Plastics Engineering

530 Pages·1998·21.982 MB·English

by  R .J. Crawford

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PLASTICS
ENGINEERING

PLASTICS
ENGINEERING
Third Edition
R.J. Crawford, BSc, PhD, DSc, FEng, FIMechE, FIM
Department of Mechanical, Aeronautical
and Manufacturing Engineering
The Queen’s University of Belfast
l
E I N E M A N N
OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS
SAN DlEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO
Butterworth-Heinemann
An imprint of Elsevier Science
Linacre House. Jordan Hill, Oxford OX2 8DP
225 Wildwood Avenue, Woburn, MA 01801-2041
First published 1981
Second edition 1987
Reprinted with corrections 1990. 1992
Third edition 1998
Reprinted 1999.2001, 2002
Copyright 0 1987, 1998 R.J. Crawford. All rights reserved
The right of R.J. Crawford to be identified as
the author of this work has been asserted in
accordance with the Copyright. Designs and
Patents Act 1988
No part of this publication may be reproduced in
any material form (including photocopying or
storing in any medium by electronic means and
whether or not transiently or incidentally to some
other use of this publication) without the written
permission of the copyright holder except in
accordance with the provisions of the Copyright,
Designs and Patents Act 1988 or under the terms of a
licence issued by the Copyright Licensing Agency Ltd,
90 Tottenham Court Road, London, England WIT 4LP.
Applications for the copyright holder’s written permission
to reproduce any part of this publication should be addressed
to the publishers.
British Library Cataloguing in Publication Data
Crawford, R.J. (Roy J.)
Plastics engineering. 3rd ed.
1. Plastics
I. Title
668.4
ISBN 0 7506 3764 1
Library of Congress Cataloguing in Publication Data
Crawford, R.J.
Plastics engineering/R.J. Crawford - 3rd ed.
p. cm.
Includes index.
ISBN 0 7506 3764 1 (pbk).
1 Plastics. I Title
TP1120 C74 97-36604
668.4 - dc21 CIP
For information on all Butterworth-Heinemann publications
visit our website at www.bh.com
Typeset by Laser Words, Chennai, India
Printed by St Edmundsbury Press Ltd, Bury St Edmunds, Suffolk
Contents
Preface to the Third Edition xi
...
Preface to the Second Edition Xlll
Preface to the First Edition xv
Chapter 1 - General Properties of Plastics 1
1.1 Introduction 1
1.2 Polymeric Materials 2
1.3 Plastics Available to the Designer 6
1.3.1 Engineering Plastics 6
1.3.2 Thermosets 7
1.3.3 Composites 8
1.3.4 Structural Foam 9
1.3.5 Elastomers 9
1.3.6 Polymer Alloys 11
1.3.7 Liquid Crystal Polymers 12
1.4 Selection of Plastics 18
1.4.1 Mechanical Properties 18
1.4.2 Degradation 26
1.4.3 Wear Resistance and Frictional Properties 28
1.4.4 Special Properties 30
1.4.5 Processing 35
1.4.6 Costs 37
vi Contents
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Chapter 2 Mechanical Behaviour of Plastics 41
2.1 Introduction 41
2.2 Viscoelastic Behaviour of Plastics 42
2.3 Short-Term Testing of Plastics 43
2.4 Long-Term Testing of Plastics 45
2.5 Design Methods for Plastics using Deformation Data 48
2.6 Thermal Stresses and Strains 61
2.7 Multi-layer Mouldings 66
2.8 Design of Snap Fits 71
2.9 Design of Ribbed Sections 74
2.10 Stiffening Mechanisms in Other Moulding Situations 81
2.1 1 Mathematical Models of Viscoelastic Behaviour 84
2.12 Intermittent Loading 95
2.12.1 Superposition Principle 95
2.12.2 Empirical Approach 103
2.13 Dynamic Loading of Plastics 110
2.14 Time-Temperature Superposition 116
2.15 Fracture Behaviour of Unreinforced Plastics 119
2.16 The Concept of Stress Concentration 121
2.17 Energy Approach to Fracture 121
2.18 Stress Intensity Factor Approach to Fracture 127
2.19 General Fracture Behaviour of Plastics 131
2.20 Creep Failure of Plastics 134
2.20.1 Fracture Mechanics Approach to Creep Fracture 136
2.20.2 Crazing in Plastics 137
2.21 Fatigue of Plastics 138
2.21.1 Effect of Cyclic Frequency 140
2.21.2 Effect of Waveform 142
2.21.3 Effect of Testing Control Mode 142
