Fatigue Failure of Textile Fibres Edited by Mohsen Miraftab


Fatigue Failure of Textile Fibres
Edited by Mohsen Miraftab

Fatigue failure of textile fibres


Contributor contact details ix
Woodhead publishing in textiles xi

Part I: Principles and types of fatigue in textile fi bres 1
1 Basic principles of fatigue 3
M Miraftab, University of Bolton, UK
1.1 Introduction 3
1.2 Fibre fatigue 4
1.3 Fatigue data representation 6
1.4 Future trends 7
1.5 References 8
2 Tensile fatigue of textile fi bres 10
A Bunsell, Ecole des Mines de Paris, France
2.1 Introduction 10
2.2 Principles of tensile fatigue 11
2.3 The fatigue failure of thermoplastic textile fibres produced by melt spinning 13
2.4 Mechanisms involved in fi bre fatigue 19
2.5 Fibre fatigue failure at temperature and in structures 23
2.6 Tensile properties of organic fi bres 27
2.7 Fatigue of liquid crystal fi bres 29
2.8 High modulus polyethylene fi bres 31
2.9 Conclusions 32
2.10 References 33
3 Flex fatigue of textile fi bres 34
M Miraftab, University of Bolton, UK
3.1 Introduction 34
3.2 Methods of fl exing fi bres 35
3.3 Kink bands 38
3.4 Effect of temperature on fl ex fatigue 40
3.5 Effect of temperature and humidity on fl ex fatigue 44
3.6 Theoretical aspects of fl ex fatigue 49
3.7 References 52
4 Torsional fatigue failure in fi bres 53
B S Wong and X Wang, Nanyang Technological
University, Singapore
4.1 Introduction: principles of torsional fatigue 53
4.2 Types of fi bres affected 53
4.3 Methods of testing torsional fatigue 53
4.4 Factors affecting fi bre torsional fatigue 56
4.5 Ways of reducing torsional fatigue 71
4.6 Sources of further information and advice 72
4.7 References 72
5 Biaxial rotation fatigue in textile fi bres 73
B S Wong and X Wang, Nanyang Technological
University, Singapore
5.1 Introduction: principles of biaxial rotation fatigue 73
5.2 Types of fi bres which can be tested 74
5.3 Methods of testing biaxial fatigue 74
5.4 Factors affecting biaxial fatigue 75
5.5 Rotation over a pin (single end drive) 82
5.6 New developments and future trends 90
5.7 Advice on ways of reducing biaxial fatigue 90
5.8 Conclusions 91
5.9 References 91

Part II: Factors affecting fatigue life and fatigue case studies 93
6 Effect of structure–property relationships on fatigue failure in natural fi bres 95
L Wang, RMIT University, Australia and X Wang,
Deakin University, Australia
6.1 Introduction 95
6.2 Natural fi bre structure and morphology 97
6.3 Fatigue of natural fi bres 99
6.4 Methods of controlling fatigue in natural fi bres 121
6.5 Conclusions 129
6.6 References 129
7 Effect of textile processing on fatigue 133
J Militky and S Ibrahim, Technical University of
LIBEREC, Czech Republic
7.1 Introduction 133
7.2 Fatigue of materials and structures 134
7.3 Fatigue of textile structures 145
7.4 Prediction of fatigue during wearing 163
7.5 Conclusions 165
7.6 Acknowledgements 165
7.7 References 165
8 Environmental aspects of fatigue 169
K Slater, University of Guelph, Canada
8.1 Introduction: aspects of importance 169
8.2 Effects of environment on fatigue fracture 170
8.3 Effects of fatigue fracture on the environment 178
8.4 Overcoming environmental effects 180
8.5 Future trends 182
8.6 References 185
9 Fatigue of polymer-matrix textile composite materials 188
Y Gowayed, Auburn University, USA
9.1 Introduction 188
9.2 Experimental evaluation of fatigue response 190
9.3 Modeling of fatigue behavior 194
9.4 Conclusions 199
9.5 References 199
10 Fatigue damage in structural textile composites: testing and modelling strategies 201
W Van Paepegem, Ghent University, Belgium
10.1 Introduction 201
10.2 Materials 202
10.3 Fatigue testing methods 205
10.4 Typical fatigue damage in structural textile composites 218
10.5 Modelling strategies for fatigue damage in textile composites 223
10.6 Future trends and challenges 228
10.7 Sources of further information and advice 230
10.8 References 231
Index 242

Basic principles of fatigue
University of Bolton, UK

Abstract: The notion of fatigue phenomena and their distinctive difference from other forms of failure is briefl y explained in this chapter. Different methods by which fatigue failures are manifested and collected data are represented and discussed. Effects of physical and environmental conditions on ultimate failure forms are highlighted and finally the need for further research in emerging areas and application spectrum of ultra-fi ne fi bres is stated.

Key words: failure, fatigue, tensile, survival diagram.

1.1 Introduction
Flexibility and versatility of textile materials ultimately lead to failure of one kind or another. Failure, as in appearance of holes in a garment or edge fraying in a work uniform, has been the subject of much study and specialised debate in the past. However, their importance as an engineering malfunction has been substantially marginal due to their limited use and practical requirements. With the advent of technical and performance textiles, where durability and material resilience override fabric appearance and normal wear and tear, an in-depth understanding of fracture and failure of textile materials has become an essential ingredient in design and manufacture of textile-based products.

To understand fabric or structural failure, a thorough investigation trailing back to the most fundamental level, i.e. ‘fi bres’ representing the building blocks of any textile-based assembly must be undertaken. Fibres’ innate or adopted specifications determine fi bre/yarn strength, uniformity, fl exibility, durability and ultimately product performance. It is therefore only logical to try to understand failure from a single fibre point of view. Because of the fineness of fi bres, it is possible to impose on the material very fast and controlled sequences of temperatures, chemical environment, stress and so on. This enables the development of the fine structure of the material to be closely engineered in a way which is not possible with materials in bulk. Fibres can be heated and cooled at 1000 ºC/sec or faster, whereas in bulk materials, the limits of thermal conductivity slow down changes, cause differences between different parts of the material and builds in internal stresses. A given material can be made in a higher strength form as a fi bre than as a large piece.(1)

Application of such advanced engineering techniques would inevitably affect the economics of production and the subsequent marketing potential. Durability and resistance to large deformation would therefore be a fundamental requisite of any fi bre assembly. Hence the study of ‘fatigue’ as possibly the single most important cause of fi bre failure has become vital. The term ‘failure’ is an umbrella defi nition of what fi bre breakdown is and does not differentiate between different modes and causes of failure. Most commonly perceived types of failures are those caused by pulling or over-stretching a fi bre, yarn or a fabric to the point of breakdown, i.e. when these materials undergo tensile failures. In the literature much investigative study has been devoted to these kinds of failures relating to both natural and man-made fi bres. However, materials can also fail by rubbing or frictional interaction with the same or different media causing what is commonly referred to as breakage due to abrasion. Abrasion itself is a well-understood phenomena where many factors including temperature, humidity, type and nature of materials infl uence its mode and form of failure. A third and maybe the least obvious type of failures are those caused by repeated or cyclic action of a force that is always far below the normal force required for stretch or tensile breaks. These are failures induced by the phenomena of fatigue.

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