Irving / Soutis Polymer Composites in the Aerospace Industry

1. Auflage 2014
ISBN: 978-0-85709-918-1
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, Band 50, 536 Seiten

Reihe: Woodhead Publishing Series in Composites

Polymer composites are increasingly used in aerospace applications due to properties such as strength and durability compared to weight. Edited by two leading authorities in the field, this book summarises key recent research on design, manufacture and performance of composite components for aerospace structures. Part one reviews the design and manufacture of different types of composite component. Part two discusses aspects of performance such as stiffness, strength, fatigue, impact and blast behaviour, response to temperature and humidity as well as non-destructive testing and monitoring techniques.

Autoren/Hrsg.

Irving, P. E.

Soutis, Costas

Inhaltsverzeichnis

1;Front Cover;1
2;Related titles;3
3;Polymer Composites in the Aerospace Industry;4
4;Copyright;5
5;Contents;6
6;List of contributors;12
7;Woodhead Publishing Series in Composites Science and Engineering;14
8;1 - Introduction: engineering requirements for aerospace composite materials;18
8.1;1.1 Introduction;18
8.2;1.2 Analysis and design;21
8.3;1.3 Manufacturing techniques;26
8.4;1.4 Applications in aircraft construction;28
8.5;1.5 Conclusion;33
8.6;References;34
9;Part One -
Design and manufacture of composite components for aerospace structures;36
9.1;2 - Modelling the structure and behaviour of 2D and 3D woven composites used in aerospace applications;38
9.1.1;2.1 Introduction;38
9.1.2;2.2 Architecture of a woven unit cell;40
9.1.3;2.3 Stiffness modelling: method of inclusions;49
9.1.4;2.4 Stress and strength modelling: finite element (FE) analysis;56
9.1.5;2.5 Conclusion;63
9.1.6;Acknowledgement;64
9.1.7;References;64
9.2;3 - Manufacturing processes for composite materials and components for aerospace applications;70
9.2.1;3.1 Introduction;70
9.2.2;3.2 Key property and process requirements;71
9.2.3;3.3 Prepreg/autoclave processes;73
9.2.4;3.4 Filament winding;76
9.2.5;3.5 Automated prepreg processes: automated fibre placement and automated tape layup;78
9.2.6;3.6 Resin-infusion processes;80
9.2.7;3.7 Process monitoring;89
9.2.8;3.8 Conclusions;90
9.2.9;References;90
9.3;4 - Buckling and compressive strength of laminates with optimized fibre-steering and layer-stacking for aerospace applications;94
9.3.1;4.1 Introduction;94
9.3.2;4.2 Elastic properties of laminates;95
9.3.3;4.3 Buckling analysis;99
9.3.4;4.4 Buckling optimization of straight fibre laminates;101
9.3.5;4.5 Variable angle fibres using continuous tow shearing;101
9.3.6;4.6 Compression after impact and damage tolerance;106
9.3.7;4.7 Conclusion;112
9.3.8;Acknowledgements;113
9.3.9;References;113
9.3.10;4. Appendix: glossary;114
9.4;5 - Manufacturing defects in composites and their effects on performance;116
9.4.1;5.1 Introduction;116
9.4.2;5.2 Defects in composite materials;116
9.4.3;5.3 Modelling with defects;122
9.4.4;5.4 Implications on cost-effective manufacturing;123
9.4.5;5.5 Mechanics-based analysis of defects;124
9.4.6;5.6 Summary;129
9.4.7;References;130
10;Part 2 Composite performance in aerospace structure design;132
10.1;6 - Modeling the stiffness and strength of aerospace structural elements;134
10.1.1;6.1 Introduction;134
10.1.2;6.2 Definition of structural elements;134
10.1.3;6.3 Modeling approaches;136
10.1.4;6.4 Woven composite materials;160
10.1.5;6.5 Modeling effect of anomalies;162
10.1.6;6.6 Future trends;164
10.1.7;6.7 Sources of further information and advice;166
10.1.8;References;167
10.1.9;6. Appendix: glossary;169
10.2;7 - Fatigue of fiber reinforced composites under multiaxial loading;172
10.2.1;7.1 Introduction;172
10.2.2;7.2 Fatigue behavior of continuous fiber composites under multiaxial loading;174
10.2.3;7.3 Fatigue behavior of continuous fiber reinforced composites under multiaxial loading;176
10.2.4;7.4 Multiaxial fatigue ratio;186
10.2.5;7.5 Fatigue life prediction criteria;187
10.2.6;7.6 Comments on life prediction criteria and damage mechanics;198
10.2.7;7.7 Conclusions;201
10.2.8;References;201
10.2.9;7. Appendix: symbols;206
10.3;8 - Fracture mechanics characterization of polymer composites for aerospace applications;208
10.3.1;8.1 Introduction;208
10.3.2;8.2 Applications of fracture mechanics of fibre-reinforced polymer-matrix (FRP) composites in aerospace;211
10.3.3;8.3 Fracture mechanics test methods for FRP composites;213