2.2 1.4 Effect of Mean Stress 143
2.21.5 Effect of Stress System 145
2.21.6 Fracture Mechanics Approach to Fatigue 145
2.22 Impact Behaviour of Plastics 147
2.22.1 Effect of Stress Concentrations 148
2.22.2 Effect of Temperature 150
2.22.3 Miscellaneous Factors Affecting Impact 152
2.22.4 Impact Test Methods 152
2.22.5 Fracture Mechanics Approach to Impact 154
Chapter 3 - Mechanical Behaviour of Composites 168
3.1 Deformation Behaviour of Reinforced Plastics 168
3.2 Types of Reinforcement 168
Contents vii
3.3 Types of Matrix 170
3.4 Forms of Fibre Reinforcement in Composites 171
3.5 Analysis of Continuous Fibre Composites 172
3.6 Deformation Behaviour of a Single Ply or Lamina 182
3.7 Summary of Approach to Analysis of Unidirectional
Composites 188
3.8 General Deformation Behaviour of a Single Ply 195
3.9 Deformation Behaviour of Laminates 202
3.10 Summary of Steps to Predict Stiffness of Symmetric
Laminates 206
3.11 General Deformation Behaviour of Laminates 208
3.12 Analysis of Multi-layer Isotropic Materials 218
3.13 Analysis of Non-symmetric Laminates 223
3.14 Analysis of Short Fibre Composites 226
3.15 Creep Behaviour of Fibre Reinforced Plastics 232
3.16 Strength of Fibre Composites 232
3.16.1 Strength of Single Plies 234
3.16.2 Strength of Laminates 236
3.17 Fatigue Behaviour of Reinforced Plastics 238
3.18 Impact Behaviour of Reinforced Plastics 240
Chapter 4 - Processing of Plastics 245
4.1 Introduction 245
4.2 Extrusion 246
4.2.1 General Features of Single Screw Extrusion 246
4.2.2 Mechanism of Flow 25 1
4.2.3 Analysis of Flow in Extruder 252
4.2.4 ExtruderDie Characteristics 257
4.2.5 Other Die Geometries 259
4.2.6 General Features of Twin Screw Extruders 262
4.2.7 Processing Methods Based on the Extruder 264
4.3 Injection Moulding 278
4.3.1 Introduction 278
4.3.2 Details of the Process 279
4.3.3 Moulds 285
4.3.4 Structural Foam Injection Moulding 297
4.3.5 Sandwich Moulding 298
4.3.6 Gas Injection Moulding 299
4.3.7 Shear Controlled Orientation in Injection Moulding
(SCORIM) 30 1
4.3.8 Reaction Injection Moulding 302
...
Vlll Contents
4.3.9 Injection Blow Moulding 303
4.3.10 Injection Moulding of Thermosetting Materials 304
4.4 Thermoforming 306
4.4.1 Analysis of Thermoforming 309
4.5 Calendering 313
4.5.1 Analysis of Calendering 315
4.6 Rotational Moulding 318
4.6.1 Slush Moulding 323
4.7 Compression Moulding 323
4.8 Transfer Moulding 326
4.9 Processing Reinforced Thermoplastics 327
4.10 Processing Reinforced Thermosets 328
4.10.1 Manual Processing Methods 330
4.10.2 Semi-Automatic Processing Methods 332
4.10.3 Automatic Processes 337
Chapter 5 - Analysis of polymer melt flow 343
5.1 Introduction 343
5.2 General Behaviour of Polymer Melts 344
5.3 Isothermal Flow in Channels: Newtonian Fluids 346
5.4 Rheological Models for Polymer Melt Flow 35 1
5.5 Isothermal Flow in Channels: Non-Newtonian Fluids 354
5.6 Isothermal Flow in Non-Uniform Channels 357
5.7 Elastic Behaviour of Polymer Melts 363
5.8 Residence and Relaxation Times 367
5.9 Temperature Rise in Die 368
5.10 Experimental Methods Used to Obtain Flow Data 369
5.11 Analysis of Flow in Some Processing Operations 375
5.12 Analysis of Heat 'lkansfer during Polymer Processing 39 1
5.13 Calculation of Clamping force 40 1
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Appendix A Structure of Plastics 413
A.l Structure of Long Molecules 413
A.2 Conformation of the Molecular Chain 415
A.3 Arrangement of Molecular Chains 420
Appendix B - Solution of Differential Equations 425
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Appendix C Stredstrain Relationships 426
Appendix D - Stresses in Cylindrical Shapes 429
Contents ix
Appendix E - Introduction to Matrix Algebra 43 1
E.1 Matrix definitions 43 1
E.2 Matrix multiplication 432
E.3 Matrix addition and subtraction 432
E.4 Inversion of a matrix 433
E.5 Symmetric matrix 433
Appendix F - Abbreviations for some Common Polymers 434
Solutions to Questions 435
Index 50 1