Structural Adhesive Joints in Engineering

316 Pages·1984·8.78 MB·English

by  Robert D. Adams BSc (Eng.) (Lond.)

Structural Adhesive Joints in Engineering
Structural Adhesive Joints
in Engineering
ROBERT D. ADAMS
BSc (Eng.) (Lond.), PhD(Cantab.), ACGI, C Eng., FIMechE, FInstP
Reader in Mechanical Engineering, University of Bristol, UK
and
WILLIAM C. WAKE
MSc, PhD, DSc(Lond.), FRSC, FPRI, Hon.DSc (The City University)
Hon. Fellow, The City University, London, UK
ELSEVIER APPLIED SCIENCE PUBLISHERS
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ELSEVIER SCIENCE PUBLISHING CO., INe.
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British Ubrary Cataloguing in Publication Data
Adams, R. D.
Structural adhesive joints in engineering.
1. Adhesive joints
1. Title II. Wake, William C.
624.1'89'9 TA492.A3
ISBN-13 :978-94-0 10 -8977-7 e-ISBN-13 :978-94-009-5616-2
DOI: 10.1007/978-94-009-5616-2
WITH 30 TABLES AND 125 ILLUSTRATIONS
© ELSEVIER APPLIED SCIENCE PUBLISHERS LID 1984
Reprinted 1986
Softcover reprint ofthe hardcover 1st edition 1984
Special regulations for readers in the USA
This publication has been registered with the Copyright Clearance Center
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copying outside of the USA, should be referred to the publisher.
All rights reserved. No part of this publieation may be reprodueed, stored
in a retrieval system, or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording, or otherwise, without the
prior written permission of the publisher.
Preface
The intention of this book is that it should contain everything an
engineer needs to know to be able to design and produce adhesively
bonded joints which are required to carry significant loads. The advan
tages and disadvantages of bonding are given, together with a sufficient
understanding of the necessary mechanics and chemistry to enable the
designer to make a sound engineering judgement in any particular
case.
The stresses in joints are discussed extensively so that the engineer
can get sufficient philosophy or feel for them, or can delve more deeply
into the mathematics to obtain quantitative solutions even with elasto
plastic behaviour. A critical description is given of standard methods of
testing adhesives, both destructively and non-destructively. The essen
tial chemistry of adhesives and the importance of surface preparation
are described and guidance is given for adhesive selection by me ans of
check lists. For many applications, there will not be a unique adhesive
which alone is suitable, and factors such as cost, convenience, produc
tion considerations or familiarity may be decisive. A list of applications
is given as examples.
The authors wish to increase the confidence of engineers using
adhesive bonding in load-bearing applications by the information and
experience presented. With increasing experience of adhesives en
gineering, design will become more elegant as weH as more fitted to its
products.
R. D. ADAMS
W.C.WAKE
Acknowledgements
Acknowledgements are necessarily and gladly made by the authors for
help, advice and criticism to Dr J. A. Harris of Bristol University, Dr
A. J. Kinloch of the Ministry of Defence (PERME), Waltham Abbey,
and Dr P. Poole of the Royal Aircraft Establishment, Farnborough.
Former colleagues and students have contributed in the past to the
work on which this book is largely based, in particular Drs N. A.
Peppiatt, J. Coppendale and A. D. Crocombe.
The publisher joins with the authors in thanking those individuals
and Journals listed below for permission to use diagrams and photo
graphs which have either appeared elsewhere or are modifications of
published material:
Adhäsion (Berlin) for Figs 99-101, 110 and 111 from papers by the
late Prof. Dr-Ing. A. Matting.
K. W. Allen and J. Adhesion for Figs 107 and 108.
Dr W. Althof and Metall (Berlin) for Figs 116, 119 and 120.
Dr H. A. Burgman and J. Appl. Polym. Sei. for Fig. 118.
Dr J. Cotter and J. Adhesion for Fig. 115.
Prof. Dr-Ing. F. Eichhorn and Adhäsion for Fig. 114.
Engineering Sciences Data Unit Publication, ESDU 79016 for Fig.
33.
Dr L. J. Hart-Smith for Figs 32, 34-36 and the Douglas Aircraft
Co., for Figs 37 and 38.
