., The
producible: Are the

neous Engineering Co

Dearborn, MI.
5. Boothroyd, G. and D

Dewhurst, Inc., Wak
6. Rook, L.W., Jr., Red
Sandia National Lab
7. Poka-yoke, Improvi
Shimbun, Ed.,

Facto

ductivity Press, Inc.
8. Hinckley, C.M. and
in producing non-co

9. Hinckley, C.M., A Gl
for Minimizing Defe
tion submitted to th
versity, Stanford, CA

Questions

1. Why is the know
2. Why is DFM mo
turing?
3. What are the com
4. In what ways doe
5. What is the diffe
6. In an ideal produ
7. How would you
for elimination?
8. What are the com
9. What are the com
. and Kota, S., Designing compliant mechanisms, ASME
ovember 1995.
f mechanically compliant artifacts: product design for no
to ICED.
ign for competitiveness, Bart Huthwaite Workshops, Troy
ter, MI, 1988.
rush for new products versus quality designs that are
se objectives compatible?, presented at the SME Simulta-
nference, June 1, 1987, Society of Manufacturing Engineers,
ewhurst, P., Product Design for Assembly, Boothroyd and
efield, RI, 1987.
uction of Human Error in Production, SCTM 93-62 (14),
oratories, Division 1443, June 1962.
ng product quality by preventing defects, Nikkan Kogyo
ry Magazine, English translation copyright © 1988 by Pro-
Barkan, P., The role of variation mistakes and complexity
nformities, J. Qual. Technol., 27(3), 242, 1995.
obal Conformance Quality Model — A New Strategic Tool
cts Caused by Variation, Error, and Complexity, disserta-
e Department of Mechanical Engineering, Stanford Uni-
, 1993.
ledge of DFM important in product design?
re important in the area of composites manufac-
mon design problems?
s the minimization of part counts help a company?
rence between DFM and DFA?
ct, how many parts should there be and why?
determine whether a part is a potential candidate
mon process-related defects?
mon assembly-related defects?

Manufacturin

6.1 Introduction

Every material possesse
acteristics and therefore
to transform the materi
be best suited for one m
material. For example, w
ing is quite heavily uti
shape. Ceramic parts ar
from powder using hot
or sheet to the desired s
In metals, standard size
welded or fastened to
standard-sized sheets o
cuts the fibers and crea
tinuous fibers decrease
ease of composites pro
Composites do not hav
part processing as comp
roll forming, or casting
formed to near-net-shap
applications such as ma
temperature with little
cessing of composites a
ties for transforming th
There are two major
First, it minimizes the m
ing. Second, it minimize
are cases when machini
create special features.
approach than machini
g Techniques
s unique physical, mechanical, and processing char-
a suitable manufacturing technique must be utilized
al to the final shape. One transforming method may
aterial and may not be an effective choice for another
ood is very easy to machine and therefore machin-
lized for transforming a wooden block to its final
e difficult to machine and therefore are usually made
press techniques. In metals, machining of the blank
hape using a lathe or CNC machine is very common.
s of blanks, rods, and sheets are machined and then
obtain the final part. In composites, machining of
r blanks is not common and is avoided because it
tes discontinuity in the fibers. Exposed and discon-
the performance of the composites. Moreover, the
cessing facilitates obtaining near-net-shape parts.
e high pressure and temperature requirements for
ared to the processing of metal parts using extrusion,
. Because of this, composite parts are easily trans-
e parts using simple and low-cost tooling. In certain
king boat hulls, composite parts are made at room
pressure. This lower-energy requirement in the pro-
s compared to metals offers various new opportuni-
e raw material to near-net-shape parts.
benefits in producing near-net- or net-shape parts.
achining requirement and thus the cost of machin-
s the scrap and thus provides material savings. There
ng of the composites is required to make holes or to
The machining of composites requires a different
ng of metals; this is discussed in Chapter 10.

Composite productio
materials, including fibe
pounds, for the fabrica
nique requires differen
conditions, and differen
shows a list of the vario
ufacturing techniques a
materials used in those
own advantages and d
shapes, part cost, etc. P
of a manufacturing tec
parameters. The main
commercially available
and thermoplastic-base
turing techniques are d
methods of applying h
other important param
help in selecting the r
describes the manufactu

6.2 Manufacturing

It is a monumental cha
select the right manufac
being that design and
terms of raw materials
section briefly discusse
process depends on the
depend on the product
ments of the part, as de

6.2.1 Production Rate

Depending on the appl
different. For example, t
tion, for example, 10,00
(20,000 per day). In the
ally in the range of 10 to
facturing techniques th
production environmen
cannot be used for high
(SMC) and injection mol
n techniques utilize various types of composite raw
rs, resins, mats, fabrics, prepregs, and molding com-
tion of composite parts. Each manufacturing tech-
t types of material systems, different processing
t tools for part fabrication. Figure 1.5 in Chapter 1
us types of most commonly used composites man-
nd Figure 2.1 in Chapter 2 shows the type of raw
manufacturing techniques. Each technique has its
isadvantages in terms of processing, part size, part
art production success relies on the correct selection
hnique as well as judicious selection of processing
focus of this chapter is to describe emerging and
manufacturing techniques in the field of thermoset-
d composite materials. Various composites manufac-
iscussed in terms of their limitations, advantages,
eat and pressure, type of raw materials used, and
eters. The basic knowledge of these processes will
ight process for an application. Section 6.2 briefly
ring process selection criteria.
Process Selection Criteria
llenge for design and manufacturing engineers to
turing process for the production of a part, the reason
manufacturing engineers have so many choices in
and processing techniques to fabricate the part. This
s the criteria for selecting a process. Selection of a
application need. The criteria for selecting a process
ion rate, cost, strength, and size and shape require-
scribed below.
/Speed
ication and market needs, the rate of production is
he automobile market requires a high rate of produc-
0 units per year (40 per day) to 5,000,000 per year
aerospace market, production requirements are usu-
100 per year. Similarly, there are composites manu-
at are suitable for low-volume and high-volume
ts. For example, hand lay-up and wet lay-up processes
-volume production, whereas compression molding
ding are used to meet high-volume production needs.

6.2.2 Cost

Most consumer and aut
higher production costs
rials, process cycle tim
processing techniques t
ers are cost prohibitive.
and requires a thoroug
cost of a product is sig
well. For example, com
of steel for the fabricati
volume is less than 150,
is preferred. Various co
ters that affect the final

6.2.3 Performance

Each composite process
final properties of the p
strongly depends on fi
content (60 to 70% is s
composites provide mu
composites. Depending
thus a suitable composi

6.2.4 Size

The size of the structure
processes. The automob
nents compared to the
medium-sized compone
structures such as a bo
reveals the suitability o
product size.

6.2.5 Shape

The shape of a produ
production technique.
the manufacture of pre
very economical in pro
as circular and rectangu
Table 6.1 characterize
factors. The cost catego
equipment is running a
omobile markets are cost sensitive and cannot afford
. Factors influencing cost are tooling, labor, raw mate-
e, and assembly time. There are some composite
hat are good at producing low-cost parts, while oth-
Determining the cost of a product is not an easy task
h understanding of cost estimating techniques. The
nificantly affected by production volume needs as
pression molding (SMC) is selected over stamping
on of automotive body panels when the production
000 per year. For higher volume rates, steel stamping
st-estimating techniques, as well as various parame-
cost of the products, are discussed in Chapter 11.
utilizes different starting materials and therefore the
art are different. The strength of the composite part
ber type, fiber length, fiber orientation, and fiber
trongest, as a rule). For example, continuous fiber
ch higher stiffness and strength than shorter fiber
on the application need, a suitable raw material and
te manufacturing technique are selected.
is also a deciding factor in screening manufacturing
ile market typically requires smaller-sized compo-
aerospace and marine industries. For small- to
nts, closed moldings are preferred; whereas for large
at hull, an open molding process is used. Table 6.1
f composites manufacturing techniques in terms of
ct also plays a deciding role in the selection of a
For example, filament winding is most suitable for
ssure vessels and cylindrical shapes. Pultrusion is
ducing long parts with uniform cross-section, such
lar.
s each manufacturing method based on the above
ry of the part is shown when the manufacturing
t full capacity.

TABLE 6.1

Manufacturing Process Selection Crite

Process
Production
Speed Co aterial

Filament winding
Pultrusion
Hand lay-up
Wet lay-up
Spray-up
RTM
SRIM
Compression
molding
Stamping
Injection molding
Roll wrapping
Slow to fast
Fast
Slow
Slow
Medium to
fast
Medium
Fast
Fast
Fast
Fast
Medium
to fast
Low t
high
Low t
med
High
Mediu
Low
Low t
med
Low
Low
Mediu
Low
Low t
med
with epoxy and
, usually with
ylester resins
with epoxy resin
olyester and
talyzed resin
c with vinylester
with
resin
d (e.g., SMC,
d with
pe)
with
© 2002 by CRC Press LLC
ria
st Strength Size Shape Raw M
o
o
ium
m
o
ium
m
o
ium
High
High (along
longitudinal
direction)
High
Medium to high
Low
Medium
Medium
Medium
Medium
Low to medium
High
Small to large
No restriction on
length; small to
medium size
cross-section
Small to large
Medium to large
Small to medium
Small to medium
Small to medium
Small to medium
Medium
Small
Small to medium
Cylindrical and
axisymmetric
Constant
cross-section
Simple to complex
Simple to complex
Simple to complex
Simple to complex
Simple to complex
Simple to complex
Simple to contoured
Complex
Tubular
Continuous fibers
polyester resins
Continuous fibers
polyester and vin
Prepreg and fabric
Fabric/mat with p
epoxy resins
Short fiber with ca
Preform and fabri
and epoxy
Fabric or preform
polyisocyanurate
Molded compoun
BMC)
Fabric impregnate
thermoplastic (ta
Pallets (short fiber
thermoplastic)
Prepregs

The process selection
fabrication choices. For
terms of the above vari

6.3 Product Fabric

To make a part, the fou
1. Raw material
2. Tooling/mold
3. Heat
4. Pressure
Depending on the ma
is chosen and laid on th
transform the raw mate
ments are different for
metals or thermoplastic
for processing, whereas
the melting temperatur
sure required for proce
requires higher tempera
which melts at around 5
ing the shape as compa
temperatures in the ra
amounts of heat and pr
sets are in the liquid s
form and process. Ther
The temperature requir
and cure kinetics. In c
required for proper con
The higher pressure a
ing process need strong
In addition to higher t
requirements mandate
increased processing co
during SMC molding re
more than $1 million. T
requires extremely low
in order to obtain signi
Every process require
final shape. Therefore,
criteria in Table 6.1 are useful in prescreening of the
the final selection of a process, a detailed study in
ables (e.g., cost, speed, and size) is performed.
ation Needs
r major items needed are:
nufacturing process selected, a suitable raw material
e tool/mold. Then, heat and pressure are applied to
rial into the final shape. Heat and pressure require-
different material systems. Solid materials such as
s require a large amount of heat to melt the material
thermosets require less heat. In general, the higher
e of a material, the higher the temperature and pres-
ssing. For example, steel, which melts at 1200°C,
tures and pressures to process the part. Aluminum,
00°C, requires less heat and pressure for transform-
red to steel processing. Thermoplastics have melting
nge of 100 to 350°C and therefore require lesser
essure as compared to steel and aluminum. Thermo-
tate at room temperature and therefore are easy to
mosets require heat for rapid curing of the material.
ement for thermosets depends on resin formulation
omposites, fibers are not melted and thus heat is
solidation of the matrix materials only.
nd temperature requirements during a manufactur-
and heavy tools, which increase the cost of tooling.
ooling costs, the higher pressure and temperature
special equipment, which is another source of
st. For example, the higher pressure requirement
quires large and bulky equipment and usually costs
he ideal manufacturing process will be the one that
amounts of heat and pressure and is quick to process
ficant processing cost savings.
s a set of tools to transform the raw material to the
the success of a production method relies on the

quality of the tool. Sect
methods for making var
industry. The knowledg
in understanding the to
techniques.

6.4 Mold and Tool

The three most critical s
processing engineering
independent, and prod
straints of the mold-mak
can draw a wonderful d
be manufactured econo
Mold- and tool-makin
ufacturing area. A tool t
the tool or mold, the ra
and size requirements o
The type of tool requi
technique. For example
material, RTM uses a cl
process uses an FRP mo
The quality and surface
of the tool. Section 6.4.1

6.4.1 Mold Design Cr

6.4.1.1 Shrinkage Al

In mold design, shrink
to make sure that the en
part is cured. Shrinkag
caused by curing the re
For a composite materia
is determined and facto

6.4.1.2 Coefficient o
and End Prod

The coefficient of therm
the mold design. Every
when heated and coole
and the composite part
ion 6.4 discusses design parameters and fabrication
ious types of commonly used tools in the composites
e provided in the following section will be helpful
oling needs for various composites manufacturing
Making
teps
in developing a new product are product design,
, and mold engineering. Obviously, these are not
uct design engineers need to think about the con-
ers and manufacturing engineers. Product designers
esign with very good aesthetics, but if the part cannot
mically, then there is no point to that great design.
g are a challenging segment of the composites man-
ransforms the raw material to a given shape. Without
w material cannot be shaped to the final dimension
f the part.
rement depends on the selection of a manufacturing
, filament winding uses mandrels for laying the raw
osed mold, pultrusion uses a die, and the wet lay-up
ld for providing the desired shape in the final part.
finish of the part heavily rely on the surface finish
identifies the important criteria for mold design.
iteria
lowance
age of the composite material is taken into account
d product is of the desired size and shape after the
e is the reduction in volume or linear dimensions
sin as well as by thermal contraction of the material.
l as well as mold material, the shrinkage allowance
red into the design of the part and the mold.
f Thermal Expansion of Tool Material
uct
al expansion (CTE) is an important parameter for
material expands and contracts to a different extent
d from a certain temperature. The CTE of the tool
should closely match to avoid residual stresses and

dimensional inaccuraci
system, the CTE consid

6.4.1.3 Stiffness of t

During part fabrication,
in closed molding oper
deform; otherwise, it m
stiff enough to take pro

6.4.1.4 Surface Finis

The surface finish of th
the tool. To obtain Class
be of high quality. Dur
removed to avoid the in
for the pultrusion proce
parts have extremely hi

6.4.1.5 Draft and Co

On vertical surfaces, a 1
promotes better materia
mold. Sharp corners m
mum inside corner rad
0.06 in. are recommend
as for ease in part remo

6.4.2 Methods of Ma

6.4.2.1 Machining

Machining a block of m
for small- to medium-s
pultrusion, and molds f
using this process. To m
to obtain the desired d
and chrome plated to ge
for the various molding
and machined using CN
Data from finite elemen
model is transferred int
For complicated shape
generate the mold surf
or plunge, used for mak
as needed for stamping
injection molding opera
es in the end product. For a room-temperature cure
eration is not important.
he Mold
the mold experiences significant pressure, especially
ations. Under such pressures, the mold should not
ay cause distortion in the part. The mold should be
cessing pressures.
h Quality
e end product relies on the surface finish quality of
A surface finish on the part, the tool surface should
ing part fabrication, the tool is waxed and dirt is
clusion of any foreign material in the part. The die
ss, and molds for making boat hulls and automotive
gh surface quality.
rner Radii
° draft angle is recommeded. A generous draft angle
l flow, reduced warpage, and easier release from the
ust be avoided during mold and part design. Mini-
ii of 0.08 in. and minimum outside corner radii of
ed for better material flow along the corner as well
val.
king Tools
aterial is more common in making molds and tools
ized parts. Mandrels for filament winding, dies for
or compression molding, RTM, and SRIM are made
ake a mandrel, a steel rod is taken and then machined
iameter. The surface of the mandrel is then ground
t a smooth and glossy surface finish. To make molds
processes, metal blocks (mostly tool steels) are taken
C and a grinding machine to get the desired shape.
t (FE) analysis or a CAD (computer-aided design)
o the machine and the desired surface is generated.
s, electrical discharge machining (EDM) is used to
ace. The two main types of EDM are termed sinker
ing mold or die cavities, and wire, used to cut shapes
dies. EDM is very common for making molds for
tions. For closed molding operations such as RTM,

SRIM, and injection mo
for feeding and escapin
functions: to allow air t
filling with the resin ma
into the mold. Closed m
near-net-shape parts.
For prototype buildin
materials are machined

6.4.2.2 FRP Tooling

Fiber reinforced plastic
molding operations su
cesses. Open molds are
which composite comp
plug) from which the m
product. The master p
automotive fender, or h
of metal, wood, plast
Figure 6.1. Creation of m
ing is shown in Figures
defect-free to reduce th
Once the master mod
removal of the mold. T
times in alternate directi
The next step is to ap
The tooling gel coat pro

FIGURE 6.1

Illustration of steps in makin
(b) master model after machi
lding, inlet and outlet ports or gates are provided
g of raw material. The outlet port (vent) has two
o escape from the mold and to ensure proper mold
terial. Heating and cooling devices are incorporated
olding operations allow production of net-shape or
g operations, wood, styrofoam, plastic, and other
and used as molds.
for Open Molding Processes
(FRP) toolings are primarily manufactured for open
ch as hand lay-up, wet lay-up, and spray-up pro-
made from a master pattern. Both the molds with
onents are built and the master pattern (models or
olds are created are critical to the quality of end
attern could be an existing part such as boat hull,
atch cover, or could be made by machining a block
ic, foam, or any other material as shown in the
aster model from a solid board by machine process-
6.1a and b. The master model should be glossy and
e amount of sanding and buffing on the mold.
el is ready, it is waxed with release agent for easy
he master is coated with release wax three or four
ons and allowed to harden after each layer is applied.
g a finished master model and laminated mold: (a) solid board;
ning; (c) laminated molds with backup; and (d) finished mold.
(c) (d)
(a) (b)
ply a tooling gel coat on the surface of the master.
vides a hard, glossy, and long-lasting surface on the

mold. It is applied usin
allowed to gel before a
gel coat has properly g
the finger does not stic
gel surface, it is ready fo
is used to laminate sho
can also be used for la
generally used for lami
up process or combinat
making the mold. For l
core material is embedd
ture. Various types of t
as a backing material fo
Once the mold is pr
called a cradle to supp
also used to support th
steel; however, it is imp
attachment. This can be
the cradle. Spacers can
wherever the cradle co
into the mold using fab
does not seep through
Figure 6.2 is a photo
laminated molds with b
shows the prototype of
mark 80 liquid board. I
used as a filler materia
machined foam structu
modeling board elimin
and produces substanti

TABLE 6.2

CTE and Service Temp

Tooling Material

Stainless steel
Aluminum alloys
Room temp. cure carbon/
Intermediate temp. cure c
Carbon/cyanate ester pre
Carbon/BMI prepreg
Room temp. cure glass/ep
Intermediate temp. cure g
Epoxy-based tooling boar
Urethane-based tooling fo
g a brush or spraying equipment. The gel coat is
pplying any laminating material. To make sure the
elled, the surface is lightly touched with a finger. If
k or does not leave a slight fingerprint mark on the
r lamination. After the gel coat is ready, a spraygun
rt fiber composites. Prepreg material or wet fabric
mination. For aerospace applications, prepregs are
nation. For making bathtubs or boat hulls, a spray-
ion of spray-up and wet fabric lamination is used for
arge and stiffness-critical structures, wood or foam
ed into the lamination to achieve a sandwich struc-
ooling materials, as listed in Table 6.2, are available
r the mold.
epared, it is strengthened with a backup structure
ort the mold, as shown in Figure 6.1c. Egg-crate is
e mold. The cradle can be constructed of wood or
ortant that the cradle be insulated from the mold at
accomplished using spacers between the mold and
be made of cardboard, foam, or coremat and placed
mes into contact with the mold. The cradle is fixed
ric and resin lamination. Care is taken so that resin
the spacer material.
graph of a tool shop consisting of master models,
ackup structures, checking templates, etc. Figure 6.3
a car shape generated by CNC machining of aero-
nexpensive and lightweight 8-lb density foam was
l and 2-in. thick liquid board was applied over the
re. The use of this lightweight foam over a solid
eratures of Various Tooling Materials
CTE
(µin./in. -°F)
Maximum Service
Temperature
(°F)
epoxy prepreg
arbon/epoxy prepreg
preg
oxy prepreg
lass/epoxy prepreg
d
am
8–12
12–13.5
1.4
1.4
1.5–2.0
2.0–3.0
7.0–8.0
7.0–8.0
30–40
35–50
1000
300–500
300–400
300–400
450–700
450–500
300–400
300–400
150–400
250–300
ates the need for heavy and expensive base plates
al savings in material costs.