10.3.4;8.4 Fracture mechanics test data for selected FRP composites;218
10.3.5;8.5 Fracture mechanics testing of non-unidirectional FRP composites;225
10.3.6;8.6 Fracture mechanics testing under aerospace environmental conditions;231
10.3.7;8.7 Conclusions and future trends;235
10.3.8;Acknowledgements;237
10.3.9;References;238
10.3.10;8. Appendix: glossary;246
10.4;9 - Impact, post-impact strength and post-impact fatigue behaviour of polymer composites;248
10.4.1;9.1 Introduction;248
10.4.2;9.2 Nature of damage;249
10.4.3;9.3 Residual strength;252
10.4.4;9.4 Post-impact fatigue behaviour of polymer composite laminates;254
10.4.5;9.5 Prediction of impact damage extent, residual strength and post-impact fatigue;264
10.4.6;9.6 The damage-resistant structure: designing against impact and fatigue;269
10.4.7;9.7 Damage tolerance;270
10.4.8;9.8 Conclusions and future trends;272
10.4.9;References;273
10.5;10 - Design and testing of crashworthy aerospace composite components;278
10.5.1;10.1 Introduction;278
10.5.2;10.2 Crashworthy design concepts for aircraft structures;280
10.5.3;10.3 Design of composite structural elements under crash loads;286
10.5.4;10.4 Design and crash test of composite helicopter frame structure;295
10.5.5;10.5 Conclusions and future trends;304
10.5.6;Acknowledgements;306
10.5.7;References;307
10.6;11 - Design and failure analysis of composite bolted joints for aerospace composites;312
10.6.1;11.1 Introduction;312
10.6.2;11.2 Finite element model;318
10.6.3;11.3 Analysis of single-bolt joints;319
10.6.4;11.4 Analysis of multi-bolt joints;330
10.6.5;11.5 Failure analysis of joints;336
10.6.6;11.6 Future trends;345
10.6.7;11.7 Conclusions;347
10.6.8;11.8 Further sources of information;347
10.6.9;References;348
10.7;12 - The response of aerospace composites to temperature and humidity;352
10.7.1;12.1 Introduction;352
10.7.2;12.2 Moisture absorption;353
10.7.3;12.3 Moisture sensitivity of matrix resins;358
10.7.4;12.4 Mechanism of moisture retention in aerospace epoxies;361
10.7.5;12.5 Anomalous effects;366
10.7.6;12.6 Thermal spiking;367
10.7.7;12.7 Thermo-mechanical response of resins;368
10.7.8;12.8 Effect of moisture on composite performance;370
10.7.9;12.9 Fibre-dominated properties;375
10.7.10;12.10 Nonaqueous environments;379
10.7.11;12.11 Composite unidirectional properties;380
10.7.12;12.12 Conclusions;384
10.7.13;References;385
10.8;13 - The blast response of composite and fibre-metal laminate materials used in aerospace applications;388
10.8.1;13.1 Introduction;388
10.8.2;13.2 Characteristics of explosions in air;389
10.8.3;13.3 Paradigms of blast protection;391
10.8.4;13.4 Explosion loading of fuselage structures;392
10.8.5;13.5 The blast performance of plain composites;392
10.8.6;13.6 The blast performance of multilayered systems;399
10.8.7;13.7 Conclusions;405
10.8.8;References;405
10.9;14 - Repair of damaged aerospace composite structures;410
10.9.1;14.1 Introduction;410
10.9.2;14.2 Assessment of repair and non-destructive tests;412
10.9.3;14.3 Repair;415
10.9.4;14.4 Typical repair procedure;418
10.9.5;14.5 Analysis of repair;422
10.9.6;14.6 Conclusion and future trends;427
10.9.7;References;428
10.10;15 - Nondestructive testing of damage in aerospace composites;430
10.10.1;15.1 Introduction;430
10.10.2;15.2 Types of composite damage;430
10.10.3;15.3 Damage in sandwich composites and in adhesive joints;438
10.10.4;15.4 NDT, NDI, and NDE methods for polymer composite structures;440
10.10.5;15.5 Probability of detection;445
10.10.6;15.6 Visual and tap testing;446
10.10.7;15.7 Ultrasonic testing;446
10.10.8;15.8 Thermography;453
10.10.9;15.9 Shearography;456
10.10.10;15.10 Radiography;457
10.10.11;15.11 Electromagnetic methods;460
10.10.12;15.12 Bond inspection;461
10.10.13;15.13 Summary and conclusions;462
10.10.14;References;462
10.11;16 - Structural health monitoring (SHM) of aerospace composites;466
10.11.1;16.1 Introduction;466
10.11.2;16.2 Conventional resistance strain gauges;466
10.11.3;16.3 Fiber optics sensors;467
10.11.4;16.4 Fiber Bragg grating (FBG) sensors;470
10.11.5;16.5 Piezoelectric wafer active sensors (PWAS);473
10.11.6;16.6 Electrical properties sensors;478
10.11.7;16.7 SHM systems;479
10.11.8;16.8 Local-area active sensing with electromechanical impedance spectroscopy;506
10.11.9;16.9 Active sensing SHM: electrical methods;508
10.11.10;16.10 Direct methods for impact damage detection;516
10.11.11;16.11 Conclusions;518
10.11.12;References;518
11;Index;526