The Institution of Civil Engineers for Figs 54 and 56.
J. Adhesion for Figs 27-30, 69 and 87.
J. Strain Anal. for Figs 10, 13-23 and 63-68.
Dr H. Schonhorn and J. Appl. Polym. Sei. for Fig. 92.
Dr M. E. R. Shanahan and The City University for Fig. 98.
Dr B. Wargotz and J. Adhesion for Fig. 102.
Figures 1 and 124 are Crown Copyright and Fig. 109 is based on data
supplied by the Royal Aircraft Establishment, Farnborough.
vi
Contents
Preface v
Acknowledgements . vi
Chapter 1. INTRODUCrION 1
Joint Configurations: Lap-shear Joints, Butt Joints,
Fillets. Metals and Other Constructional Materials.
The Decision to Use Adhesive Bonding. The Balance
of Advantages and Disadvantages
Chapter 2. THE NATURE AND MAGNITUDE OF
STRESSES IN ADHESIVE JOINTS 14
Introduction: Reality, Methods of Mathematical
Analysis. The Single Lap Joint: Linear Elastic
Analysis, Volkersen's Analysis, The Analysis of Go-
land and Reissner, Effect of Bending in a Double-lap
Joint, Volkersen's Second Theory, Later Work. The
Single-lap Joint-End Effects: Reduction of Stress
Concentrations. The Single-Iap Joint-Elasto-plastic
Analysis. The Effect of Adherend Shape-Scarfed,
Bevelled and Stepped Adherends. Composite Ma-
terialls. Tubular Joints. Butt Joints. The Use of Joints
in Design: Lap Joints, Tubular Joints, T -joints,
Corner Joints, Butt Joints, Stiffeners, Doublers,
Assembly
Chapter 3. STANDARD MECHANICAL TEST PROCE-
DURES .................. 115
Destructive Testing: Tests with Thin Sheet
Adherends, Tests for Properties of Adhesives. Non-
vii
viii CONTENrS
destructive Testing: Nature of Defects, Tests Carried
Out Before Bonding, Post-bonding and In-service
Testing
Chapter 4. THE GENERAL PROPERTIES OF
POLY MERIC ADHESIVES . . . . . 143
Polymer Structures: Unsaturation. Mixed Adhesives.
Properties and Temperature: The Glass Transition
Temperature, Decomposition Temperature, Melting
Temperature, The Deformation of Adhesive Poly
mers by Stress, Viscoelasticity, The Modulus of an
Adhesive, Poisson's Ratio, Strength Properties of
Adhesive Polymers, Yie1ding Stresses of Polymers,
Failure Modes After Yie1ding, Creep, Failure without
Yielding-Brittle Fracture, Crazing, Coefficient of
Thermal Expansion, Resistance to Deterioration
Chapter 5. FACTORS INFLUENCING THE CHOICE
OF ADHESIVE .............. 175
Interaction with Substrate. Structural Adhesives for
Metals: Check-list for Structural Metal Adhesives
Used at Temperatures up to 70°C, The Advantage of
Supported Filmic Adhesives (Tapes'), Unsupported
Films, Liquids and Pastes, Infiuence of Metal of
Adherend, High Temperature Metal-Metal Adhe-
sion. Structural Adhesives for Wood: Check-list for
the Use of Structural Wood Adhesives. Structural
Adhesives for Mixed Constructions: Metal-Wood
Structures, Metal-reinforced Plastics Structures.
Choice of Adhesives for Semi-structural Use: Check-
list for Adhesives for Semi-structural Use
Chapter 6. SURFACE PREPARATION 218
Metals. Wood. Concrete. Glass or Carbon-fibre
Reinforced Plastics. Shot, Sand or Grit Blasting.
Solvent Degreasing or Wiping. Chemical Etching:
Aluminium, Ferrous Metals, Titanium, Other Metals.
Priming Layers: Primers as Coupling Agents
Chapter 7. SERVICE LIFE 237
The Creep of Adhesive Joints. Time-to-failure
(Under Static Loading). Cyc1es-to-failure: Influence
CONTENTS IX
of Temperature, Infl.uence of Test Frequency, In
f1.uence of Amplitude, Infl.uence of Moisture. Effects
of Temperature Change on Joint Strength. Service
Life as Indicated by Climatic Exposure Trials
Chapter 8. APPLICAT IONS 271
Aircraft, Anchorages. Bridges. Carriages. Cars.