6.4.3 Tooling Guideli

For closed molding ope
the mold material shou
well as injection pressu
can be high enough to

FIGURE 6.2

Master models and laminated

FIGURE 6.3

Generation of a car shape fro
nes for Closed Molding Operations
rations such as RTM, SRIM, and injection molding,
ld be strong enough to take the clamping force as
molds. (Courtesy of Lucas Industries.)
m a liquid board. (Courtesy of Lucas Industries.)
re. Stresses induced by clamping forces on the mold
cause appreciable distortion on the part and mold.

They should be checke
to ensure that mold par
For closed molding ope
port location is very cri
computer models have
inside the mold. These
phase to predict the opt
injection sequencing in
of minimal inlet pressu
mold filling or dry spot
and allow the designer
puter — instead of the m
mold may have to be mo
are extensively used fo
for injection molding pr
els save significant mol
injection molding proce
common in injection

FIGURE 6.4

Two-plate mold for injection
Locating spring
Sprue bushing
Top clamp plate
d using conservative strength of materials analyses
t deflections do not cause out-of-tolerance moldings.
rations, creating a gate location or inlet and outlet
tical in the mold design. For RTM processes, various
been developed to numerically simulate resin flow
simulation models are used during the mold design
imal locations for inlet ports and vents, and optimal
the case of multiple ports, thus achieving the goals
re and fill time and the elimination of incomplete
s. Simulation models identify potential trouble spots
to evaluate various injection strategies on the com-
ore costly empirical approach, where an expensive
dified significantly or abandoned. Computer models
r thermoplastic injection molding processes. Molds
ocesses are very expensive and these computer mod-
d design cost. Figure 6.4 shows a two-plate mold for
ss. The two-plate mold is a simple form and is most
molding process.
Ejector pin
Cavity plate
Leader pin
Punch plate
Support plate
Ejector housing
Leader pin bushing
Molded part
molding industries. For the two-plate mold in

Figure 6.4, edge gates
sprue bushing and reac
sprue, runner, and gate
and with minimum pre
mity of flow refers to a
pressure at the cavity e
injection molding indus
mon and used when sm
sticks can be manufactu
duction cycle time of ab

large parts in an RTM p
ports. Multiple ports ar
need for high injection p
boards. The molds were
approximately 1400 vac
sheet immediately prior
snowboard. Figure 6.6 s
rackets. Prepreg was use
Tooling for aerodyna

FIGURE 6.5

Tooling for fiberglass/epoxy
are shown. The raw material is injected through a
hes the cavities through runners. The purpose of the
systems is to transfer liquid resin or melt uniformly
ssure and temperature drops in each cavity. Unifor-
n equal flow rate through each gate and thus equal
ntrance. Multiple cavities are quite common in the
try. In RTM, the use of multiple cavities is less com-
all parts are manufactured. For example, four hockey
red simultaneously in an RTM process with a pro-
out 14 min from molding to deloading.1 For making
rocess, single-cavity molds are made with multiple
e used to speed cycle times as well as mitigate the
ressures. Figure 6.5 shows a mold for making snow-
integrally heated and the lower mold half contains
uum vent holes for vacuforming a thermoplastic face
to lamination of the fiberglass/epoxy urethane cored
hows match molds for making carbon fiber tennis
snowboard. (Courtesy of Radius Engineering, Inc.)
d with an internal pressure bladder to make the part.
mic helicopter fairing components is shown in

FIGURE 6.6

Tooling for carbon fiber tenn
is racquet. (Courtesy of Radius Engineering, Inc.)

Figure 6.7. These cone a
dynamic fairings for he
structed of prepregged
content parts were pro
aluminum tools for mak
rotor part is shown at t
the RTM process. The to
halves of the mold and
mandrels placed inside
Carbon fabrics are wra
mold. The mold is then
part. After curing, the p

FIGURE 6.7

Tooling for aerodynamic helic
nd dome tools were used for the production of aero-
licopter external fuel tanks. The fairings were con-
fiberglass epoxy. High fiber volume and low void
duced in the matched tool sets. Figure 6.8 shows
ing helicopter tail rotor parts. The carbon/epoxy tail
he bottom of the photograph. This part is made by
p two items in Figure 6.8 show the upper and lower
the third item from the top shows three aluminum
the mold to create rib sections in the rotor part.
pped around these mandrels and placed inside the
opter fairing components. (Courtesy of Radius Engineering, Inc.)
closed and epoxy resin is injected to consolidate the
art is removed from the mold as are the mandrels.

Guidelines for design
operations include:
1. For thin-walled p
such as in hocke
flow distances an
2. Locate gates wh
along the greatest
a single gate, loca
locate gates on th
area into equal s
hockey sticks hav
min to complete t
from one end.

M
high in a single-g
multiple ports al
ports can be crea
with a film gate t
3. Avoid placing g
appearance of th

FIGURE 6.8

Tooling for making helicopte
(Courtesy of Radius Engineer
ing inlet ports or gate locations for closed molding
arts having large flow length-to-thickness ratios
y sticks, create two or more gates to obtain equal
d to avoid flow distribution problems.
ere the flow of resin or melt proceeds uniformly
dimension as shown in Figure 6.9. For a mold with
te the gate on the short side; and for multiple gates,
e long side, as shown in Figures 6.9, to divide the
ubsections. To make an 1-in. square, 52-in. long
ing 0.072-in. wall thickness, it might take about 30
he mold filling in an RTM process if resin is injected
oreover, the rejection rate for production may be
ate mold because of dry spots. To speed the process,
ong the length of the stick can be used. Multiple
ted using an injection runner parallel to the stick
hat transmits resin from the runner to the preform.
r tail rotor. The carbon/epoxy tail rotor is shown at the bottom.
ing, Inc.)
ates on the exposed side of the part where the
e part is crucial.

4. Locate gates in
critical in injecti
SMC parts. Weld
head-on or when
lines are the wea
high filling rate t
5. Position gates so
rally impelled th
plane.
6. Locate gates in s
filled late and ca
in Figure 6.11b,
unfilled zones o
avoided, especia
composites. In F
tance and avoids
7. Locate gates in t
sink marks. The
furthermost thin

FIGURE 6.9

Illustration of flow front for s
edge; and (b) flow front in m
such a way that weld lines are avoided. This is
on molding as well as compression molding of
lines result when two flow fronts come together
two parallel streams merge (Figure 6.10). Weld
ker area of the part and affect the appearance. A
ends to reduce the adverse effects of weld lines.
that the air displaced during resin flow is natu-
rough the vent (outlet port) or through the parting
uch a way so as to avoid stagnant areas that are
n have voids or dry spots (Figure 6.11). As shown
incoming resin can jet across the mold, leaving
f trapped air or voids. This scenario should be
lly in the case of injection molding of short fiber
igure 6.11a, the resin front experiences flow resis-
the problem of jetting.
he thickest section to avoid incomplete filling or
ingle and multiple cavities: (a) flow front in a single gate at short
ultiple gates.
(a)
(b)
n use a high injection speed to ensure that the
section is filled.

6.5 Basic Steps in

There are four basic s
ting/impregnation, lay-
manufacturing process
accomplished in differe

FIGURE 6.10

Illustration of weld lines dur

FIGURE 6.11

Recommended (a) and not re
Mold c
(a)
Mold
Inlet
a Composites Manufacturing Process
teps involved in composites part fabrication: wet-
up, consolidation, and solidification. All composites
ing mold filling process.
commended (b) gate locations.
avity
Inlet port
Mold
(b)
Mold cavity Mold cavityMold
Inlet
es involve the same four steps, although they are
nt ways.

6.5.1 Impregnation

In this step, fibers and
example, in a filament w
bath for impregnation.
impregnated by the ma
In a wet lay-up proce
squeezing roller for pr
make sure that the resi
tension, and capillary a
nation process. Thermo
10e4 cp are easier to we
of 10e4 to 10e8 cp an
impregnation.

6.5.2 Lay-up

In this step, composite l
or prepregs at desired
desired composite thick
and resin mixture. In
obtained by the relativ
prepreg lay-up process,
manually or by machin
architecture, either from
and resin is injected to
The purpose of this
dictated by the design.
on fiber orientation and

6.5.3 Consolidation

This step involves crea
or lamina. This step en
layers during processing
a good quality part. Poo
Consolidation of contin
cesses: resin flow throu

During the consolidatio
and fiber structure. Init
by the resin (zero fiber
mation when the compr
the boundary. There are

deformation and consid
resins are mixed together to form a lamina. For
inding process, fibers are passed through the resin
In a hand lay-up process, prepregs that are already
terial supplier in a controlled environment are used.
ss, each fabric layer is wetted with resin using a
oper impregnation. The purpose of this step is to
n flows entirely around all fibers. Viscosity, surface
ction are the main parameters affecting the impreg-
sets, which have viscosities in the range of 10 e1 to
t-out. Viscosities of thermoplastics fall in the range
d require a greater amount of pressure for good
aminates are formed by placing fiber resin mixtures
angles and at places where they are needed. The
ness is built up by placing various layers of the fiber
filament winding, the desired fiber distribution is
e motions of the mandrel and carriage unit. In a
prepregs are laid at a specific fiber orientation, either
e. In an RTM process, the preform has built-in fiber
a braiding operation or from some other machine,
form the laminate..
step is to achieve the desired fiber architecture as
Performance of a composite structure relies heavily
lay-up sequence.
ting intimate contact between each layer of prepreg
sures that all the entrapped air is removed between
. Consolidation is a very important step in obtaining
rly consolidated parts will have voids and dry spots.
uous fiber composites involves two important pro-
gh porous media and elastic fiber deformation.2,3
n process, applied pressure is shared by both resin
ially, however, the applied pressure is carried solely
elastic deformation). Fibers go through elastic defor-
essive pressure increases and resins flow out toward
various consolidation models4,5 that ignore the fiber
er only resin flow.

6.5.4 Solidification

The final step is solidifi
moplastics or may take
is maintained during thi
the production rate ach
rate of solidification de
Heat is supplied during
thermoset resins, usua
cross-linking process. In
solidification and there
In thermoplastics proces
rate of the process. In
obtain faster solidificat
perature is lowered to o
The above four steps
composites processing.
as creating a desired fib
turing methods; this is d
the advantages and disa
ites processing techniqu

6.6 Advantages an
and Thermopla

6.6.1 Advantages of T

The common thermose
materials could be one
liquid state at room te
elevated temperatures
shape. Manufacturing m
the following advantag
1. Processing of th
initial resin syste
2. Fibers are easy t
are less.
3. Heat and pressu
moset composite
energy savings.
4. A simple low-cos
composites.
cation, which may take less than a minute for ther-
up to 120 min for thermosets. Vacuum or pressure
s period. The lower the solidification time, the higher
ievable by the process. In thermoset composites, the
pends on the resin formulation and cure kinetics.
processing to expedite the cure rate of the resin. In
lly the higher the cure temperature, the faster the
thermoplastics, there is no chemical change during
fore solidification requires the least amount of time.
sing, the rate of solidification depends on the cooling
thermoset composites, the temperature is raised to
ion; whereas in thermoplastics processing, the tem-
btain a rigid part.
are common in thermoset as well as thermoplastic
The methods of applying heat and pressure, as well
er distribution, are different for different manufac-
iscussed in Sections 6.8 and 6.9. Section 6.6 discusses
dvantages of thermoset and thermoplastic compos-
es.
d Disadvantages of Thermoset
stic Composites Processing
hermoset Composites Processing
t resins are epoxy, polyester, and vinylester. These
-part or two-part systems and are generally in the
mperature. These resin systems are then cured at
or sometimes at room temperature to get the final
ethods for processing thermoset composites provide
es.
ermoset composites is much easier because the
m is in the liquid state.
o wet with thermosets, thus voids and porosities
re requirements are less in the processing of ther-
s than thermoplastic composites, thus providing
t tooling system can be used to process thermoset

6.6.2 Disadvantages o

1. Thermoset comp
thus results in lo
2. Once cured and
reformed to obta
3. Recycling of ther

6.6.3 Advantages of T

The initial raw materia
needs to be melted to ob
thermoplastic composit
1. The process cycl
chemical reaction
high-volume pro
for injection mold
for automotive-t
are usually high.
2. Thermoplastic co
application of he
3. Thermoplastic co

6.6.4 Disadvantages o

1. Thermoplastic co
processing. More
plastic composite
ing cost in the i
$50,000, whereas
less than $500.
2. Thermoplastic co
require sophistic

6.7 Composites M

Composites manufactu
main manufacturing cat
posites and manufactur
f
Thermoset Composites Processing
osite processing requires a lengthy cure time and
wer production rates than thermoplastics.
solidified, thermoset composite parts cannot be
in other shapes.
moset composites is an issue.
hermoplastic Composites Processing
l in thermoplastic composites is in solid state and
tain the final product. The advantages of processing
es include:
e time is usually very short because there is no
during processing, and therefore can be used for
duction methods. For example, process cycle time
ing is less than 1 min and therefore very suitable
ype markets where production rate requirements
mposites can be reshaped and reformed with the
at and pressure.
mposites are easy to recycle.
f Thermoplastic Composites Processing
mposites require heavy and strong tooling for
over, the cost of tooling is very high in thermo-
s manufacturing processes. For example, the tool-
njection molding process is typically more than
a mandrel for the filament winding process costs
mposites are not easy to process and sometimes
ated equipment to apply heat and pressure.
anufacturing Processes
ring processes can be broadly subdivided into two
egories: manufacturing processes for thermoset com-
ing processes for thermoplastic composites. In terms

of commercial applicati
posite market. About 75
resins. Thermoset com
thermoplastic counterp
moset composites as w
processing techniques. T
unsaturated polyester)
moplastic composites c
The manufacturing pr
the following headings
1. Major applicatio
2. Basic raw materi
3. Tooling and mol
4. Making of the pa
5. Methods of appl
6. Basic processing
7. Advantages of th
8. Limitations of th
We first discuss the m
posite parts under the a
cesses are then discusse

6.8 Manufacturing

In terms of commercial
made of thermoset com
automotive, marine, bo
several dominant therm
market, each with its pr
method are also include
available manufacturin
description of a process
process.

6.8.1 Prepreg Lay-Up

The hand lay-up proces
up and prepreg lay-up.
ons, thermoset composite parts dominate the com-
% of all composite products are made from thermoset
posite processes are much more mature than their
arts mainly because of the widespread use of ther-
ell as its advantages over thermoplastic composite
he first use of thermoset composites (glass fiber with
occurred in the early 1940s, whereas the use of ther-
ame much later.
ocesses described in this chapter are discussed under
:
ns of the process
als used in the process
d requirements
rt
ying heat and pressure
steps
e process
e process
anufacturing processes for making thermoset com-
bove eight headings. Thermoplastic composite pro-
d.
Processes for Thermoset Composites
applications, more than 75% of all composites are
posites. Their uses predominate in the aerospace,
at, sporting goods, and consumer markets. There are
oset composite processing methods available on the
os and cons. The advantages and limitations of each
d for each manufacturing process. The commercially
g techniques are described below. The order of
below does not mean the order of importance of the
Process
s is mainly divided into two major methods: wet lay-
The wet lay-up process is discussed in Section 6.8.2.

Here, the prepreg lay-u
industry, is discussed. I
bagging process. Comp
can be manufactured us
low-volume capability.
desired fiber orientation
bagging, the composite
and then heat and pres
part.
The prepreg lay-up o
costs are 50 to 100 times
high-volume processes
quantity runs, the prep
processes.