Leseproben

2

Modelling the structure and behaviour of 2D and 3D woven composites used in aerospace applications

D.S. Ivanov1,  and S.V. Lomov2     1University of Bristol, Bristol, UK     2KU Leuven, Leuven, Belgium

Abstract

The chapter starts from description of geometrical models of 2D and 3D woven fabrics, with an aim of creation of meso-level (textile unit cell) finite element (FE) models, and proceeds to micromechanics of woven composites, based on the method of inclusions/Mori-Tanaka homogenisation and FE analysis of the stress–strain state of the unit cell. Special attention is paid to geometrical consistency of the FE models. CDM-type damage model is presented and an example of FE modelling of a woven composite is given.

Keywords

Damage; Homogenisation; Internal geometry; Models; Woven composites

2.1. Introduction

Textile and, more narrowly, woven composites are an important class of high performance composite materials used in aerospace. In the production of composite parts, the use of textile reinforcements brings benefits in handability of the fabrics and in easier applicability of closed-mould processes. In performance, due to interlacing of yarns in textile, damage tolerance is improved in comparison with unidirectional cross-ply laminates, even if stiffness and strength are to a certain extent compromised because of yarn crimp, inherent for textile reinforcements. For the general introduction in the field of textile reinforcements and textile composites, as well as modelling of a dry textile behaviour during forming, the reader is referred to the classical works [1–3], recently published books [4–6], online encyclopaedia [7] and proceedings of the latest TexComp conference series [8,9], which can serve as a starting point for studying of the current literature.

Modelling of textile composites may be seen as an integrated simulation process that involves two integration paths. On one hand, the behaviour of a composite (be it in processing or in performance) is determined by its reinforcement fibrous architecture. This dictates the necessity to develop a scale integration of the models: from microscale, representing the local behaviour of dry or impregnated fibrous yarns and plies, through meso-scale, corresponding to a unit cell (representative volume element, RVE) of textile reinforcement up to macroscale analysis of a composite part. On another hand, processing of a composite (involving reinforcement deformation in draping, its impregnation and the material consolidation) defines the final reinforcement architecture, as well as its defects (voids and fibre misplacement). Hence, the performance models on all the scale levels should be integrated with process models. Figure 2.1 illustrates this integration of models.

This chapter is dedicated to meso-level modelling of internal architecture, mechanical behaviour and damage of 2D and 3D woven composites, focusing on meso-level models of a textile reinforcement unit cell. The chapter is intended to represent the personal views and approach of the authors in the context of the state of the art rather than to be a review of the current literature and the history of the subject; therefore, the reference list is by no means exhaustive.

Figure 2.1 Integration of textile composite models.