Decking. Furniture. Glass Reinforced Plastics. Heli
copters. He1icopter Blades. Hovercraft. Lamp Posts.
Magnets. PABST. Rollers. Segmental Construction.
Ski Constructions. Telephone Kiosks. Yachts
Reterences . 283
Appendix: Standard American and UK Specijications tor
Adhesion Tests. . . . . . . . . . . . . . 293
Author Index 299
Subject Index 303
Chapter 1
Introduction
An engineer designs or builds machines and structures. This book is
about the design and building of structures using a particular method
of construction chosen from the several, diverse methods available.
Structures built from metallic components can have these components
assembled by bolting, riveting or other forms of mechanical fastening,
by welding, by the related processes of brazing or soldering, or an
organic adhesive can be used to bond the components to each other.
One of the few remaining alternatives is to machine the structure from
a solid block as astatue is sculpted from a monolith. Training and
experience combine to teach the engineer to marry design and method
of assembly when considering the various me ans of mechanical fasten
ing, distinguishing them not only from each other but also from the
alternatives of welding or brazing. His training is less able to cope with
the use of adhesives, with essential choices between the many types
available and with the design approach appropriate to structures
assembled with them. Subsequent chapters of this book have been
written to assist the training of engineers in this extension of their
expertise, to give practising engineers an aide-memoire of design
criteria with adhesive properties and as a bonus, to help the adhesives
technologist in assessing the needs of the engineering industry.
Apart from structural uses, adhesives are used for surfacing either by
the adhesives material itself providing the finished surface or by its use
for attaching ceramic tiles or brick slips. They are also used as sealants
for curtain walls and for sealing the seams of liquid containers from the
small tin can to the integral fuel tanks of large aircraft. Neither the
surfacing nor the sealing use of adhesives will feature, other than
trivially, in these pages. Also excluded is the use of adhesives sub-
1
2 STRUCTURAL ADHESIVE JOINTS IN ENGINEERING
stances as aggregate binders in 'resin concretes', which may be re
garded as structural material in their own right and have been recently
discussed in the context of adhesion (Hewlett and Shaw, 1977). Glass
and carbon fibre reinforced plastics are important structural materials,
the strength of which depends on the performance of the polymer
matrix as an adhesive but, once again, it is the material rather than its
manufacture which is the concern of the structural engineer. Fastening
or bonding structural components made of GRP or CFRP is a focus of
attention and features in Chapters 3 and 5-8.
This brief catalogue of inclusions and exclusions may be briefly
summed up by stating that the engineer, in building structures, is
concerned about the transmission and accommodation of stresses. This
book discusses the behaviour of adhesives, and joints made with them,
when stresses of significant magnitude are imposed, and how such
joints are best made.
JOINT CONFIGURATIONS
Joint design is dependent upon the nature of the materials to be joined
as weIl as on the method of joining. The first cast iran bridge, at
Ironbridge, Salop, was made by casting massive half-arches and as
sembling the structure with mortise and tenon joints, with fit-on parts
and tapered pegs. This mode of construction was the only one known
to the designer, a mode used for timber structures. The only conces
sion to the new structural material was in the use of large scale, single
piece, curved members. Rolled bars of T - and L-sections did not
become available until after the Napoleonic wars and the first I-beams,
for light loading only, were made in Paris in 1847 (Hamilton, 1958).
Heavy I-beams only became available in 1860 after the invention of
mild steel. Fastening was originally by slotting a circular cylinder, cast
as an integral part of the beam, over a cylindrical column, cast with a
retaining lip, but fish plates and bolting were introduced at an early
stage.
The design of joints in wooden structures similarly underwent
changes through the centuries when structural iron became available.
Mortised joints, at best half the strength of the wooden tie-beams
transmitting a puH, were avoided in large structures. In the eighteenth
century iron work was introduced, and forged straps secured by gib
and cotter, enabled loads to be suspended via wooden tie bars (Hamil
ton, 1958). Tie bars were also lengthened by various designs of scarfed
joints secured with fish plates and bolts. These impravements in joint