6.8.1.1 Major Applic

The prepreg lay-up proc
for making prototype pa
ing goods are made usin
radomes such as sharkno
wich constructions with
the nose and tail ends o
sandwich fairings for t

FIGURE 6.12

Variety of aircraft radomes. (
p process, which is very common in the aerospace
t is also called the autoclave processing or vacuum
licated shapes with very high fiber volume fractions
ing this process. It is an open molding process with
In this process, prepregs are cut, laid down in the
on a tool, and then vacuum bagged. After vacuum
with the mold is put inside an oven or autoclave
sure are applied for curing and consolidation of the
r autoclave process is very labor intensive. Labor
greater than filament winding, pultrusion, and other
; however, for building prototype parts and small
reg lay-up process provides advantages over other
ations
ess is widely used in the aerospace industry as well as
rts. Wing structures, radomes, yacht parts, and sport-
g this process. Figure 6.12 shows a variety of aircraft
se, conical, varying lengths, solid laminates, and sand-
dielectrically loaded foam cores. Radomes are used at
f aircraft. Figure 6.13 shows glass/epoxy/honeycomb
he airbus A330/340 flap tracks. Figure 6.14 shows
Courtesy of Marion Composites.)

landing gear doors for t
doors and four nose ge
being prepared for seco

FIGURE 6.13

Large glass/epoxy/honeycom
of Marion Composites.)

FIGURE 6.14

Main landing gear door being
he C-17 airlifter. Each plane requires eight main gear
ar doors. In Figure 6.14, the main landing gear door
b sandwich fairings for the Airbus 330/340 flap tracks. (Courtesy
prepared for second stage bond. (Courtesy of Marion Composites.)
nd stage bond is shown.

6.8.1.2 Basic Raw M

Graphite/epoxy prepre
prepreg lay-up process
their use is much less th
carbon/epoxy is much l
provides greater mass
widely used in the aer
factor, carbon fiber prep
cost, there is no signific
and other prepregs.
Other than epoxy, hig
ate, and BMI are also u

6.8.1.3 Tooling Requ

The tooling for the pr
prepregs are laid in the d
building purposes, tools
For the manufacture of
the composite tooling
bon/cyanate ester prep
glass/cyanate ester prep
Wide varieties of prepre
temperature cure, as lis
is also a common mater

6.8.1.4 Making of th

The raw material for th
erated. To make the com
and brought slowly to r
original package to avoi
temperature, it is cut to t
is placed on a cutting bo
prepreg is cut. For aeros
neat and clean atmosph
ditions. Dust is prohibit
heads, shoes, and body
cleanroom facility. For p
machines are used for c
the cutting table and
ultrasonic cutter, the pr
are computer controlled
The software minimizes
the ply cutting operatio
stacked together at on
aterials
gs are the most commonly used materials for the
. Glass/epoxy and Kevlar/epoxy are also used but
an carbon/epoxy prepregs. The main reason is that
ighter and stronger than other prepreg materials and
savings in the component. Because this process is
ospace industry, where weight is a critical design
reg is the material of choice. Moreover, in terms of
ant price difference between carbon/epoxy prepregs
h-temperature resins such as polyimides, polycyan-
sed in prepreg systems.
irements
epreg lay-up process is an open mold on which
esired fiber orientation and sequence. For prototype
are made by machining metals, woods, and plastics.
aerospace components, the tooling material is mostly
material such as carbon/epoxy prepregs, car-
regs, carbon/BMI prepregs, glass/epoxy prepregs,
regs, epoxy- and urethane-based tooling board, etc.
gs with room-temperature, intermediate-, and high-
ted in Table 6.1, are used for making the mold. Steel
ial for making tools for prepreg lay-up process.
e Part
is process is prepreg material, which is kept refrig-
posite part, prepreg is removed from the refrigerator
oom temperature. In general, thawing is done in the
d condensation. Once the prepreg is brought to room
he
desired length and shape. For cutting, the prepreg
ard and then, using a steel ruler and utility knife, the
pace applications, this operation takes place in a very
ere under controlled humidity and temperature con-
ed in the room. Workers are required to cover their
with clean clothing accessories. Figure 6.15 shows a
roduction parts of decent quantity, automated cutting
utting prepregs. In this case, the prepreg is laid on
using the reciprocating action of a knife, laser, or
epreg is cut into the desired pattern. These machines
and utilize software for ply cutting optimization.
scrap and provides repeatability and consistency in
n. The machine can cut several layers of prepregs
e time and thus creates efficiency. Predominantly

unidirectional fiber pre
such a way as to pro
prepregs made of fabric
Part fabrication is do
Release agent is applied
film is first removed fr
sequence dictated in th
and for parts of greater
sequence after every few

FIGURE 6.15

A cleanroom facility for comp
pregs are used for part fabrication. Plies are cut in
vide the desired fiber orientation. In some cases,
s are used.
ne by laying the prepregs on top of an open mold.
to the mold for easy removal of the part. The backing
om the prepreg and then prepregs are laid in the
e manufacturing chart. For aerospace components
safety issues, quality control personnel check the ply
osites part fabrication. (Courtesy of Lunn Industries.)
layers are laid down. After applying each prepreg

layer, it is necessary to e
are used to remove ent
Once all the prepregs
vacuum bagging prepa
and consolidation of th
1. Apply release fil
perforated film t
tiles to escape.
2. Apply bleeder, a
function of the b
ing from the stac
3. Apply barrier fi
release film exce
4. Apply breather l
function of the b
and at the same
5. The final layer is
film or reusable
stacked prepreg u
to enclose the en
0.5- to 1-in.-wide
the bagging mate
connected to a va
Peel ply fabrics are a
parts are to be adhesiv
good bondable surface

FIGURE 6.16

Vacuum bagging for prepreg
Dam
Prepregs
nsure that there is no entrapped air. Squeezing rollers
rapped air and to create intimate contact.
are laid in the desired sequence and fiber orientation,
rations are made as shown in Figure 6.16 for curing
e part. The steps required for vacuum bagging are:
m on top of all the prepreg. The release film is a
hat allows entrapped air, excess resins, and vola-
porous fabric, on top of the release film. The
leeder is to absorb moisture and excess resin com-
k of prepregs.
lm on top of the bleeder. The film is similar to
pt that it is not perforated or porous.
ayer, a porous fabric similar to the bleeder. The
reather is to create even pressure around the part
time allowing air and volatiles to escape.
a vacuum bag. It is an expendable polyamide (PA)
elastomer. This film is sealed on all sides of the
sing seal tape. If the mold is porous, it is possible
tire mold inside the vacuum bag. Seal tape is a
rubbery material that sticks to both the mold and
rial. A nozzle is inserted into the vacuum bag and
cuum hose for creating vacuum inside the bag.
pplied on the top of prepreg layers if consolidated
lay-up process.
Vacuum bag
Breather
Barrier
Bleeder
Release film
Sealant tape
Mold
ely bonded at a later stage. The peel ply creates a
on the fabricated part. Sometimes, co-curing of the

various parts is done to
the number of parts. Fi
inside an autoclave for
facility containing vario
See Section 6.8.1.5 on h
lay-up process. Once th
part is taken out.

FIGURE 6.17

Vacuum bagged aerospace pa

FIGURE 6.18

Manufacturing facility contai
eliminate any extra processing step and to reduce
gure 6.17 shows a vacuum bagged part ready to go
curing process. Figure 6.18 shows a manufacturing
us autoclaves.
ow heat and pressure are created during the prepreg
rt ready to go inside an autoclave. (Courtesy of Lunn Industries.)
ning various autoclaves. (Courtesy of Marion Composites.)
e part is cured, the vacuum bag is removed and the

6.8.1.5 Methods of A

After lamination and b
curing and consolidatio
maintain the desired pr
cessing of the composit
cure cycle depends on
geometry of the part.
The pressure is create
external pressure inside
inside the bagging mate
vacuum inside the bag,
vacuum pump using a
uum.
External pressure ins
air or nitrogen. Nitroge
high temperature to avo
the bag and the vacuum
the laminate against the
The heat for curing c
gas supplied to the cham
the autoclave. Cartridge
increasing the temperat
clave are controlled by
autoclave. The user sets
computer controls both
As shown in Figure 6.
then the temperature is

FIGURE 6.19

Typical cure cycle during the
Te
m
pe
ra
tu
re
(D
eg
.C
)
Hea
(1-4 deg
Apply vac
200
160
120
80
40
20
1
pplying Heat and Pressure
agging, the mold is placed inside an autoclave for
n. An autoclave, similar to a pressure vessel, can
essure and temperature inside the chamber for pro-
e. A typical cure cycle is shown in Figure 6.19. The
the type of resin material and the thickness and
d in two ways: using the vacuum bag as well as the
the autoclave. The vacuum bag creates a vacuum
rial and thus helps in proper consolidation. To create
the nozzle in the bagging system is connected to the
hose. The vacuum pump generates the desired vac-
ide the autoclave is created by injecting pressurized
n is preferred for cases in which curing is done at
id burning or fire. Thus, the external pressure outside
inside the bag creates sufficient pressure to compact
mold and create intimate contact between each layer.
omes from heated air or nitrogen. The pressurized
ber comes heated to increase the temperature inside
heaters can also be placed inside the autoclave for
ure. The temperature and pressure inside the auto-
computer-controlled equipment located outside the
up the cure profile as shown in Figure 6.19 and the
parameters using an on/off switch.
autoclave process.
Hold 90 +15
-0 min
Cool down
(3 deg. C/min)
Dwell
t up
. C/min) Apply pressure 85 psi (588 kPa)
Time (hours)
uum 22 inches (74 kPa) Hg minimum
2 3 4 5
19, vacuum is applied in the bagging system first and
raised to a level to increase the resin flow. The heating

rate is usually 2°C/min
temperature, the tempe
the composites. During
bagging system and mai

6.8.1.6 Basic Process

The basic steps in makin
are summarized as follo
1. The prepreg is re
temperature for
2. The prepreg is la
and orientation.
3. The mold is clea
surface.
4. Backing paper fr
on the mold surf
ing chart.
5. Entrapped air be
ing roller after ap
6. After applying a
ments are made
breather, and bag
7. The entire assem
if the structure is
8. Connections to t
the autoclave do
9. The cure cycle da
and followed.
10. After cooling, the

6.8.1.7 Typical Manu

Some of the challenges t
lay-up process are listed
1. Maintaining acc
because prepreg
ment equipment
2. Obtaining void-f
are caused by en
3. Achieving warpa
up process is cha
stresses during p
to 4°C/min. After dwelling for some time at the dwell
rature is further raised to another level for curing of
this stage, pressure is applied to the outside of the
ntained for about 2 hr, depending on the requirements.
ing Steps
g composite components by prepreg lay-up process
ws.
moved from the refrigerator and is kept
at room
thawing.
id on the cutting table and cut to the desired size
ned and then release agent is applied to the mold
om the prepreg is removed and the prepreg is laid
ace in the sequence mentioned in the manufactur-
tween prepreg sheets is removed using a squeez-
plying each prepreg sheet.
ll the prepreg sheets, vacuum bagging arrange-
by applying release film, bleeder, barrier film,
ging materials as mentioned in Section 6.8.1.5.
bly is then placed into the autoclave using a trolley
large.
hermocouples and vacuum hoses are made and
or is closed.
ta are entered into a computer-controlled machine
vacuum bag is removed and the part is taken out.
facturing Challenges
hat manufacturing engineers face during the prepreg
below.
urate fiber orientations in the part is difficult
s are laid down by hand. Automated tape place-
can be used for precise fiber orientation control.
ree parts is a challenge during this process. Voids
trapped air between layers.
ge- or distortion-free parts during the prepreg lay-
llenging. Warpage is caused by built-in residual
rocessing.

6.8.1.8 Advantages o

The prepreg lay-up pro
offers the following adv
1. It allows product
composite parts
have more than
2. Simple to comp
process.
3. This process is ve
advantage of low
investment for th
4. Very strong and

6.8.1.9 Limitations o

Although prepreg lay-u
1. It is very labor in
duction applicati
2. The parts produc

6.8.2 Wet Lay-Up Pro

In the early days, the
method for the making o
industry as well as for m
and has concerns for st
this process, liquid resi
placed on top. A roller is
resin and reinforcement
It is a very flexible proce
different types of fabri
placed manually, it is
requires little capital in

6.8.2.1 Major Applic

On a commercial scale,
mill blades, storage tan
plicity and little capital
prototype parts. Test cou
of reinforcements as w
complex shapes can be
9-in. and 27-ft, 1-in. sp
f the Prepreg Lay-Up Process
cess is very common in the aerospace industry and
antages:
ion of high fiber volume fraction (more than 60%)
because of the use of prepregs. Prepregs usually
60% fiber volume fraction.
lex parts can be easily manufactured using this
ry suitable for making prototype parts. It has the
tooling cost but the process requires high capital
e autoclave.
stiff parts can be fabricated using this process.
f the Prepreg Lay-Up Process
p is a mature process, it has the following limitations:
tensive and is not suitable for high-volume pro-
ons.
ed by the prepreg lay-up process are expensive.
cess
wet lay-up process was the dominant fabrication
f composite parts. It is still widely used in the marine
aking prototype parts. This process is labor intensive
yrene emission because of its open mold nature. In
n is applied to the mold and then reinforcement is
used to impregnate the fiber with the resin. Another
layer is applied until a suitable thickness builds up.
ss that allows the user to optimize the part by placing
c and mat materials. Because the reinforcement is
also called the hand lay-up process. This process
vestment and expertise and is therefore easy to use.
ations
this process is widely used for making boats, wind-
ks, and swimming pools. Because of its process sim-
investment, this process is widely used for making
pons for performing various tests for the evaluation
ell as resins are made using this process. Simple to
made using this process. Figure 6.20 shows a 41-ft,
ort boat and Figure 6.21 shows a 41-ft cruiser boat

FIGURE 6.20

Sports boats having a 41-ft, 9
tom); approximate dry weig
(Courtesy of Thunderbird Pro

FIGURE 6.21

A 41-ft cruiser boat; approxim
Products, Decatur, IN.)
-in. centerline length (top) and 27-ft, 1-in. centerline length (bot-
hts are 13,100 lb (5942 kg) and 5250 lb (2381 kg), respectively.
ducts, Decatur, IN.)
ate dry weight is 18,520 lb (8401 kg). (Courtesy of Thunderbird

made using this proces
of foam core to a 72-ft ya
by laminating fiberglas
Built-in wooden frames
skin panel without an
framings are complex an
support larger spans th

FIGURE 6.22

A 72-ft yacht. (Courtesy of M

FIGURE 6.23

Crew members applying cros
San Diego, CA.)
s. A 72-ft yacht is shown in Figure 6.22. Application
cht is shown in Figure 6.23. The hulls are constructed
s layers with core materials such as balsa or foam.
may be provided to strengthen the hull. In a single
y core material, the longitudinal and transverse
ikelson Yachts, San Diego, CA.)
s-linked foam core to a 72-ft yacht. (Courtesy of Mikelson Yachts,
d heavier than sandwich panel. Sandwich panel can
an single skin panels.

6.8.2.2 Basic Raw M

Woven fabrics of glass
material, with E-glass p
ester, and vinylester res
ing on the requirements
in building boats and o
in the making of boat h
laid over the mold.

6.8.2.3 Tooling Requ

The mold design for th
other manufacturing pr
temperature cure envir
other materials are use
mold can be a male or f
is used. In the boating i
(fiber-reinforced plastic
mold is stiffened by a w
of a male pattern. Seve
mold. The length of the
mold secondaries such

6.8.2.4 Making of th

A schematic of the wet
thickness of the compos
layers and liquid resin
and create uniform dist
squeezing action of the

FIGURE 6.24

Schematic of the wet lay-up p
aterials
, Kevlar, and carbon fibers are used as reinforcing
redominating in the commercial sector. Epoxy, poly-
ins are used during the wet lay-up process, depend-
of the part. Polyester resin is the most common resin
ther commercial items. Glass rovings are also used
ulls. The roving is chopped using a spraygun and
irements
e wet lay-up process is very simple as compared to
ocesses because the process requires mostly a room-
onment with low pressures. Steel, wood, GRP, and
d as mold materials for prototyping purposes. The
emale mold. To make shower bathtubs, a male mold
ndustry, a single-sided female mold made from FRP
) is used to make yacht hulls. The outer shell of the
ood frame. The mold is made by taking the reversal
ral different hull sizes can be made using the same
mold is shortened or lengthened using inserts and
as windows, air vents, and propeller tunnels.
e Part
lay-up process is shown in Figure 6.24, where the
ite part is built up by applying a series of reinforcing
layers. A roller is used to squeeze out excess resin
ribution of the resin throughout the surface. By the
roller, homogeneous fiber wetting is obtained. The
Mold
Resin
Roller
Fabric
rocess.

part is then cured mos
removed from the mold
The overall process cy
well as the resin formu
room-temperature curin
thick, then the wall thic
take place without over
finish off the day’s wor
expose a clean and bett
Quality control in the
of the final part is high
an important one for th
gent emissions regulati
use of closed mold alte
To obtain further insig
using this technique is
To make a boat hull
mold surface to facilitat
using a brush or sprayg
and provides coloring
and includes a thixotro
color finish. The gel coa
The gel coat provides a
gel coat hardens, a skin
improved corrosion and

than a layer of chopped
is almost double the co
corrosion resistance tha
overnight. The cured sk
Lamination begins the
laying it on the mold su
Usually, two stitched b
the hull, are placed on
worked into the reinfo
fabric is placed into spo
terline and seacock pen
that there is no dry fibe
and uniformly wetting
more efficient, the fabr
mold, or an in-house
im
resin on the fabric and
machine, as shown in
which wet the fabric. A
glass ratio. With this
machine can wet lamin
tly at room temperature and, once solidified, it is
.
cle time is dictated by the size of the component as
lation used. For large-sized structures such as boats,
g is commonly used. If the laminate to be made is
kness is built up in stages to allow the exotherm to
heating. Under these circumstances, it is common to
k with a peel ply, which is subsequently removed to
er surface for bonding the next layer.
wet lay-up process is relatively difficult. The quality
ly dependent on operator skill. The process remains
e boat-building process, although increasingly strin-
ons are forcing several manufacturers to explore the
rnatives such as RTM and VARTM.
ht into the wet lay-up process, boat hull fabrication
discussed here.
using this process, a release agent is applied to the
e the demolding operation. A gel coat is then applied
un. The gel coat improves the surface finish quality
as needed. A polyester gel coat is commonly used
pic additive and the pigmentation for the desired
t is then cured to avoid print-through of the laminate.
Class A surface finish on the hull surface. Once the
coat is applied using a spray-up process to obtain
chemical resistance.6 The skin coat is nothing more
glass mat with vinylester resin. Although vinylester
st of polyester resin, it is used because it has better
n polyester. After applying the skin coat, it is cured
in coat acts as a barrier to the structural laminate.
next day by cutting stitched bidirectional fabric and
rface in such a way that it covers the entire surface.
idirectional fabric layers, depending on the size of
the mold as a first laminating skin. Resin is then
rcement using a brush, roller, or flow coater. Extra
ts that require additional strength, such as the cen-
etrations. It depends on worker skill to make sure
r or entrapped air. The process of applying the resin
the fiber is very labor intensive. To make the process
ic is first wetted on a table and then placed on the
pregnating machine is used to uniformly apply the
then it is placed on the mold. In an impregnating
Figure 6.25, the fabric passes through two rollers,
fabric impregnator precisely controls the resin-to-
machine, rapid lamination can be achieved. The
ate about 1000 lb per hour.