To adequately represent property-structure dependencies between the reinforcement woven architecture and mechanical behaviour of the composite, it is necessary first to introduce a generic way to describe the internal geometry of a woven unit cell. The geometrical models and algorithms of weave coding are general enough to cover all 2D and 3D weaves used as composite reinforcements. Then two types of mechanical models of a woven composite are presented. Calculation of the composite stiffness can be based, of course, on a finite element (FE) model of the unit cell and a rigorous asymptotic homogenisation theory. However, less rigorous homogenisation, employing representation of the unit cell with an assembly of Eschelby inclusions that are subject to Mori-Tanaka homogenisation scheme, give quite adequate predictions of the full stiffness matrix of the composite even for complex weaves, accounting for peculiarities of the architecture better than simple iso-strain orientation averaging. When details of the stress–strain distribution in the composite, damage behaviour and ultimate strength of the composite is the simulation goal, full representation of the geometry and use of FEs becomes indispensable. The chapter explores both approaches: inclusion and meso-FE models.

2.2. Architecture of a woven unit cell

2.2.1. 2D and 3D weave topology and geometry

The mathematical description of the weave topology is the first necessary step in modelling of the architecture of the unit cell.1 The matrix weave coding for 3D fabrics, described here, was proposed in [10,11] and is implemented in software WiseTex [12] with GUI for definition and editing the weave (the images in this chapter are produced using this software). Note that this approach differs from the approach used in [13–15], who aim on technological issues as, for example, the shedding lifting plan for a loom. In [16] the specific matrix coding is applied to produce 3D images of a fabric, and their approach is closer to the one described here.

Consider a warp-interlaced 3D weave (rather ‘multilayered’ weave) – Figure 2.2. The topological coding of a multilayered weave is based on the warp yarns paths. The i-th warp path is coded by a sequence of intersection levels wij – denoting either the index number of the weft layer situated above the warp yarn in its intersection with the jk-th weft row, or 0, if the warp yarn lies on the face of the fabric. Let a fabric have L weft layers. Then warp in intersections with the weft can occupy L+1 levels, level 0 corresponding to the face of the fabric, level L to the back of the fabric. Each warp can be now coded as a sequence of level codes, and the entire weave as a matrix, as shown in Figure 2.2. The matrix coding of a one-layer weave also represents a checkerboard pattern, if level 0 were identified with a black square, level 1 with a white square as in Figure 2.2(b). In the pattern shown in Figure 2.2(a), all the warps are situated side by side. It is very often in composite reinforcements that warps also are layered, as shown in Figure 2.2(c). Paths of the warps in this case also can be coded as a sequence of level codes. To represent their layered positioning, a notion of warp zones is introduced. A warp zone is a set of warp yarns layered one over another. The yarns going through the thickness of a fabric are called Z-yarns (e.g. yarn 1 in Figure 2.2(c)).

Figure 2.2 Matrix coding of a multilayered weave:

(a) building the matrix: weft layers are shown with thin white lines, intersection levels – with thin black lines; (b) warp in zones; (c) angle interlock; (d) ‘missing weft’ algorithm.

Once a weave coding is defined, an analysis of the weave matrix allows answering questions about mutual positions of the yarns. Consider a warp yarn between two intersections with weft. Which weft yarns is it interacting with in these intersections? What is its position vis-à-vis these yarns? An answer to these questions is evident for one-layer weave, but for multilayered weaves it needs analysing the weave code. Knowing these answers allows definition of interactions between warp and weft, which is needed for building a geometrical model of the unit cell based on mechanics of these interactions, and definition of contacts between the yarn needed for creation of meso-level FE models.

Consider a warp yarn first, e.g. the first warp yarn in Figure 2.2(a). Its level codes are {wi}={0,2,4,2}.The yarn can be subdivided into crimp intervals, which constitute a part of the yarn between two intersections. At the first crimp interval, the yarn is supported (interacts with at the ends of the interval) with weft yarns in the layers 11=1 and 12=2 (the subscript gives the number of the crimp interval, the superscript identify one of its ends). The yarn is situated above its supporting weft at the left end of the crimp interval and below the supporting weft at the right end.

To construct the same description for a weft yarn, the intersection codes and parameters of crimp intervals of warp are used. Consider a weft yarn i at layer l. First, looking up the lists of crimp interval parameters, find the first warp that has in its lists 11=l or i2=l (i.e. supported by the weft yarn i at layer l). This would be the left end of the first crimp interval on the weft yarn. The support warp number is thus found, and the position sign of the weft would be inverse to the position sign of the warp. Then find the next warp yarn supported by the weft (l,i). This would be the right end of the first crimp interval on the weft yarn, and the left end of the second crimp...