The Structural Integrity of Carbon Fiber Composites (eBook)

Dr. Peter Beaumont, University of Cambridge, investigates mechanical properties and engineering performance of a wide range of materials systems for applications in aerospace, automotive research, power generation, electronics, and medicine. Professor Costas Soutis, University of Manchester, investigates compressive response of composite plates under uniaxial and bi-axial static and fatigue loading, impact and post-impact compressive strength, repair of composite laminates and structures, crush energy absorption, and quantitative non-destructive evaluation of composites.

Preface 5
Acknowledgements 8
Contents 9
Part I 13
1 50 Years in Carbon Fibre, 60 Years in Composites 14
1.1 A Perspective: 1956–2016 14
1.2 Vibration and Damping in Composites 18
1.3 Non-destructive Testing and Quality Assurance for Components Made Using CFRP 24
1.4 Effect of Aggressive Environments on CFRP Performance 29
1.5 The Special Problems of Adhesive Bonding with CFRP 30
1.6 Final Remarks, but Not “Conclusions” 32
References 36
2 `But How Can We Make Something Useful Out of Black String?' The Development of Carbon Fibre Composites Manufacturing (1965 –2015) 40
2.1 Introduction 40
2.2 Understanding Prepreg Layup 41
2.2.1 Background and Early History 41
2.2.2 The Early Development of an Understanding of Reinforcement Deformation 44
2.2.3 Drape Modelling 46
2.2.4 Understanding Manufacturability 48
2.3 Resin Transfer Moulding 55
2.4 Defects and Variability in Composites Manufacturing 59
2.4.1 Introduction 59
2.4.2 In-Process Inspection and Defect Identification 60
2.4.3 Dimensional Fidelity 61
2.5 Conclusions, Modelling and Predictive Tools, Current Status and Future Work 63
References 66
3 Boron Fiber to Carbon Fiber 69
3.1 Introduction 69
3.2 NASA-Virginia Tech Composites Program 70
3.3 Boron Fiber Composites 70
3.4 Fiber Property Comparisons 74
3.5 Carbon Composite Test Methods 76
3.5.1 Tension 76
3.5.2 Compression 77
3.5.3 Shear 78
3.6 Free Edge Effects 78
3.7 Concluding Remarks 79
References 80
4 Serendipity in Carbon Fibres: Interfaces and Interphases in Composites 81
4.1 Introduction 81
4.2 High-Strength Carbon Fibres from PAN Precursors 82
4.3 Manufacturing Process for Carbon Fibres 86
4.3.1 The Carbon Fibre Manufacturing Process 86
4.4 The Interface in CFRP 89
4.4.1 CF Surface Chemistry 89
4.4.1.1 High-Strength (HS) Carbon Fibre 89
4.4.1.2 High-Modulus (HM) Carbon Fibre 89
4.4.2 Assessment Interfacial Strength in Composites 94
4.4.2.1 Interlaminar Shear Strength (ILSS) 94
4.4.2.2 The Fragmentation Test 97
4.4.3 The Role of Sizing in Interphase Formation 100
4.4.4 Designing Interphases for Improved Properties 103
4.5 Conclusions 105
References 106
Part II 108
5 Nano-Engineered Hierarchical Carbon Fibres and Their Composites: Preparation, Properties and Multifunctionalities 109
5.1 Introduction 109
5.2 Preparation of Hierarchical CF/CNT Composites 110
5.3 Properties of Hierarchical CF/CNT Composites 113
5.4 Multifunctionalities of Hierarchical CNT/CF Composites 117
5.5 Conclusions and Outlook 121
References 122
6 Nano-engineered Carbon Fibre-Reinforced Composites: Challenges and Opportunities 125
6.1 Introduction 125
6.2 Composites with CNT-Reinforced Matrices 128
6.3 Composites with CNT-Reinforced Interfaces 131
6.4 Modelling of Nano-engineered Fibre-Reinforced Composites 134
6.5 Composites with CNT Fibres 136
6.6 Concluding Remarks 138
References 139
7 A Nano-micro-macro-multiscale Model for Progressive Failure Prediction in Advanced Composites 144
7.1 Introduction 144
7.2 Atomistic Level Analysis Using Molecular Dynamics (MD) 148
7.2.1 Materials Failure Simulation Using Molecular Dynamics (MD) 151
7.2.1.1 Strength-Based Failure Modeling 152
7.2.1.2 Fracture-Based Failure Modeling 154
7.3 Micromechanics Level Analysis Using the Generalized Method of Cells 166