After fiber wet-out, th
process, adhesive is sp
suitable core, is applied
is then vacuum bagged
done at a pressure of ab

FIGURE 6.25

Fabric impregnator demonstr
Engine Works, Pompano Bea

FIGURE 6.26

Demonstration of vacuum ba
to-core bond and low resin c
Beach, FL.)
e laminate is allowed to cure. Following the curing
read over the laminate and then balsa core, or any
to create a sandwich structure. The entire structure
as shown in Figure 6.26. The vacuum bagging is
ating impregnation of a glass fabric. (Courtesy of Merritt Boat and
ch, FL.)
gging of core materials. Vacuum bagging provides a tight skin-
ontent. (Courtesy of Merritt Boat and Engine Works, Pompano
out 15 in. Hg for 2 hr. Vacuum bagging ensures good

contact between the cor
final skin layer is lamin
The fabric is impregna
laminated skin was pre
ture. The total thickness
motor mounts, stringer
the mold.
The major limitation
one smooth surface. Th
fiber content, and surfa
are typically for very lo
critical.

6.8.2.5 Methods of A

The wet lay-up process
tions. The resin is norm
night curing, dependin
shortened by blowing w
rollers during laminatio
or sometimes vacuum b
the layers as well as to
be put into an autoclav
entire assembly is some

6.8.2.6 Basic Process

The major processing s
1. A release agent i
2. The gel coat is a
outer surface. Th
is placed.
3. The reinforcemen
is impregnated w
directly on the m
4. Using a roller, re
5. Subsequent reinf
is built up.
6. In the case of san
core is placed on
Rear-end lamina
skin was built up
7. The part is allow
temperature.
e and the laminate. On top of the core material, the
ated by placing about two bidirectional fabric layers.
ted with the resin in the same manner as the first
pared. The laminate is then cured at room tempera-
of the hull thus obtained is about 1.5-in. Bulkheads,
s, and decks are assembled while the hull is still in
of wet lay-up process is that the molding has only
e lack of control over part thickness, void fraction,
ce quality on the rear face means that applications
w stressed parts where dimensional accuracy is non-
pplying Heat and Pressure
is normally done under room-temperature condi-
ally left at room temperature for a day or for over-
g on the resin chemistry. The cure time can be
arm air on the laminate. Pressure is applied using
n. During the curing process, there is no pressure,
agging is used to create good consolidation between
remove entrapped air. If the part size is small, it can
e and external pressure is applied. Post-curing of an
times done to improve part performance.
ing Steps
teps in the wet lay-up process include:
s applied to the mold.
pplied to create a Class A surface finish on the
e gel coat is hardened before any reinforcing layer
t layer is placed on the mold surface and then it
ith resin. Sometimes, the wetted fabric is placed
old surface.
sin is uniformly distributed around the surface.
orcing layers are placed until a suitable thickness
dwich construction, a balsa, foam, or honeycomb
the laminated skin and then adhesively bonded.
ted skin is built similar to how the first laminated
.
ed to cure at room temperature, or at elevated

6.8.2.7 Advantages o

The wet lay-up process
niques with the followi
1. Very low capital
there is negligibl
2. The process is v
can be selected w
3. The cost of maki
can be used to m
for this process i
less expensive th

6.8.2.8 Limitations o

The wet lay-up process
1. The process is la
2. The process is mo
large structures.
3. Because of its ope
4. The quality of the
5. High fiber volum
this process.
6. The process is no

6.8.3 Spray-Up Proce

The spray-up process is
being in the method of
The wet lay-up process
materials are applied m
to apply resin and reinf
delivered per hour. In t
fiber glass and resin/ca
continuous fiber roving
it through a resin/cata
much faster than the we
it utilizes rovings, whic

6.8.3.1 Major Applic

The spray-up process is
parts in low- to medium
f the Wet Lay-Up Process
is one of the oldest composite manufacturing tech-
ng advantages:
investment is required for this process because
e equipment cost as compared to other processes.
ery simple and versatile. Any fiber type material
ith any fiber orientation.
ng a prototype part is low because a simple mold
ake the part. In addition, the raw material used
s liquid resin, mat, and fabric material, which are
an prepreg materials.
f the Wet Lay-Up Process
has the following limitations:
bor intensive.
stly suitable for prototyping as well as for making
n mold nature, styrene emission is a major concern.
part produced is not consistent from part to part.
e fraction parts cannot be manufactured using
t clean.
ss
similar to the wet lay-up process, with the difference
applying fiber and resin materials onto the mold.
is labor intensive because reinforcements and resin
anually. In the spray-up process, a spraygun is used
orcements with a capacity of 1000 to 1800 lb material
his process a spraygun is used to deposit chopped
talyst onto the mold. The gun simultaneously chops
s in a predetermined length (10 to 40 mm) and impels
lyst spray onto the mold. The spray-up process is
t lay-up process and is less expensive
choice because
h is an inexpensive form of glass fiber.
ations
used to make small to large custom and semi-custom
-volume quantities. Where the strength of the product

is not as crucial, spray-
pools, boat hulls, storag
niture components such
process.

6.8.3.2 Basic Raw M

The reinforcement mate
chopped to a length o
improved mechanical p
fiber layers is used. The
and Kevlar rovings can
various types of core m
The weight fraction of
of the total weight of th
The most common re
purpose or DCDP poly
used in this process. Fa
typically used. The res
most common fillers are
rials. In filled resin syst
25% filler is used by we

6.8.3.3 Tooling Requ

The mold used in this
process. Male and fem
Tubs and showers utiliz
female molds. To make
make the mold is descr

6.8.3.4 Making of th

The processing steps us
in the wet lay-up proce
to the mold and then a
2 hr, until it hardens. On
the fiber resin mixture o
incoming continuous r
length and impels it
Figure 6.27. Figure 6.28
by a robot. Resin/cataly
or just in front of the g
and catalyst inside the
concerns of the operato
two side nozzles into t
up is the more suitable option. Bathtubs, swimming
e tanks, duct and air handling equipment, and fur-
as seatings are some of the commercial uses of this
aterials
rial for this process is glass fiber rovings, which are
f 10 to 40 mm and then applied on the mold. For
roperties, a combination of fabric layers and chopped
most common material type is E-glass, but carbon
also be used. Continuous strand mat, fabric, and
aterials are embedded by hand whenever required.
reinforcement in this process is typically 20 to 40%
e part.
sin system used for the spray-up process is general-
ester. Isophthalic polyester and vinylesters are also
st-reacting resins with a pot life of 30 to 40 min are
in often contains a significant amount of filler. The
calcium carbonate and aluminum trihydrate mate-
ems, fillers replace some of the reinforcements; 5 to
ight.
irements
process is identical to that used in the wet lay-up
ale molds are used, depending on the application.
e male molds, whereas boat hulls and decks utilize
bathtubs, FRP molds are used. The method used to
ibed in Section 6.4.3.
e Part
ed in the spray-up process are very similar to those
ss. In this process, the release agent is first applied
layer of gel coat is applied. The gel coat is left for
ce the gel coat hardens, a spraygun is used to deposit
nto the surface of the mold. The spraygun chops the
ovings (one or more rovings) to a predetermined
through the resin/catalyst mixture as shown in
shows the application of chopped fibers and resin
st mixing can take place inside the gun (gun mixing)
un. Gun mixing provides thorough mixing of resin
gun and is preferred to minimize the health hazard
r. In the other type, the catalyst is sprayed through
he resin envelope. Airless sprayguns are becoming

FIGURE 6.27

Schematic of the spray-up pr

FIGURE 6.28

Robotic spray-up process for
gel. (Courtesy of Fanuc Robo
ocess.
Mold
Spraygun
Laminate
making a bathtub. The robot is applying chopped fiberglass with
tics.)

popular because they p
emission of volatiles. I
dispense the resin thro
into small droplets wh
In an air-atomized spra
resin.
In the spray-up proce
ing pattern, and the qua
the material is sprayed
entrapped air as well a
tinuous strand mats are
requirements. The curin
of resin can take 2 to 4 h
the part is demolded an
To gain a better und
described here for the fa
available on the market
an acrylic finish.

In bo
applied on the mold and
laminate material. The
finished tub but they are
based tubs are dominan
gel coat-finished tubs

manufacturing of gel c
release agent to the mal
gel coat is highly pigm
filled with minerals, tal
of the gel coat is to get a
the gel coat hardens, a
print-through. Both the
oven.
In acrylic-finished tu
make the tubs. The acr
onto the female mold. A
the mold. The hardened
male mold. The acrylic
composite materials are
of the tub. From here o
acrylic-based tubs are t
For the spray-up proc
used. Calcium carbonat
resin and mixed using
added into the resin to
wax rises to the laminat
film, which reduces sty
is pumped to the hold
rovide more controlled spray patterns and reduced
n an airless system, hydraulic pressure is used to
ugh special nozzles that break up the resin stream
ich then become saturated with the reinforcements.
ygun system, pressurized air is used to dispense the
ss, the thickness built up is proportional to the spray-
lity of the laminate depends on operator skill. Once
on the mold, brushes or rollers are used to remove
s to ensure good fiber wetting. Fabric layers or con-
added into the laminate, depending on performance
g of the resin is done at room temperature. The curing
r, depending on the resin formulation. After curing,
d tested for finishing and structural requirements.
erstanding of the spray-up process, the process is
brication of bathtubs. There are two types of bathtubs
: one with a gel coat surface finish and the other with
th of these products, the gel coat or acrylic is first
then the composite material is applied as a backing
thicker acrylic finish base is sturdier than a gel coat-
about $100 more expensive. For this reason, acrylic-
t in luxury items such as whirlpool baths, whereas
dominate the broader commodity market.7 In the
oat-finished bath tubs, the first step is to apply the
e mold and then apply the isopolyester gel coat. This
ented with titanium white (titanium dioxide) and
cs, and silica to reduce styrene content. The purpose
very high polished surface finish on the part. Once
black-pigmented barrier coat is applied to stop fiber
gel coat and the barrier coat are then cured in an
bs, instead of male mold, a female mold is used to
ylic sheet is heated first and then vacuum formed
fter the acrylic sheet solidifies, it is removed from
acrylic sheet is now sufficiently rigid to work as a
sheet is supported on a matched form and then
applied. The acrylic sheet becomes an integral part
nward, all the manufacturing steps for gel coat- and
he same.
ess, dicyclopentadiene (DCPD) polyester resins are
e and aluminum trihydrate fillers are added into the
a high shear mixing unit. A wax-type additive is
suppress styrene emission during lamination. The
ing surface during the cure cycle and creates a barrier
rene evaporation to less than 20%. The mixed resin
ing tank, which is connected to the spraygun. A

fiberglass chopper, whic
gun. Then the mixture
onto the barrier coat in
catalyst depends on the
layer of lamination, wo
is paid to radii and corn
Once the first skin or
wood is applied to ke
structure. The core ma
bottom of the part. The
temperature. After curi
same procedure. The sa
the second laminate. T
temperature. The mold
manufacturing cycle.
Finishing work is do
holes for drains and gr
according to the require
material control purpos
tural soundness, and su
identification, crated, an

6.8.3.5 Methods of A

The spray-up process i
need for heat or pressur
oven cured for higher
the curing process. Aft
used to remove the ent
laminate surface.

6.8.3.6 Basic Process

The steps used in the s
lay-up process, except
steps are as follows:
1. The mold is wax
2. The gel coat is ap
before building a
3. The barrier coat i
surface.
4. The barrier coat
5. Virgin resin is m
aluminum trihyd
h chops the glass rovings, is mounted on the spray-
of resin, catalyst, and chopped fiber glass is sprayed
a fan pattern. The method of mixing the resin
and
type of spraygun, as previously discussed. After each
rkers roll out the entire laminate. Increased attention
ers so that a smooth and even surface is obtained.
laminate is built up, corrugated material, foam, or
y parts as a core material to make it a sandwich
terial is applied to flat areas, bend areas, and the
part is then cured in an oven and brought to room
ng, a second skin or laminate is formed using the
me material is used during spray-up process to form
he part is again oven cured and brought to room
is removed and it is waxed and polished for the next
ne on the tub by trimming the edges and drilling
ab bars. Other secondary operations are performed
ments of the product. The part is then weighed for
es and inspected for dimensional tolerances, struc-
rface finish quality. Finally, the product is tagged for
d shipped to the warehouse.
pplying Heat and Pressure
s very economical because it does not have a high
e. The part is room-temperature cured or sometimes
production volume. No pressure is applied during
er spraying the resin and reinforcement, rollers are
rapped air as well as to create an even and smooth
ing Steps
pray-up process are almost the same as for the wet
for the method of creating the laminates. The basic
ed and polished for easy demolding.
plied to the mold surface and allowed to harden
ny other layer.
s applied to avoid fiber print through the gel coat
is oven cured.
ixed with fillers such as calcium carbonate or
rate and pumped to a holding tank.

6. Resin, catalyst, an
with the help of
a predetermined
7. A roller is used f
as well as to c
Entrapped air is
8. Where desirable,
into the laminate
9. The laminate is c
10. The part is demo
11. Quality control p
ances, structural
then approve or

6.8.3.7 Advantages o

The spray-up process o
1. It is a very econo
2. It utilizes low-co
3. It is suitable for

6.8.3.8 Limitations o

The following are some
1. It is not suitable f
ments.
2. It is difficult to
thickness. These
3. Because of its op
4. The process offe
surface finish on
5. The process is n
and process repe
does not provide
both or all the si

6.8.4 Filament Windi

Filament winding is a p
over a rotating mandre
process is shown in Fig
d chopped fibers are sprayed on the mold surface
a hand-held spraygun. The spraygun is moved in
pattern to create uniform thickness of the laminate.
or compaction of sprayed fiber and resin material
reate an even and smooth laminate surface.
removed.
wood, foam, or honeycomb cores are embedded
to create a sandwich structure.
ured in an oven.
lded and sent for finishing work.
ersonnel inspect the part for dimensional toler-
soundness, and good surface finish quality, and
reject the part, depending on its passing criteria.
f the Spray-Up Process
ffers the following advantages:
mical process for making small to large parts.
st tooling as well as low-cost material systems.
small- to medium-volume parts.
f the Spray-Up Process
of the limitations of the spray-up process:
or making parts that have high structural require-
control the fiber volume fraction as well as the
parameters highly depend on operator skill.
en mold nature, styrene emission is a concern.
rs a good surface finish on one side and a rough
the other side.
ot suitable for parts where dimensional accuracy
atability are prime concerns. The spray-up process
a good surface finish or dimensional control on
des of the product.
ng Process
rocess in which resin-impregnated fibers are wound
l at the desired angle. A typical filament winding
ures 6.29 and 6.30, in which a carriage unit moves

back and forth and the
the motion of the carria
generated. The process i
can be automated for m
Filament winding is the
certain specialized struc

6.8.4.1 Major Applic

The most common prod
tubular structures, pres
storage tanks, and roc
shown in Figure 6.31. T
machines and dedicated
to be produced and m
been overcome. Bent s

FIGURE 6.29

Schematic of the filament win

FIGURE 6.30

Demonstration of the filament
Fibers from
Resin bath
M
mandrel rotates at a specified speed. By controlling
ge unit and the mandrel, the desired fiber angle is
s very suitable for making tubular parts. The process
aking high-volume parts in a cost-effective manner.
only manufacturing technique suitable for making
tures, such as pressure vessels.
ations
ucts produced by the filament winding process are
sure vessels, pipes, rocket motor casings, chemical
ket launch tubes. Some filament wound parts are
he introduction of sophisticated filament winding
CAD systems has enabled more complex geometries
ding process.
winding operation. (Courtesy of Entec Composite Machines, Inc.)
Wound resin impregnated fibers
spool
Guide rail
Delivery point
andrel
any of the original geometric limitations have now
hapes, connecting rods, bottles, fishing rods, golf
© 2002 by CRC Press LLC
shafts, pressure rollers,
motive), oil field tubing,
hot sticks (non-conduc
handle bars, baseball/s
oars, tubes, etc. are curr
Filament wound glas
piping systems. It pro
wound pipe reduces th
35%, due to its smooth i
pipe. The weight of GR
that of concrete, and thu
installation of these pip
used for deep-water app
platform and riser syste
posite production riser’
riser systems lead to pla
requirements. High-pre
FIGURE 6.31
Filament wound parts. (Cour
bushings, bearings, driveshafts (industrial and auto-
cryogenics, telescopic poles, tool handles, fuse tubes,
ting poles), conduits, fuse lage, bicycle frames and
oftball bats, hockey sticks, fishing rods, ski poles,
ently produced using filament winding techniques.
s reinforced plastic (GRP) is used for water supply
vides clean and lead-free piping system. Filament
e pumping energy required to move water by 10 to
nterior surfaces compared to concrete or ductile iron
P pipe is one fourth that of ductile iron, one tenth
s provides added advantages in transportation and
es. Figure 6.32 shows a composite production riser
lications. It offers significant cost benefits to offshore
ms with no reduction in system reliability. The com-
s light weight and reduced stiffness relative to steel
tform size reduction and reduction of top tensioning
tesy of Advanced Composites, Inc.)
ssure composite accumulator bottles are shown in
© 2002 by CRC Press LLC
Figure 6.33. These bott
significant weight savin
6.8.4.2 Basic Raw M
In general, starting ma
(yarns) and liquid therm
rack and passed throug
wet as they pass throug
used for the filament w
because of its low cost
materials. Glass fibers
applications. Glass with
offshore applications. S
als. The use of prepreg
content throughout the
is also used for making
6.8.4.3 Tooling
The most common too
steel mandrel. Steel ma
get a high-gloss finish
well as to aid in easy r
FIGURE 6.32
Composite production riser
Composites.)
les are used in the offshore oil industry and offer
gs relative to steel bottles.
aterials
terials for filament winding are continuous fibers
oset resins. Yarns are kept in spool form at the back
h a resin bath located in the carriage unit. Fibers get
h the resin bath. Glass, carbon, and Kevlar fibers are
inding process but glass fibers are more common
. Epoxy, polyester, and vinylester are used as resin
with polyester resins are widely used for low-cost
epoxy is used n spoolable filament-wound tubes for
ometimes, prepreg tows are used as starting materi-
tows provides uniform fiber distribution and resin
thickness of the part. The filament winding process
preforms for the RTM process.
ling material for the filament winding process is a
ndrels
are chrome plated in certain applications to
made by the filament winding operation. (Courtesy of Lincoln
on the inside surface of the composite structure as
emoval of the mandrel. Aluminum is also used for
© 2002 by CRC Press LLC
making mandrels. For so
is not removed and beco
non-removal mandrel p
composite inner surface
inside the pressure vess
used as barrier materia
destructible/collapsible
and cardboard can be u
Cylindrical mandrels
manufacturing processe
diameter costs betwee
between $250 and $500
6.8.4.4 Making of th
To make filament wou
winding machine as sh
machine is similar to a
used to hold the mand
on the carriage unit. The
to the mandrel to lay do
Various types of comput
in the market, ranging f
FIGURE 6.33
Composite accumulator bottl
me applications, such as pressure vessels, the mandrel
mes an integral part of the composite structure. The
rovides an impermeable layer/barrier surface on the
and thus avoids leakage of compressed gas or liquid
el. Typically, metals and thermoplastic materials are
ls. Plaster of Paris and sand are also used to make
mandrels. For protyping purposes, wood, plastics,
sed.
are inexpensive compared to tooling costs for other
s. A 48- to 60-in.-long steel mandrel with a 1- to 2-in.
n $50 and $100. A chrome-plated mandrel costs
for the same size.
e Part
nd structures, a mandrel is place on the filament
own in Figures 6.29 and 6.30. A filament winding
lathe machine where the head and tail stocks are
rel and the cutting tool is replaced by a payout eye
mandrel rotates and the carriage unit moves relative
wn the resin-impregnated fibers at a specific angle.
er-operated filament winding machines are available
es. (Courtesy of Lincoln Composites.)
rom two-axes to six-axes filament winding machines.
© 2002 by CRC Press LLC
The carriage unit can m
these axes. In two-axes
the carriage unit moves
Before winding begins
a gel coat is applied on
quality on the interior su
it is placed between th
winding, fiber yarns, wh
through the resin bath
through the payout eye.
bundle must be remove
tem must facilitate the b
ingress. To achieve good
kept at constant tension
blade at resin bath is us
small, the laminate is no
on the laminate. If the te
starved areas near inside
off excess resin and crea
series of relative motion
the desired winding, the
pipe diameters, mandre
depending on the softwa
distribution, the mandre
area where the laminate
ature. For thick laminat
the laminate to cure bet
mandrel is extracted usin
is provided in the mand
To manufacture 28-in.
the filament winding pr
on the mandrel to get e
tions.8 Then, continuou
After the hoop wound l
FIGURE 6.34
Doctor blade arrangement in
Incoming rov
Docto
ove along the x, y, and z axes as well as rotate about
filament winding machines, the mandrel rotates and
back and forth only in one direction.
, the mandrel is coated with release agent. Sometimes,
the top of the release agent to get high surface finish
rface of the composite. Once the mandrel is prepared,
e head and tail stocks of the machine. During wet
ich are placed in spool form at the creels, are passed
located in the carriage unit and then to the mandrel
To achieve good fiber wet-out, air held inside the fiber
d and replaced with the resin. The impregnation sys-
reak-up of any film formers on the bundle for resin
impregnation, several things are done: rovings are
, rovings are passed through guided pins, a doctor
ed (Figure 6.34). If the tension on the rovings is too
t fully compacted and creates an excess resin region
nsion is too high, it can cause fiber breakage or resin-
layers. The use of a doctor blade arrangement scrapes
tes a uniform resin layer. Laminate is formed after a
s between the mandrel and the carriage unit. To get
machine operator inputs various parameters such as
l speed, pressure rating, band width, fiber angle, etc.,
re requirements. After creating the desired fiber angle
l with the composite laminate is removed to a curing
is cured at room temperature or at elevated temper-
es, it may be necessary to wind in stages and allow
ween winding operations. Once the part is cured, the
g an extracting device. Sometimes, a small taper angle
rel for easy removal of the composite part.
diameter GRP pipes for water piping systems using
ocess, first chopped rovings (2-in. length) is applied
qual properties in the axial and longitudinal direc-
s fibers are wound along 90° to get hoop strength.
the filament winding operation.
Impregnated
rovings
Pickup cylinder
ings
r blade
Resin bath
ayers, a 2-in. wide nonwoven fiberglass surface mat
© 2002 by CRC Press LLC
having a density of 30 g
40% by weight) is com
moved to a curing sta
infrared heating on the
of the steel band in the
are cut to a desired le
installation, the edges o
are then taken out for fi
6.8.4.5 Methods of A
The pressure during fil
In general, 1 lbf to 6 lbf
or by passing the fibers
tension. Composites thu
oven at a higher tempe
part fabrication is autom
with the mandrel is m
slowly moves in the hea
of the composite part. T
where the mandrel is
machine for winding p
Ultraviolet (UV) curin
during the filament wind
for curing the resin in b
the low end of the radia
volt (eV) range; where
1 million eV range. To fa
added to the resin form
sensitive to radiation en
cury/vapor bulb is used
the curing action. Once
photoinitiator breaks do
chemical bond sites wit
other free radicals, the s
mix to polymerize into
cannot be used for curin
turing processes becaus
cured. Moreover, it cann
colored material, such
focused on continuous p
The outer surface fin
good and requires extr
create a good outer fini
is complete or a teflon-c
absorb excess resin.
/m2 is applied. Orthophthalic polyester resin (30 to
monly used to make GRP pipes. The pipe is then
tion where it is cured at about 250 to 265°F using
outer layers of the laminate and induction heating
inside layers of the composites. After curing, pipes
ngth using a computer-controlled saw. For ease of
f the pipe are chamfered to a 30° angle. The pipes
nishing and pressure testing.
pplying Heat and Pressure
ament winding is applied by creating fiber tension.
fiber tension is created using some tensioning device
through the carriage unit in such a way that it creates
s fabricated are cured at room temperature, or in an
rature. For large-volume production, the process of
ated. In an automated line, the filament wound part
oved to a heated chamber using a robot. The part
ted chamber and comes out after partial or full cure
he part is then sent to the mandrel extracting station
extracted and sent back to the filament winding
urposes. All of this can be done automatically.
g as well as electron beam curing are also performed
ing process to cure the resin. Radiation energy is used
oth UV and electron beam curing. UV radiation is at
tion spectrum, releasing energy in the 1.7 to 6 electron
as in electron beam radiation, it is in the 10,000 to
cilitate UV curing, an additive such as Accuset 303 is
ulation. The additive contains a photoinitiator that is
ergy. A light source such as an electrode-based mer-
to deliver the correct UV wavelength energy to initiate
exposed to the UV rays, the chemical structure of the
wn into energized free radicals that actively seek new
hin the resin mix. When the free radicals bond with
ize of the polymer chain increases, causing the resin
the solid state. UV curing has the drawback that it
g of laminates produced by other composite manufac-
e UV rays must “see” the material that needs to be
ot penetrate beneath the top layer of pigmented or
as black carbon fiber. For this reason, UV curing is
rocessing of materials such as filament winding.
ish quality of filament wound parts is usually not
a machining and
sanding of the outer surface. To
sh, the part is sometimes shrink taped after winding
oated air breather is applied on the outer surface to
© 2002 by CRC Press LLC
6.8.4.6 Methods of G
The desired fiber archi
relative motion of the m
winding motions can b
tion. Sometimes, the su
application programs f
cylinders, bottles, and
motions are determined
a desired trajectory of fi
then the mandrel and c
error so that fiber filam
and thus the motion of
times, interactive graph
the stored data.10,11 Onc
culated, these data are g
in-programming is still
be determined by simu
The latest technology
winding machines with
ports.12,13 The equipmen
of several servo axes, a
The winding motion is
using a floppy disk. M
simulate the winding p
data to the computer th
CAD/CAM systems
which integrate a three-
ing software, and desig
used to model compone
by performing stress an
path is known, the filam
by defining successive
point. The ends of thes
the mandrel frame of r
applied to check for pos
circuit is generated, deli
frame of reference to a c
of the filament winding
these data into the five
machine. Machine moti
such a way that the ne
match with the desired
motion by this techniqu
ticated filament winding
enerating the Desired Winding Angle
tecture of the mandrel surface is generated by the
andrel and payout eye. There are several ways that
e determined to get the desired fiber angle distribu-
ppliers of the filament winding machine provide
or the winding of standard shapes such as rings,
pressure vessels. In another approach, the winding
by the teach-in-programming technique, in which
ber path is first marked on the mandrel surface and
arriage units are incrementally moved by trial and
ents are laid on the marked trajectory.9 Coordinates
the mandrel and carriage units are recorded. Some-
ics packages are used for smoothing and editing of
e the required data for one complete stroke are cal-
enerally repeated after indexing the mandrel. Teach-
used in some places. Delivery point motion can also
lation of the filament winding process.10
offers new-generation computer-controlled filament
floppy disk and hard disk drives and RS 232 input
t is configured such that it relies on real-time control
nalog and digital outputs, and tension controllers.
generated from data transferred from other sources
anufacturing engineers use computer graphics to
attern, record the data, and then feed the resulting
rough a line or floppy disk.
have also been developed for filament winding,14,15
dimensional surface modeler, specific filament wind-
n software. A three-dimensional surface modeler is
nt geometries and to determine the fiber orientation
alysis and using failure criteria. Once the winding
ent winding software simulates the winding process
straight lines tangential to the winding path at each
e straight lines define the path of delivery point in
eference. At this stage, an intersection calculation is
sible regions of collision. Once an acceptable winding
very point locations are converted from the mandrel
oordinate system that corresponds to the kinematics
machine. The most difficult task here is to convert
or six simultaneous axes of the filament winding
on for each degree of freedom is then determined in
t effect of motion of each degree of freedom should
movement of the delivery point location. Machine
e is sometimes quite complex and requires a sophis-
machine with a large number of degrees of freedom.
© 2002 by CRC Press LLC
Robots have also been
shaped structures.16,17 In
(computer numerical co
ery point is obtained d
mandrel surface.17 In th
delivery point and the
moves on the mandrel
because the distance be
not zero, the accuracy o
filament winding mach
the robot arm from pe
mandrel or other objec
the robot arm, and mac
Mazumdar and Hoa1
determine the mandrel
angle distributions on c
isymmetric mandrel sh
in which geometrical a
the winding motion. Us
machine having two de
angle on cylindrical, n
shapes. For some cylin
as rectangular or hexag
culations without the u
For cylinders with poly
is 100% accurate. For
program is developed t
for the desired winding
6.8.4.7 Basic Process
To more easily underst
during the filament wi
common in all wet filam
1. Spools of fiber y
2. Several yarns fro
pins to the payou
3. Hardener and re
poured into the r
4. Release agent an
drel surface and
stocks of the fila
5. Resin-impregnat
placed at the sta
is created using
introduced into filament winding of small, complex-
many cases of robotic filament winding and CNC
ntrolled) filament winding, the motion of the deliv-
irectly from the stable fiber path predictions on the
is case, it is assumed that the distance between the
mandrel surface is zero and that the delivery point
surface along the desired fiber trajectory. In fact,
tween the delivery point and the mandrel surface is
f fiber placement is less than that offered by regular
ines.17 Other possible restrictions that might prevent
rforming its prescribed task are collisions with the
ts, singularity positions or joint angle limitations of
hine dynamics.16,17
8-23 have developed a series of kinematic models to
and carriage motions for generating desired fiber
ylindrical, noncylindrical, axisymmetric, and nonax-
apes. Their method relies on a geometric approach
nd trigonometrical relations are used to determine
ing their model, a simplest form of filament winding
grees of freedom can generate the desired winding
oncylindrical, axisymmetric, and nonaxisymmetric
drical mandrels with polygonal cross-sections such
onal, the method requires some simple manual cal-
se of a computer to determine the winding motion.
gonal cross-sections, the winding motion prediction
mandrels with curved surfaces, a small computer
o determine the mandrel and carriage unit velocities
angle.
ing Steps
and the entire process, the major steps performed
nding process are described here. These steps are
ent winding processes.
arns are kept on the creels.
m spools are taken and passed through guided
t eye.
sin systems are mixed in a container and then
esin bath.
d gel coat (if applicable) are applied on the man-
the mandrel is placed between the head and tail
ment winding machine.
ed fibers are pulled from the payout eye and then
rting point on the mandrel surface. Fiber tension
a tensioning device.
© 2002 by CRC Press LLC
6. The mandrel and
system in the ma
fiber architecture
7. Fiber bands are
builds up as the
8. To obtain a smo
coated bleeder o
after winding is
9. The mandrel wit
chamber where
elevated tempera
10. After curing, the
then reused. For
and it becomes a
6.8.4.8 Advantages o
Filament winding has g
capability in laying dow
Filament winding offer
FIGURE 6.35
Demonstration of fiber laydo
payout eye motions are started. The computer
chine creates winding motions to get the desired
in the laminate system, as shown in Figure 6.35.
laid down on the mandrel surface. The thickness
winding progresses.
oth surface finish on the outer surface, a teflon-
r shrink tape is rolled on top of the outer layer
completed.
h the composite laminate is moved to a separate
the composite is cured at room temperature or
ture.
mandrel is extracted from the composite part and
certain applications, the mandrel is not removed
n integral part of the composite structure.
f the Filament Winding Process
ained significant commercial importance due to its
wn on a mandrel. (Courtesy of Lincoln Composites.)
n the fibers at a precise angle on the mandrel surface.
s the following advantages.
© 2002 by CRC Press LLC
1. For certain appl
filament winding
effective and hig
2. Filament windin
cost tooling to m
3. Filament windin
volume composi
6.8.4.9 Limitations o
Filament winding is hig
ever,
the process has th
1. It is limited to p
suitable for mak
applications, fila
such as leaf sprin
two halves and t
2. Not all fiber ang
ing process. In g
bility. Low fiber
3. The maximum fi
is only 60%.
4. During the filam
form fiber distrib
of the laminate.
6.8.5 Pultrusion Proc
The pultrusion process
which resin-impregnate
The process is similar
being that instead of ma
process, it is pulled thro
parts of constant cross-
Pultrusion is a simp
Figure 6.36 illustrates a t
yarns are pulled through
through the heated die,
yields smooth finished p
6.8.5.1 Major Applic
Pultrusion is used to fa
with constant cross-sec
ications such as pressure vessels and fuel tanks,
is the only method that can be used to make cost-
h-performance composite parts.
g utilizes low-cost raw material systems and low-
ake cost-effective composite parts.
g can be automated for the production of high-
te parts.
f the Filament Winding Process
hly suitable for making simple hollow shapes. How-
e following limitations.
roducing closed and convex structures. It is not
ing open structures such as bathtubs. In some
ment winding is used to make open structures
gs, where the filament wound laminate is cut into
hen compression molded.
les are easily produced during the filament wind-
eneral, a geodesic path is preferred for fiber sta-
angles (0 to 15°) are not easily produced.
ber volume fraction attainable during this process
ent winding process, it is difficult to obtain uni-
ution and resin content throughout the thickness
ess
is a low-cost, high-volume manufacturing process in
d fibers are pulled through a die to make the part.
to the metal extrusion process, with the difference
terial being pushed through the die in the extrusion
ugh the die in a pultrusion process. Pultrusion creates
section and continuous length.
le, low-cost, continuous, and automatic process.
ypical pultrusion process in which resin-impregnated
a heated die at constant speed. As the material passes
it becomes partially or completely cured. Pultrusion
arts that usually do not require post-processing.
ations
bricate a wide range of solid and hollow structures
tions. It can also be used to make custom-tailored
© 2002 by CRC Press LLC
parts for specific applica
beams, channels, tubes
walkways and bridges,
etc. Typical pultruded
are used in infrastruct
sectors. Figure 6.38 sho
are lightweight, longlas
fiberglass covers for hig
in Figure 6.39, and roll
sidewall panels are sh
fiberglass stair system
platform. Pultruded pa
FIGURE 6.36
Illustration of a pultrusion pr
FIGURE 6.37
Typical pultruded shapes. (C
Roving creels
Gu
tions. The most common applications are in making
, grating systems, flooring and equipment support,
handrails, ladders, light poles, electrical enclosures,
shapes are shown in Figure 6.37. Pultruded shapes
ure, automotive, commercial, and other industrial
ws a fiberglass grating system. The grating systems
ting, and provide easy installation. Nonconductive
h-voltage rails for a rapid transit system are shown
-up fiberglass trailer doors and Z-bar separators in
own in Figure 6.40. Figure 6.41 shows a complete
ocess.
ourtesy of GDP, France.)
Mat creels
ide Resin
bath
Heated
die
Pulling
unit
Inspection
and
packing
Cut off
saw
having structural members, railings, treads, and a
rts are used in the above applications.
© 2002 by CRC Press LLC
6.8.5.2 Basic Raw M
Pultrusion is typically
E-glass, S-glass, carbon
most common type bein
add bidirectional and
polyester is the most c
Pultrusion offers an at
processing. Vinylesters
the processing of these r
with these resins are lo
FIGURE 6.38
Fiberglass grating and handr
sions, Inc.)
aterials
used for making parts with unidirectional fibers.
, and aramid fibers are used as reinforcements, the
g E-glass rovings. Fabrics and mats are also used to
multidirectional strength properties. Unsaturated
ommon resin material for the pultrusion process.
tractive performance-to-price ratio as well as easy
and epoxies can be used for improved properties but
esins becomes difficult. Moreover, the pulling speeds
ail systems using pultruded parts. (Courtesy of Creative Pultru-
wer because of lower resin reactivity.
© 2002 by CRC Press LLC
Various types of fille
insulation characteristi
lower the overall cost. C
pultruded part. Calcium
major filler in SMC com
part. Alumina trihydrat
Aluminum silicate (kao
face finish, and chemica
FIGURE 6.39
Nonconductive fiberglass cov
Creative Pultrusions, Inc.)
FIGURE 6.40
Lightweight roll-up fiberglass
of Creative Pultrusions, Inc.)
rs are added to the polyester resin to improve the
cs, chemical resistance, and fire resistance, and to
alcium cabonates are added to lower the cost of the
carbonate is a very inexpensive material and is a
pounds. It improves the whiteness (opacity) of the
e and antimony trioxide are used for fire retardancy.
lin clay) provides enhanced insulation, opacity, sur-
ers for high-voltage rails on a rapid transit system. (Courtesy of
trailer doors and Z-bar separators in sidewall panels. (Courtesy
l resistance.
© 2002 by CRC Press LLC
6.8.5.3 Tooling
For the pultrusion proc
nated fibers to the desi
their length, except for
are heated to a specific
Tooling costs depend up
requirement. The cost o
on the size and cross-se
of 150,000 linear feet be
re-chromed to minimiz
750,000 linear feet until
Dies are segmented
chrome plating. At the
lines) are created on the
raised line on the surfa
6.8.5.4 Making of th
To make composite par
placed on the creel sim
forcements are passed
with the resin. There are
rovings are passed thro
reinforcement can pass
down through a guid
when bending is avoide
FIGURE 6.41
All-fiberglass stair systems ha
of Creative Pultrusions, Inc.)
ess, steel dies are used to transform resin-impreg-
red shape. Dies have a constant cross-section along
some tapering at the raw material entrance. The dies
temperature for partial or complete cure of the resin.
on the complexity of the part as well as the volume
f the die ranges from $4000 to $25,000, depending
ction of the part. Tooling life is generally in excess
fore major re-work is required. Tools are frequently
e destructive wearing. The total life could go up to
further re-work in the die becomes impractical.
for easy assembly, disassembly, machining, and
joining of these segments, surface marks (parting
pultruded part. A parting line appears as a slightly
ce.
e Part
ts using the pultrusion process, spools of rovings are
ilar to the filament winding process and then rein-
through a resin bath where fibers are impregnated
two major impregnation options. In the first option,
ugh an open resin bath, as shown in Figure 6.36. The
horizontally inside the bath (Figure 6.36) or up and
ing mechanism. Reinforcements pass horizontally
ving structural members, railings, treads, and platform. (Courtesy
d. Fabrics and mats are usually passed horizontally.
© 2002 by CRC Press LLC
Open resin bath impreg
simplicity. In this meth
the second option, rein
injected under pressure.
a tapered cavity for imp
minimum styrene emiss
expensive dies. Once the
tive to friction and can b
guides are used because
thus impregnated are pa
at the entrance and a co
and solidifies as it passes
on resin reactivity, par
higher the resin reactivi
The solidified materi
clamp pullers. These pu
the composite material.
that the composite mate
Pultrusion provides
automated nature of th
compared to prepregs a
tinuous process, literall
duced are cut to predet
hacksaw. The length of
on the order of 10 m. I
length requirements.
Following are some of
ing pultruded parts.
6.8.5.4.1 Wall Thicknes
Wherever possible, sele
provides uniform coolin
ual stress and distortion
vide uniform shrinkage
product. Typically, 2 to
maintain symmetry in t
For high-volume pro
the curing time and the
part. For example, a 0.7
approximately 9 in./mi
a production rate of 3 to
in the part, then it can b
wall or by including ri
between selecting a thic
production rate, lower
nation is the most common method because of its
od, impregnation takes place by capillary action. In
forcement passes through a cavity where resin is
This system utilizes a different kind of die, which has
regnation. The advantages of this method are no or
ion and low resin loss. However, this method requires
reinforcement becomes impregnated, it is less sensi-
e guided using sheet-metal guides. In general ceramic
of the abrasive nature of dry fibers. Reinforcements
ssed through a heated die. The die has a slight taper
nstant cross-section along its length. The resin cures
through the heated die. The length of the die depends
t thickness, and production rate requirements. The
ty, the shorter the die length requirement.
al is pulled by caterpillar belt pullers or hydraulic
llers are mounted with rubber-coated pads that grip
The puller is distanced from the die in such a way
rial cools off enough to be gripped by the rubber pads.
lowest cost composite parts because of the highly
e process as well as lower fiber and resin costs as
nd fabrics. Because the pultrusion process is a con-
y any length can be produced. However, parts pro-
ermined lengths using an automatic saw or manual
the pultrusion facility from creel to saw is typically
t can be longer, depending on part complexity and
the considerations while manufacturing and design-
s
ct uniform thickness in the cross-section because it
g and curing, and thus avoids the potential of resid-
s in the part. Moreover, uniform thickness will pro-
in the part and thus will limit the warpage in the
3% shrinkage occurs in the pultruded part. Also,
he cross section for minimal distortion.
duction, the thickness of the part is critical because
refore the rate of pull depend on the thickness of the
5-in. thick cross-section can be produced at a rate of
n, whereas a 0.125-in. thick cross-section can provide
4 ft/min. Therefore, if a design requires high rigidity
e achieved by creating deeper sections with thinner
bs in the cross-section. Similarly, if there is a choice
k rod or tube, select the tube because it offers a higher
cost, and higher specific strength.
© 2002 by CRC Press LLC
6.8.5.4.2 Corner Design
In a pultruded part, avo
corners. Generous rad
improve the strength by
minimum of 0.0625-in.
Another important co
uniform thickness arou
rich areas, which can cr
ness will provide unifo
obtaining consistent pa
6.8.5.4.3 Tolerances, Fla
Dimensional tolerances
parts should be discuss
glass pultruded profiles
mittees. Refer to ASTM
standard specifications
terms relating to pultru
Pultrusion is a low-p
tolerances in the part. S
tolerances, flatness, and
The cost of a product
Tight tolerance implies
provide generous tolera
product is not affected.
6.8.5.4.4 Surface Textur
Pultrusion is a low-pres
face. This can cause patt
easily exposed under w
fiber mats are used as
good UV and outdoor e
of polyurethane coating
6.8.5.5 Methods of A
During pultrusion, ther
dation. Therefore, this p
impregnated rovings or
the die, gets compacted
and applies heat to inco
cures the resin. The par
before it is gripped by
id sharp corners and provide generous radii at those
ii offer better material flow at corners as well as
distributing stress uniformly around the corner. A
radius is recommended at corners.
nsideration in the design of corners is to maintain
nd the corner. This will avoid the build-up of resin-
ack or flake off during use. Moreover, uniform thick-
rmity in fiber volume fraction and thus will help in
rt properties.
tness, and Straightness
, flatness, and straightness obtained in pultruded
ed with the supplier. Standard tolerances on fiber-
have been established by industry and ASTM com-
3647-78, ASTM D 3917-80, and ASTM D 3918-80 for
on dimensional tolerances and definitions of various
ded products.
ressure process and therefore does not offer tight
hrinkage is another contributing factor that affects
straightness.
is significantly affected by tolerance requirements.
higher product cost. Therefore, whenever possible,
nces on the part as long as the functionality of the
e
sure process and typically provides a fiber-rich sur-
ern-through of reinforcing materials or fibers getting
ear or weathering conditions. Surfacing veils or finer
an outer layer to minimize this problem. To create
xposure resistance, a 0.001- to 0.0015-in. thick layer
is applied as a secondary operation.
pplying Heat and Pressure
e is no external source to apply presure for consoli-
rocess is known as a low-pressure process. The resin-
mat, when passed through a restricted passage of
and consolidated. The die is heated to a temperature
ming material for desired cure. The heat in the die
t coming out of the die is hot and is allowed to cool
the puller.
© 2002 by CRC Press LLC
6.8.5.6 Basic Process
The major steps perform
These steps are commo
1. Spools of fiber y
2. Several fiber yar
the resin bath.
3. Hardener and re
poured in the res
4. The die is heated
5. Resin-impregnat
the die, where re
6. The pultruded p
7. The surface is p
important eleme
pultrusion proce
releases are a for
the part. This film
sandblasting. So
preparation. Seve
ride, or acetone)
6.8.5.7 Advantages o
Pultrusion is an automa
1. It is a continuous
the finished part
parts. Typical pr
2. It utilizes low-co
duction of low-c
6.8.5.8 Limitations o
Pultruded components
and consumer products
has the following limita
1. It is suitable for p
length. Tapered a
2. Very high-tolera
cannot be produ
3. Thin wall parts c
ing Steps
ed during the pultrusion process are described here.
n in most pultrusion processes:
arns are kept on creels.
ns from the spool are taken and passed through
sin systems are mixed in a container and then
in bath.
to a specified temperature for the cure of resin.
ed fibers are then pulled at constant speed from
sin gets compacted and solidified.
art is then cut to the desired length.
repared for painting. Surface preparation is an
nt to perform finishing operations because the
ss utilizes internal mold releases. These mold
m of wax that form a film on the outer surface of
can be removed by solvent wiping, sanding, or
lvent wiping is the simplest method of surface
ral solvents (e.g., toluene, xylene, methylene chlo-
can be used for this purpose.
f the Pultrusion Process
ted process with the following advantages:
process and can be compeletely automated to get
. It is suitable for making high-volume composite
oduction speeds are 2 to 10 ft/min.
st fiber and resin systems and thus provides pro-
ost commercial products.
f the Pultrusion Process
are used on a large scale in infrastructure, building,
because of lower product cost. However, pultrusion
tions.
arts that have constant cross-sections along their
nd complex shapes cannot be produced.
nce parts on the inside and outside dimensions
ced using the pultrusion process.
annot be produced.
© 2002 by CRC Press LLC
4. Fiber angles on p
to get bidirection
5. Structures requir
this process beca
direction.
6.8.6 Resin Transfer M
The resin transfer mold
molding process. Altho
processes have gained p
use is mostly limited t
molding compounds (s
processes, the RTM pr
parts in medium-volum
fabrication of near-net-s
Continuous fibers are u
In the RTM process, a
mold half is mated to th
using dispensing equipm
lyst, color, filler, etc., is p
in the mold. After curing
mixture, the
part is then
production of structural
The main issues in the
in porous media. The pr
resin under pressure in
preform. During mold fi
exothermic curing react
finally solidification. A
resin, cure reactions cont
The RTM process is a
is placed inside a mold
inlet port until the mold
part is removed from th
6.8.6.1 Major Applic
The RTM process is su
small- to medium-volum
sporting goods, and con
made are helmets, doo
sports car bodies, autom
tures made by the RTM
ribs and stiffeners, fairi
ultruded parts are limited to 0°. Fabrics are used
al properties.
ing complex loading cannot be produced using
use the properties are mostly limited to the axial
olding Process
ing (RTM) process is also known as a liquid transfer
ugh injection molding and compression molding
opularity as high-volume production methods, their
o nonstructural applications because of the use of
hort fiber composites). In contrast to these molding
ocess offers production of cost-effective structural
e quantities using low-cost tooling. RTM offers the
hape complex parts with controlled fiber directions.
sually used in the RTM process.
preform is placed into the mold cavity. A matching
e first half and the two are clamped together. Then,
ent, a pressurized mixture of thermoset resin, a cata-
umped into the mold using single or multiple ports
for 6 to 30 min, depending on the cure kinetics of the
removed from the mold. Thus, RTM results in the
parts with good surface finish on both sides of the part.
RTM process are resin flow, curing, and heat transfer
ocess involves injecting a precatalyzed thermosetting
to a heated mold cavity that contains a porous fiber
lling, the resin flows into the mold and experiences
ions, causing its viscosity to increase over time and
fter the fiber preform is completely saturated with
inue past the gel-point to form a cross-linked polymer.
closed mold operation in which a dry fiber preform
and then the thermoset resin is injected through an
is filled with resin. The resin is then cured and the
e mold.
ations
itable for making small- to large-sized structures in
e quantities. RTM is used in automotive, aerospace,
sumer product applications. The structures typically
rs, hockey sticks, bicycle frames, windmill blades,
otive panels, and aircraft parts. Some aircraft struc-
process include spars, bulkheads, control surface
ngs, and spacer blocks.
© 2002 by CRC Press LLC
Figure 6.42 shows a br
dal hub for satellite app
components are shown
medium-sized, precisio
FIGURE 6.42
Braided and resin transfer m
tesy of Fiber Innovation, Inc.
FIGURE 6.43
Resin transfer molded aerosp
aided and resin transfer molded carbon/epoxy toroi-
lication. Some of the resin transfer molded aerospace
in Figure 6.43. Figure 6.44 shows typical small- to
olded carbon/epoxy toroidal hub for satellite application. (Cour-
)
ace components. (Courtesy of Intellitec.)
n reinforced resin transfer molded parts. Figure 6.45
© 2002 by CRC Press LLC
shows a one-piece carbo
monocoque frame does
Figure 6.46 shows a com
electroformed nickel fa
FIGURE 6.44
Typical small- to medium-size
FIGURE 6.45
One-piece monocoque bicycle
n fiber bicycle frame made by the RTM process. The
not use metallic joints to connect the various tubes.
d resin transfer molded parts. (Courtesy of Liquid Control Corp.)
frame. (Courtesy of Radius Engineering, Inc.)
posite fork for the bicycle. The fork molds use an
ce. The structural backing material is formulated to
© 2002 by CRC Press LLC
match the coefficient o
high thermal conductiv
vide extremely rapid t
temperature rise at the
overshoot. Water coolin
high-temperature hold.
process control system.
6.8.6.2 Basic Raw M
For the RTM process, fi
There are several types
mats, and braided prefo
mats are produced by m
a moving carrier film o
a thermoplastic polyme
the desired size and fo
mold. In this process, s
because complicated th
flat mat and then formin
the preform maintains
strand mats are placed
placed as core material.
mats. Spun material is p
region in the inside reg
mandrel to obtain a th
FIGURE 6.46
Composite fork for the bicycl
f thermal expansion of the nickel face and provide
ity. Integral electrical heating and water cooling pro-
hermal cycling. Air cooling is used to control the
end of the rapid heat-up to prevent temperature
g is used to obtain rapid cool-down at the end of the
The molds operate in a shuttle press with an integral
aterials
ber preforms or fabrics are used as reinforcements.
of preforms (e.g., thermoformable mat, conformal
rms) used in the RTM process. The thermoformable
ore or less randomly swirling continuous yarns onto
r belt and then applying a binder, which is typically
r, to loosely hold the mat together. The mat is cut to
rmed under heat and pressure to the shape of the
craps are produced to get the final shape preform
ree-dimensional shapes are produced by cutting the
g it under heat and pressure. Once a shape is formed,
its shape. In conformal mats, fabrics or chopped
on the outer layer and spun-bonded core material is
These layers are stitched together to form conformal
laced as a core material to create a low-permeability
e. (Courtesy of Radius Engineering, Inc.)
ion. In braided preforms, fibers are woven over a
ree-dimensional fiber architecture. For low-volume
© 2002 by CRC Press LLC
applications, weaves, b
applications, random fi
used as reinforcing fibe
mon. Various methods
A wide range of resin
epoxy, phenolic, and me
ers including alumina tr
resins used for the RTM
with carbon fiber is ve
epoxies and other high
meter and condition the
developed to provide fa
Filler may be added to
of adding filler is to low
filler is only $0.05/lb, w
loons can also be used
$4/lb. Microballoons ar
1 lb of microballoon can
be cheaper. When mixi
with the resin, precautio
10 µm. A larger filler siz
size of 5 to 8 µm is reco
without any problem in
resin increases the visc
also significantly increa
be 30%, but the volume
6.8.6.3 Tooling
The RTM process prov
system as compared to
pression molding, the r
process is low compare
injection molding proce
heavy. At the same tim
investment for prototyp
of RTM compared to fil
processes is that the clos
environment, a factor o
gent regulations concer
The mold for the RTM
but for prototype purpo
the mold for making c
molds for making snow
shows a mold used to m
for the RTM process. Th
raids, and mats are utilized; and for high-volume
ber preforms are used. Glass, carbon, and Kevlar are
rs to make the preform, E-glass being the most com-
of making preforms are discussed in Chapter 2.
systems can be used, including polyester, vinylester,
thylmethacrylate, combined with pigments and fill-
ihydrate and calcium carbonates. The most common
process is unsaturated polyester and epoxies. Epoxy
ry common in the aerospace industry. The use of
-viscosity resins requires changes in equipment to
resin prior to injection. New epoxy resins are being
st cure, thus increasing the production rate.
the resin during the RTM process. The main purpose
er the cost of the part. The cost of calcium carbonate
hereas epoxy resin costs about $2 to $10/lb. Microbal-
as filler material but costs range between $3 and
e expensive on a weight basis but on a volume basis,
replace 100 lb of filler material and can turn out to
ng filler material such as ground calcium carbonate
ns are taken to ensure that filler size does not exceed
e creates a filtering problem with preforms. A filler
mmended so that the filler can move with the resin
side the fiber architecture. Mixing the filler with the
osity of the resin and slows the production rate. It
ses the weight of the part. The weight increase may
increase may be only 12% by adding the filler.
ides the advantage of utilizing
a low-cost tooling
other molding processes such as injection and com-
eason being that the pressure used during the RTM
d to the pressure requirements of compression and
sses. Because of this, tooling need not be strong and
e, low-cost tooling provides benefits of low initial
e building and for production run. Another benefit
ament winding, pultrusion, and other open molding
ed nature of the RTM process provides a better work
f growing importance in light of increasingly strin-
ning styrene emissions.
process is typically made of aluminum and steel
ses plastic and wood are also used. Figure 6.46 shows
omposite forks, whereas Figures 6.5 and 6.6 show
boards and tennis racquets, respectively. Figure 6.47
ake complicated parts, such as shown in Figure 6.48
e mold is generally in two halves containing single
© 2002 by CRC Press LLC
or multiple inlet ports f
and resin outlet. The de
in Section 6.4.3. The mo
FIGURE 6.47
Match molds. (Courtesy of G
FIGURE 6.48
Resin transfer molded part. (
or resin injection and single or multiple vents for air
KN Aerospace.)
Courtesy of GKN Aerospace.)
sign of the inlet port and vent locations is discussed
ld design is stiffness critical. The wall thickness of
© 2002 by CRC Press LLC
the mold should be suf
processing. The mold d
thermal considerations.
rials affect the dimensio
coefficients of thermal e
while designing the mo
be clamped and sealed
The cost of molds for p
depending on the comp
or to study resin flow b
$200 to $5,000. Transpa
resin flow behavior and
6.8.6.4 Making of th
In the RTM process, a p
in the cavity of a match
are inserted into the pre
used as core materials.
because the open surfa
resin flow inside the co
plex shapes is challengi
pylene cores that have s
the core and can be use
makes the structure ligh
tion. The purpose of pu
the structure. Once the
cavity, then the mold is
pneumatic presses or b
press is shown in Figure
RTM process is shown i
FIGURE 6.49
Schematics of the RTM proce
Clampin
force
Foa
ficiently rigid to take all the pressure exerted during
esign should also take into account handling and
Thermal properties of the mold and composite mate-
nal tolerances of the finished part and therefore the
xpansion for the mold and part need to be considered
ld. The tool should be designed to ensure that it can
properly.
roduction runs falls in the range of $2,000 to $50,000,
lexity and size of the part. To make prototype parts
ehavior, the cost of a mold can fall in the range of
rent materials such as acrylic are used for studying
other characteristics during processing.
e Part
reform of dry fiberglass mat or fabric is positioned
ed mold as shown in Figure 6.49. Cores and inserts
form as required. Typically, balsa and foam cores are
Honeycomb cores are not used in the RTM process
ce of the honeycomb material does not restrict the
re. Moreover, cutting the honeycomb core into com-
ng. There are some commercially available polypro-
urfacing veils, which restrict the flow of resin inside
d in the RTM process. Insertion of the core material
tweight and strong by creating a sandwich construc-
tting inserts is to create a fastening mechanism in
reinforcing and core materials are placed into the
closed. The mold can be closed using hydraulic or
y using clamps along the edges. A RTM molding
ss.
Resin
g Pressurized air
Preform
m core Mold halves
6.50. A typical production flow diagram during the
n Figure 6.51. It shows the sequence of material flow
FIGURE 6.50
RTM molding press. (Courtesy of Radius
© 2002 by CRC Press LLC
Engineering, Inc.)
FIGURE 6.51
A typical production flow diagram
© 2002 by CRC Press LLC
during the RTM process. (Courtesy of Radius Engineering, Inc.)
© 2002 by CRC Press LLC
from preform making to
aluminum mold for ma
aluminum mandrels, wh
fabric is wrapped arou
ends of the mandrels a
and left sides of the man
during the injection pro
aluminum and become
with end blocks and ma
is closed. The flap made
the inboard flap (right
shown with spoilers at
extreme left of the figu
the back of the flaps.
After closing the mo
pressure into the mold
dispensing equipment
dispensing equipment
ciently and accurately m
to hundreds of pounds
designed to handle poly
two-component resin sy
catalyst are stored in ta
before injection. In the
lated resin is stored in
inject the resin into the
ports are used for resi
typically used. For lon
uniform resin distributi
FIGURE 6.52
Molds and mandrels for mak
final part fabrication. Figure 6.52 shows an anodized
king aircraft flaps. The bottom of Figure 6.52 shows
ich are used to create internal ribs in the flap. Carbon
nd these mandrels and placed inside the mold. The
re placed inside the end blocks shown on the right
drels to make sure that these mandrels do not move
cess. Mandrels, end blocks, and molds are made of
black because of anodization. The reinforcements
ndrels are then placed inside the mold and the mold
by this mold is shown in Figure 6.53. In Figure 6.53,
-hand side) and outboard flap (left-hand side) are
the front of these flaps. The trim tab is shown at the
re. The press, which made these flaps, is shown at
ld, liquid resin is pumped under low to moderate
cavity using dispensing equipment. Custom-built
is available on the market for RTM purposes. RTM
is shown in Figure 6.54. The RTM machine can effi-
eter, mix, and inject materials, from a few ounces
, into low-pressure closed tools. The machines are
esters, methacrylates, epoxies, urethanes, and other
stems. In a typical dispensing equipment, resin and
nks A and B and mixed through a static mixer just
simplest form of dispensing equipment, preformu-
a pressure pot and then pressurized air is used to
mold as shown in Figure 6.49. Single or multiple
n injection. For small components, a single port is
ing aircraft flaps. (Courtesy of Radius Engineering, Inc.)
g and large structures, multiple ports are used for
on as well as for faster process cycle time. In general,
© 2002 by CRC Press LLC
FIGURE 6.53
Outboard and inboard aircra
Inc.)
FIGURE 6.54
RTM dispensing equipment.
ft flaps, spoilers, and trim tabs. (Courtesy of Radius Engineering,
(Courtesy of Liquid Control Corp.)
© 2002 by CRC Press LLC
the resin is injected at th
gravity to minimize ent
mold.
In an RTM process, r
within the RTM mold is
tion pressure, vacuum i
permeabilities. Preform
architecture, fiber volum
other factors. During m
tance and experiences
and reinforcing fibers.
Various computer mo
and visualize resin flow
the mold design phase
vents and optimal injec
inlet pressure and fill tim
spots. These models typ
law and finite element a
Because of the two-dim
simple geometries with
Dry spots (or improp
process. Dry spots in a
fore are directly related
avoid dry spots, vacuu
within the reinforceme
filling is achieved rapid
is completely filled with
ing. For unsaturated po
temperature, whereas
curing, the vent is close
ports until the resin ge
the part is removed.
6.8.6.5 Methods of A
The pressure during th
injection pressure. This
mold through porous m
equipment has a compr
the injection pressure is
The injection pressure
mold filling time. Afte
pressure in the mold d
injection pressure depen
porous media, mold fill
viscosity for RTM proce
e lowest point of the mold and flows upward against
rapped air. Vents are located at highest point of the
esin flow and fiber wet-out are critical. Resin flow
determined by various parameters, including injec-
n the mold, resin temperature, viscosity, and preform
permeability depends on fiber material type, fiber
e fraction, through-ply vs. in-plane flow, and several
old filling, the resin follows the path of least resis-
difficulty when impregnating tightly packed
yarns
dels have been developed to numerically simulate
through preforms. These models are used during
to predict the optimal locations for inlet ports and
tion sequencing, thus achieving the goals of minimal
e and elimination of incomplete mold filling or dry
ically rely on a two-dimensional version of Darcy’s
nalysis to describe resin flow through the preforms.
ensional nature of these models, they are limited to
uniform thickness.
er wet-out) are the biggest challenge for the RTM
composite structure lead to part rejection and there-
to production yield. To aid good resin flow and to
m at the vents is sometimes applied to displace air
nts. Vacuum also helps in rapid mold filling. Mold
ly before the onset of cross-linking. Once the mold
resin, it is allowed to cure rapidly for faster demold-
lyesters and vinylesters, cross-linking starts at room
other resins require heat for rapid curing. During
d and a certain back-pressure is maintained at inlet
ls. Once the resin is cured, the mold is opened and
pplying Heat and Pressure
e RTM process is applied in the mold using resin
injection pressure helps the resin to flow inside the
edia and allows the resin to fill the cavity. The RTM
essor that injects resin at a certain pressure. Typically,
low and in the range of 10 to 100 psi (69 to 690 kPa).
determines the flow rate of the resin, and thus the
r the mold is completely filled with the resin, the
uring curing is kept at around 2 to 10 psi. Resin
ds on the resin viscosity, mold size, permeability of
time needed, and cure kinetics of the resin. The resin
ssing is kept low, typically between 100 and 500 cP
© 2002 by CRC Press LLC
(centipoise) so that it d
dispensing equipment.
Temperature selection
resin. The resin supplier
ing the preheat tempera
6.8.6.6 Basic Process
For simplicity in under
for the fabrication of a
through 6.58. Figure 6.5
ing under controlled-te
mold as shown in Figu
into mold under exactin
onstrating standard des
system, and self-clamp
processing is complete
Figure 6.59, and then ma
amount of machining a
Figure 6.60 represents a
mated tooling for the p
is used to make high-vo
molding technique. Usi
than 35,000 engine vane
by adding more tools o
The steps during the
1. A thermoset resi
dispensing equip
2. A release agent is
Sometimes, a gel
FIGURE 6.55
Preform fabrication using vac
tesy of Intellitec.)
oes not go beyond the pumping capabilities of the
during RTM processing depends on the type of
recommends specific processing conditions, includ-
ture, mold temperature, and curing temperature.
ing Steps
standing the complete RTM process, the basic steps
composite component are shown in Figures 6.55
5 shows preform fabrication using vacuum debulk-
mperature parameters. The preform is loaded into a
re 6.56. Figure 6.57 illustrates injection of the resin
g processing parameters. A typical RTM mold dem-
ign features, such as oil connections, injection runner
ing/loading devices, is shown in Figure 6.58. After
, the part is removed from the mold, as shown in
chining and finishing operations are performed. The
nd finishing depends on the complexity of the part.
manufacturing cell showing multicavity semi-auto-
roduction of engine vanes. This manufacturing cell
lume RTM parts and utilizes the “drop and shoot”
ng this technique, Intellitec annually produces more
s for AlliedSignal, and this number can be increased
r by adding more shifts.
RTM process are summarized below:
n and catalyst are placed in tanks A and B of the
ment.
uum debulking under controlled-temperature parameters. (Cour-
applied to the mold for easy removal of the part.
coat is applied for good surface finish.
© 2002 by CRC Press LLC
3. The preform is p
4. The mold is heat
5. Mixed resin is in
and pressure. So
assist in resin flo
6. Resin is injected
is turned off and
mold is increased
7. After curing for
chemistry), the c
FIGURE 6.56
Preform loading into a mold
FIGURE 6.57
Resin injection into a mold b
laced inside the mold and the mold is clamped.
ed to a specified temperature.
jected through inlet ports at selected temperature
metimes, a vacuum is created inside the mold to
w as well as to remove air bubbles.
until the mold is completely filled. The vacuum
the outlet port is closed. The pressure inside the
to ensure that the remaining porosity is collapsed.
using innovative mold rotating fixture. (Courtesy of Intellitec.)
y a technician. (Courtesy of Intellitec.)
a certain time (6 to 20 min, depending on resin
omposite part is removed from the mold.
© 2002 by CRC Press LLC
FIGURE 6.58
A typical RTM mold demons
runner system, and self-clam
FIGURE 6.59
Demolding component in a d
trating standard design features such as oil connections, injection
ping/loading devices. (Courtesy of Intellitec.)
edicated tool breakout cell. (Courtesy of Intellitec.)
© 2002 by CRC Press LLC
6.8.6.7 Advantages o
Recently, RTM has gain
its potential to make sm
ner. RTM provides oppo
of structural component
its major advantages ove
1. Initial investmen
operating expen
injection moldin
market evaluatio
using an RTM pr
investment was
2. Moldings can be
3. RTM processing
rates. This featur
manner. This len
there is a growin
model and quick
FIGURE 6.60
Manufacturing cell depicting
vanes. (Courtesy of Intellitec.
f the Resin Transfer Molding Process
ed importance in the composites industry because of
all to large complex structures in a cost-effective man-
rtunities to use continuous fibers for the manufacture
s in low- to medium-volume environments. Some of
r other composites manufacturing techniques include:
t cost is low because of reduced tooling costs and
ses as compared to compression molding and
g. For this reason, prototypes are easily made for
n. For example, the dish antenna was first made
ocess to validate the design features before capital
made for compression molding of SMC parts.
manufactured close to dimensional tolerances.
can make complex parts at intermediate volume
e allows limited production runs in a cost-effective
ds benefits to the automotive market, in which
g need toward lower production volumes per car
er changes to appeal to more niche markets.
multicavity semi-automated tooling for the manufacture of engine
)
© 2002 by CRC Press LLC
4. RTM provides fo
finish on both si
finishes.
5. RTM allows for p
forcement and ac
6. Higher fiber volu
7. Inserts can be ea
good joining and
8. A wide variety o
9. RTM offers low v
closed molding p
10. RTM offers prod
wastage and red
11. The process can b
with less scrap.
6.8.6.8 Limitations o
Although RTM has ma
cesses, it also has the fo
1. The manufacture
and-error experi
sure that porosit
2. Tooling and equi
for hand lay-up
3. The tooling desig
A comparison of RTM
TABLE 6.3
Comparison of RTM w
Molding Process
RTM
Open molding (hand
lay-up, spray-up)
SRIM
Compression molding
(SMC, BMC)
Injection molding
2
1
M
M
M
r the manufacture of parts that have a good surface
des. Sides can have similar or dissimilar surface
roduction of structural parts with selective rein-
curate fiber management.
me fractions, up to 65%, can be achieved.
sily incorporated into moldings and thus allows
assembly features.
f reinforcement materials can be used.
olatile emission during processing because of the
rocess.
uction of near-net-shape parts, hence low material
uced machining cost.
e automated, resulting in higher production rates
f the Resin Transfer Molding Process
ny advantages compared to other fabrication pro-
llowing limitations.
of complex parts requires a good amount of trial-
mentation or flow simulation modeling to make
y- and dry fiber-free parts are manufactured.
pment costs for the RTM process are higher than
and spray-up processes.
n is complex.
with other molding process is presented in Table 6.3.
ith Other Molding Processes
Production
Rate/Year
Cycle
Time
(min)
Emission
Concerns
Two-Sided
Part
Possible?
00–10,000
00–500
ore than 10,000
ore than 10,000
6–30
60–180
3–20
1–20
No
Yes
No
No
Yes
No
Yes
Yes
ore than 20,000 0.5–2 No (very safe) Yes
© 2002 by CRC Press LLC
6.8.6.9 Variations of
There are several varia
mercial sector. Some of
6.8.6.9.1 VARTM
VARTM is an adaptatio
making large structures
cut in half because one-
part. In this infusion p
cover, either rigid or fle
seal. A vacuum procedu
various types of ports. T
wet lay-up process used
closed mold process, st
fiber volume fraction (7
structural performance
6.8.6.9.2 SCRIMP
SCRIMP stands for See
patented technology of
panies. SCRIMP works
process is similar to the
of 27 to 29 in. Hg is draw
into the layers. In this w
core are infused with r
placement. In addition,
consisting of a special re
devices as shown in Fig
the marine industry.
Applications for the S
seaports, windmill blad
car bodies, amusement
components. The bigge
the wet lay-up process
emissions. Moreover, dr
time during processing
6.8.7 Structural Reac
The SRIM process is sim
in the resin used and t
SRIM process, two resin
high velocity just before
at a speed of 100 to 200 m
the RTM Process
tions of the RTM process that are used in the com-
them are described below.
n of the RTM process and is very cost-effective in
such as boat hulls. In this process, tooling costs are
sided tools such as open molds are used to make the
rocess, fibers are placed in a one-sided mold and a
xible, is placed over the top to form a vacuum-tight
re is used to draw the resin into the structure through
his process has several advantages compared to the
in manufacturing boat hulls. Because VARTM is a
yrene emissions are close to zero. Moreover, a high
0%) is achieved by this process and therefore high
is obtained in the part.
mann Composite Resin Infusion Molding Process, a
the Seemann, TPI, and HardCore Composites com-
especially well for medium- to large-sized parts. The
VARTM process. In this process, a steady vacuum
n to first compact the layers and then to draw resin
ay, fiber compaction occurs before the filaments and
esin, thus eliminating voids and ensuring accurate
SCRIMP uses a patented resin distribution system
sin flow medium combined with simple mechanical
ure 6.61. The major use of the SCRIMP process is in
CRIMP process include marine docking fenders for
es, satellite dishes, railroad cars, buses, customized
park rides, physical therapy pools, and aerospace
st advantages of the SCRIMP process compared to
lie in its weight control and absence of styrene
y lay-up of fabric and core materials saves labor and
.
tion Injection Molding (SRIM) Process
ilar to the RTM process, with the difference being
he method of mixing resins before injection. In the
s A and B are mixed in a mixing chamber at a very
injecting into the mold (Figure 6.62). The resin flows
/s and collides in the mixing chamber. The pressure
© 2002 by CRC Press LLC
FIGURE 6.61
Schematic of the SCRIMP pro
FIGURE 6.62
Schematic of the SRIM proce
Vacuum bag
Mold
Reinforcements
Core
Reinforcements
SCRIMP medium
Mold h
cess.
VacuumResin
Liquid A Liquid B
Cleaning piston
Mixing chamber Liquid jets
Preformalves
ss.
© 2002 by CRC Press LLC
generated during collisi
is injected into the mol
used to prevent the wa
for the SRIM process is
polyisocyanurate (base
injected into the mold, w
the SRIM process can b
The SRIM process wa
ing) process, in which
chamber and then the r
preform. The compone
absence of fibers. The R
nents because it provid
SRIM processes, cross-li
of two resins; therefore,
(cross-linking) process.
begins to gel in few seco
to a certain temperature
complete cross-linking,
This requirement (the co
increase the cost of RIM
To add strength to R
molding) process was d
added to one of the resi
The fiber lengths are k
resin viscosity low. RRI
RIM parts; however, fro
The RRIM process is us
and fascia. To utilize th
SRIM was developed. S
and is used for making
6.8.7.1 Major Applic
The SRIM process is u
where high-volume pro
made in a process cycle
the Automotive Comp
Chrysler, Ford, and Ge
pickup truck boxes. Ot
body panels.
6.8.7.2 Basic Raw M
The reinforcements for t
Glass is the most comm
on is in the range of 10 to 40 MPa although the resin
d at a pressure of less than 1 MPa. Low pressure is
sh-out of fibers at the injection port. The resin used
of very low viscosity and the most common resin is
d on polyurethane chemistry). This mixed resin is
hich contains fiber preforms. The preform used for
e made of short or long fibers.
s developed from the RIM (reaction injection mold-
two resins are mixed at high velocity in a mixing
esin is injected into a closed mold where there is no
nts made by the RIM process is weak because of
IM process is used for making automotive compo-
es a high-volume production capacity. In RIM and
nking of the polymers is initiated by the rapid mixing
this process does not require heat to start the curing
The cross-linking process is very rapid and the resin
nds after injection into the mold. The mold is heated
to aid the rapid cross-linking of the resin. To ensure
the two resins must be mixed in the correct ratio.
rrect amount of mixing) as well as fast impingement
equipment.
IM parts, the RRIM (reinforced reaction injection
eveloped. In RRIM, short or milled glass fibers are
n components before being mixed into the chamber.
ept less than 0.02 in. (0.5 mm) in order to keep the
M parts are stiffer and more damage tolerant than
m a structural point of view, RRIM parts are weaker.
ed in automotive applications to make body panels
e short processing cycle time of the RIM process,
RIM is basically the combination of RIM and RTM,
structural parts of reasonable strength.
ations
sed in applications (e.g., the automotive industry)
duction at low cost is required. SRIM parts can be
time of 1 to 5 min, depending on part size. Recently,
osites Consortium (general partnership of Daimler
neral Motors) utilized the SRIM process to make
her applications include bumper beams, fascia, and
aterials
his process are preforms made of short or long fibers.
on fiber type used in this process. With the drop in
© 2002 by CRC Press LLC
carbon fiber price, carbo
The main resin materi
(polyisocyanurate resin
low (10 to 100 cP) compa
rate for the resins used i
and vinylester resins th
6.8.7.3 Tooling
SRIM utilizes a closed
SRIM process are heavi
the tools are made of st
tooling requirements.
6.8.7.4 Making of th
The procedure to make
main difference being
resin mixing procedure
chemically more reactiv
typically made of short
of continuous fibers (br
Figure 2.18 in Chapte
or multiple guns direct
a preform screen. Vacuu
plastic binder is minim
the preform is prepared
is clamped and resin is
SRIM process is less th
cesses and greater than
away. Because the chem
completely fill the mol
usually 1 to 5 min, dep
the part has solidified, t
the mold.
6.8.7.5 Methods of A
The resins used in the S
the mold cavity needs
resin injection is very hi
rate, care should be take
front. Fiber wash-out ca
tion and low resin visc
pensing equipment. The
range as for the RTM p
n fiber is also being considered for the SRIM process.
als for this process are polyurethane-based resins
). The resin viscosity for the SRIM process is quite
red to the RTM process (100 to 1000 cP). The reaction
n the SRIM process is much faster than the polyester
at are mostly used in the RTM process.
mold similar to the RTM process but tools for the
er and more expensive than RTM tools. In general,
eel. Refer to Section 6.8.6.3 for more information on
e Part
SRIM parts is very similar to the RTM process, the
that in SRIM, the resin dispensing equipment and
are different. Moreover, the resin used in SRIM is
e than in RTM. In the SRIM process, the preform is
fibers; whereas in RTM, the preform is usually made
aided preforms) or short fibers.
r 2 depicts a schematic for making preforms. Single
the glass fibers and thermoplastic-fiber binder onto
m keeps the fibers in place. The amount of thermo-
al, just enough to hold the preform together. Once
, it is placed in the mold for resin injection. The mold
rapidly injected. The clamping force needed for the
an that for compression and injection molding pro-
the RTM process. Care is taken to avoid fiber wash-
ical reactivity of the resin is very high, the resin must
d before it starts gelling. The process cycle time is
ending on the size and geometry of the part. Once
he mold is unclamped and the part is removed from
pplying Heat and Pressure
RIM process have a high reaction rate and therefore
to be filled rapidly. This also means that the rate of
gh in the SRIM process. Because of the high injection
n to avoid the fiber wash-out due to advancing resin
n be minimized by having a low fiber volume frac-
osity. The resin is injected into the mold using dis-
inlet pressure for the SRIM process falls in the same
rocess. For curing of the resin, no heat is required.
© 2002 by CRC Press LLC
6.8.7.6 Basic Process
The major manufacturi
marized as follows:
1. The preform is p
2. The release agen
on the mold.
3. The mold is clam
4. The resin inlet h
5. The mold is preh
6. Resin mixing is i
7. Resin is injected
8. After mold fillin
9. The composite p
6.8.7.7 Advantages o
SRIM is becoming the p
production is required.
1. It is very suitabl
cost, in particula
2. Small- to large-s
made with this t
6.8.7.8 Limitations o
SRIM is highly suitable
the following limitation
1. It requires a larg
2. The tooling cost
3. A high fiber vol
the maximum fib
6.8.8 Compression M
Compression molding
of its high volume capa
motive panels. Sheet m
pounds (BMCs) are th
molding. Compression
using prepregs and cor
pression molding of SM
ing Steps
ng steps used during the SRIM process can be sum-
repared on-site or bought from a supplier.
t is applied to the mold and the preform is placed
ped.
ose is connected to the inlet ports of the mold.
eated according to requirements.
nitiated by operating the dispensing equipment.
into the mold.
g and curing of the resin, the mold is declamped.
art is removed from the mold.
f the SRIM Process
rocess of choice for applications where high-volume
SRIM provides the following advantages.
e for making high-volume structural parts at low
r for making automotive parts.
ized parts with complex configurations can be
echnique.
f the SRIM Process
for high-volume applications. However, SRIM has
s.
e capital investment in equipment.
for the SRIM process is high.
ume fraction cannot be attained by this process;
er volume fraction achievable is about 40%.
olding Process
is very popular in the automotive industry because
bilities. This process is used for molding large auto-
olding compounds (SMCs) and bulk molding com-
e more common raw materials for compression
molding is also used for making structural panels
e materials; but because of the popularity of com-
C, the molding of SMC is discussed here.
© 2002 by CRC Press LLC
Compression molding
ilarity to the stamping p
ing process for a long t
Similarly today, compr
for the auto industry. In
is produced in one mol
ation, the steel sheet m
get the final shape. Ther
tages over the stamping
and equipment. One of
to include ribs and bos
and nonuniform thickne
avoiding secondary ope
Compression moldin
surfaces, the overall per
smoothness of the surfa
there is a trade-off in g
surface quality. Short ri
piece components are u
Class A panels should b
sink marks. However,
side can be eliminated
6.8.8.1 Major Applic
Compression molding o
for automotive applicat
fixed and can be suppor
quarter panels, fenders
ages, and limited-acces
panels are used for clos
panels are usually supp
should have enough rig
is obtained by joining i
FIGURE 6.63
Compression molded two-pie
Ad
is popular in the auto industry because of its sim-
rocess. The auto industry has been using the stamp-
ime and has built good know-how for this process.
ession molding has become quite a mature process
compression molding of SMC, the final component
ding operation steel whereas in the stamping oper-
etal goes through a series of stamping processes to
efore, compression molding provides several advan-
process and saves significant cost in terms of molds
the advantages of SMC over steel lies in its ability
ses in a third dimension. Holes, flanges, shoulders,
sses can be created during the molding process, thus
rations such as welding, drilling, and machining.
g is used for making Class A surfaces. For Class A
centage of fiber content is limited to 30% to optimize
ce as well as to reduce fiber read-through. Therefore,
etting mechanical property enhancement or Class A
bs are used on body panels and other one- and two-
sed to increase the stiffness of these panels. Ribs on
e used cautiously because of their potential to cause
with proper design, sink marks formed on the top
or minimized.
ations
f SMC is used for making one- and two-piece panels
ions. One-piece panels are used where the panel is
ted around the majority of its periphery. Roof panels,
, and add-ons such as spoilers, ground-effects pack-
s panels are examples of this category. Two-piece
ure panels such as doors, hoods, and decklids. These
orted by hinges with body structures and therefore
idity of their own. The stiffness of two-piece panels
nner and outer panels as shown in Figure 6.63.
hesive
ce panel. Two-piece panels rely on closed sections for stiffness.
© 2002 by CRC Press LLC
Other applications of
military drop-boxes, pic
sleeper cabs, engine co
water crafts (PWCs), an
applications of compre
door lamps, lamp hous
6.8.8.2 Basic Raw M
SMC, BMC, and TMC
molding operations. Th
Chapter 2. The SMC is
into a sheet product th
(47.25 in.) wide. SMC is
square pieces. SMC has
manufactured within 2 w
material is stored at B-s
These molding comp
cost $0.70 to $1.50/lb. Th
polyester resins and calc
6.8.8.3 Making of th
In compression molding
placed on the bottom h
These rectangular plies a
of the total area, and the
The amount of charge is
of the part. The mold is
certain velocity. Typical
SMC and 80 mm/s with
moplastic resins such as
is discussed in the therm
In compression moldi
With the movement of
fills the cavity. The flo
entrapped air from the
amount of cure under h
removed from the mold
of the part. Typical mold
and 1 to 2 min for a tw
time of 1 to 2 min. Figure
an automotive part. An S
The parts made by co
RTM, injection molding
tions, the temperature
the compression molding process include skid plates,
kup box components, radiator supports, heavy-truck
mponents such as rocker covers/oil pans, personal
d home applications such as showers/tubs. Electrical
ssion molding processes are enclosures, fuses, out-
ings, switches, street light canopying, and more.
aterials
are used as initial raw materials for compression
ese molding compounds are described in detail in
obtained by mixing liquid resin, fillers, and fibers
at is usually about 4 mm (0.16 in.) thick and 1.2 m
stored in rolled form or in a stack of rectangular or
a limited shelf life and the part should be usually
eeks of manufacturing the molding compound. The
tage.
ounds
are fairly inexpensive material and typically
e main ingredients in these materials are glass fibers,
ium carbonate; up to 50% fillers can be used in SMC.
e Part
operation, the SMC is cut into rectangular sizes and
alf of the preheated mold as shown in Figure 6.64.
re called charge. The charge usually covers 30 to 90%
remaining area is filled by forced flow of the charge.
determined by calculating the final volume or weight
closed by bringing the upper half of the mold to a
ly, the working speed of the mold is 40 mm/s with
GMT. GMT is made using glass fiber mat and ther-
polypropylene (PP). Compression molding of GMT
oplastic manufacturing processes section (Section 6.9).
ng, the molds are usually preheated to about 140°C.
mold, the charge starts flowing inside the mold and
w of the molding compound causes removal of
mold as well as from the charge. After a reasonable
eat and pressure, the mold is opened and the part is
. Ejector pins are often used to facilitate easy removal
cycle times are about 1 to 4 min for a one-piece panel,
o-piece panel. Two-piece panels require an assembly
6.65 shows a molding press with ejector pins ejecting
MC molded automotive part is shown in Figure 6.66.
mpression molding are usually thin as compared to
, and other manufacturing processes. For thin sec-
across the thickness remains uniform and is in the
© 2002 by CRC Press LLC
neighborhood of the m
thickness allows unifor
in the part caused by c
tribution is not uniform
adjacent to the mold r
uniform. It takes some
perature because of th
However, because of th
temperature of the cen
curing completes, the c
Compression moldin
defects could be on the
or fiber read-throughs)
lines, and warpage). Po
ters are interlaminar cr
gas pressure inside the
from unreacted styrene
FIGURE 6.64
Schematic of the compression
Charge
Ejector pin
old temperature. Uniform temperature across the
m curing in the part and thus avoids residual stress
uring. For thick cross sections, the temperature dis-
across the thickness. In thick sections, the layer
eaches the mold temperature quickly and remains
time for the centerline layer to reach the mold tem-
e low thermal conductivity of the charge material.
e exothermic curing reaction of resin material, the
terline layer goes above the mold temperature. As
enterline temperature flattens to mold temperature.
g of SMC has the potential for several defects. The
outer surface (such as an unacceptable surface finish
or internal defects (such as porosities, blisters, weld
rosities are caused by air entrapment, whereas blis-
acks formed at the end of molding due to excessive
molding process.
Applied pressure
Male mold half
Guidance pin
Female mold half
molded part. This internal gas pressure may result
monomer in undercured parts or from large pockets
© 2002 by CRC Press LLC
of entrapped air betwe
two flow fronts meet i
properties normal to the
along the weld line. Wa
Typically, parts with n
rate between sections o
a potential source of res
SMC panels usually r
modulus of SMC R25 is
is 30 Msi. In one-for-on
larger than the compar
many cases, closed sect
require section enlarge
loads are applied in on
equal stiffness is achiev
modulus fibers. Figure
FIGURE 6.65
Compression molding press.
en the stacked layers. Weld lines are formed when
nside the mold. Weld lines have poor mechanical
weld line because the fibers tend to align themselves
rpage in the composite results from residual stress.
onuniform cross-section have variations in cooling
f different thickness. This differential cooling rate is
idual stress and thus warpage in the component.
eplace steel panels in the auto industry. The tensile
1.2 to 1.8 Msi, SMC R50 is 1.8 to 2.8 Msi, and steel
e replacement, the SMC cross section needs to be
able steel section to provide the same stiffness. In
ions, as shown in Figure 6.67 for two-piece panels,
ment only in one direction (thickness direction) if
e plane. If section enlargement is not possible, then
(Courtesy of Ranger Group, Italy.)
ed through the use of ribs, doublers, or added higher
6.67 shows the rib geometry for Class A surface and
© 2002 by CRC Press LLC
nonappearance surface.
be 75% of the nominal p
for ribs is 0.06 in. A mi
for part removal from
for ribs are relaxed, as
structural performance.
Dimensional control a
requirements for the au
pression molded parts
FIGURE 6.66
SMC molded automotive com
FIGURE 6.67
Rib geometry for various typ
T
0.0
0
(a)
The base of ribs opposite the Class A surface should
anel thickness.24 The minimum allowable thickness
nimum of 0.5° of draft per side is required to allow
the mold. In low visibility areas, the design criteria
shown in Figure 6.67b, to enhance moldability and
nd part repeatability of a process are very important
ponent. (Courtesy of Ranger Group, Italy.)
es of surfaces: (a) Class A surface and (b) nonappearance surface.
2-in. maximum radius
.5° draft
T
1.0° draft
0.06-in. radius
(b)
tomotive industry. Some sources of variation in com-
that affect process repeatability include:
© 2002 by CRC Press LLC
1. Press parallelism.
on press parallel
equipment sup
Advance-control
are expensive. F
compensated by
2. Mold tolerances. E
part tolerances. T
surface of the m
surface areas.
3. Molded datum fea
of a part are estab
feature of a part t
datum features
blies. The molde
datums on the se
of tolerances.
4. Material shrinkag
dimension cause
contraction of th
shrink when coo
mold material w
temperature, the
part shrinks less
Some formulatio
0.15%. Curing sh
polymer molecul
proceeds. The vo
resins is in the ra
The addition of fi
A typical non-Cla
of more than 0.0
Molds for compressio
material formulations to
to verify part fit if mater
It is very important t
molding operation. The
surface in molded parts
1. Avoid flatness. On
panel look disto
mended to elimin
2. Maintain uniform
uniform thicknes
The thickness variation in a molded part depends
ism tolerances as well as mold tolerances. Each
plier has its own tolerances on parallelism.
presses provide low tolerance variation, but they
or two-piece panels, thickness variation can be
varying bond line thickness.
very mold and tool has tolerances that can affect
he use of computer math data in cutting the part
old increases the accuracy of the mold over large
tures. In dimensioning, geometric characteristics
lished from a datum. A datum feature is an actual
hat is used to establish a datum. The use of molded
will increase the repeatability in bonded assem-
d datums reduce the need to locate and maintain
condary fixtures and thus reduce additional sets
e. Shrinkage is the reduction in volume or linear
d by curing of the resin as well as by thermal
e material. Materials expand when heated and
led. If the molded panel contracts more than the
hen it is cooled from mold temperature to room
n it is called shrinkage in the part. If the molded
than the mold material, it is called expansion.
ns can exhibit an apparent expansion of up to
rinkage occurs because of the rearrangement of
es into a more compact mass as the curing reaction
lumetric shrinkage of cast polyester and vinylester
nge of 5 to 12%, whereas for epoxy, it is 1 to 5%.
bers and fillers reduces the amount of shrinkage.
ss A formulation will have an apparent shrinkage
5%.
n molding are built by keeping in mind the type of
be used in making parts. Therefore, it is important
ial formulation is changed after the mold is machined.
o know how to create a Class A surface during the
following are some guidelines for making a Class A
16:
flat panels, reflected highlights often make the
rted and therefore a contoured surface is recom-
ate objectionable highlights on high-gloss surfaces.