7.4 Three-Dimensional Ply-Level Analysis Using Finite Element Analysis and Multiscale Coupling 170
7.5 Closing Remarks 172
References 174
8 Carbon Fibre-Reinforced Polymer Laminates with Nanofiller-Enhanced Multifunctionality 177
8.1 Introduction 177
8.2 Enhanced Mechanical Properties 179
8.2.1 Typical Characterisation Methods for FRP 179
8.2.1.1 Interlaminar Fracture Toughness 179
8.2.1.2 Compression-After-Impact (CAI) Strength 180
8.2.1.3 Interlaminar Shear Strength 180
8.2.2 Nanofiller-Enhanced Mechanical Properties 180
8.2.2.1 Carbon Nanotubes (CNTs) 181
8.2.2.2 Nanofibres 182
8.2.2.3 Organoclay 183
8.2.2.4 Nanosilica and/or Rubber 184
8.2.2.5 Other Fillers 184
8.2.3 GIC, GIIC and GIIC/GIC 185
8.2.4 Interlaminar Shear Strength of Different Nanofiller-Enhanced CFRP Composites 185
8.2.5 CAI Strength 187
8.2.6 Fatigue Behaviours 190
8.3 Electrical Conductivity 193
8.4 Thermal and Thermomechanical Aspects 193
8.5 Further Exploitation 196
8.6 Conclusions and Remarks 199
References 199
9 Analysis Models for Polymer Composites Across Different Length Scales 204
9.1 Introduction 204
9.2 Computational Micro-Mechanics 205
9.2.1 RVE Generation 206
9.2.2 Constitutive Models for the Resin, Fibers, and Interface 210
9.2.2.1 Epoxy Resin 210
9.2.2.2 Reinforcing Fibers 214
9.2.2.3 Interface 216
9.2.3 Failure Envelopes of UD Composite Systems 218
9.2.4 In Situ Simulations 223
9.2.4.1 Tension 227
9.2.4.2 Compression 229
9.2.5 Longitudinal Failure 232
9.3 Meso-Models: Onset and Propagation of Ply Damage 239
9.3.1 Smeared Crack Model for Transverse Fracture 243
9.3.1.1 Initiation Criterion 243
9.3.1.2 Intersection with the Fracture Surface 245
9.3.1.3 Traction Tensor 248
9.3.1.4 Smeared Crack Model 251
9.3.2 Damage Model for Longitudinal Fracture 255
9.3.3 Preliminary Verification and Validation 263
9.4 Macro-Models: Finite Fracture Mechanics 270
9.5 Conclusions and Outlook 277
References 279
Part III 285
10 Microscale Characterization Techniques of Fibre-Reinforced Polymers 286
10.1 Virtual Testing for Structural Composite Materials: A Multiscale Perspective 286
10.2 Fibre Characterization 289
10.3 Matrix Characterization 292
10.3.1 Instrumented Nanoindentation 292
10.3.2 Micropillar Compression Tests 294
10.4 Fibre/Matrix Interface Characterization 297
10.5 Conclusions and Future Works 299
References 300
11 Fibre Distribution and the Process-Property Dilemma 303
11.1 Introduction 303
11.1.1 Process 303
11.1.2 Properties 305
11.1.3 Voids and Resin-Rich Volumes 305
11.1.4 Micro-/Meso-Structural Characterisation 307
11.2 Tessellation Techniques 307
11.3 Fractal Dimensions 309
11.3.1 Discontinuous Fibre Composites 311
11.3.2 Continuous Fibre Composites 311
11.4 Concluding Remarks 314
References 315
12 Analysis of Defect Developments in Composite Forming 320
12.1 Introduction 320
12.2 Analysis of Wrinkling of Composite Reinforcements During Forming 321
12.2.1 Unidirectional Materials 321
12.2.2 Explicit Approach for the Analysis of Wrinkling in Woven Reinforcement Forming 322
12.2.3 Shell Finite Element Made of Textile Reinforcement 323
12.2.4 Simulation of Wrinkle Development in Textile Reinforcement Forming 325
12.3 Mesoscopic Analyses: Slippage Between Yarns 328
12.3.1 Slippage During Reinforcement Forming 328
12.3.2 Mesoscopic FE Analyses 328
12.4 Transition Zones and Second-Gradient Approach 330
12.4.1 Transition Zone in Preforms 330
12.4.2 Second-Gradient Approach 332
12.4.3 Simulation of Transition Zones 332
12.4.4 S Shape in a Bias Extension Test on an Unbalanced Woven Reinforcement 333
12.5 Conclusions 333
References 335
Part IV 339
13 Deformation Mechanisms of Carbon Fibres and Carbon Fibre Composites 340
13.1 Introduction 340
13.2 Deformation of Carbon Fibres 341
13.2.1 Raman Spectra of Carbon Fibres 341
13.2.2 Stress-Induced Raman Band Shifts 343
13.3 Deformation of Carbon Fibres in Composites 347
13.3.1 Analysis of Micromechanics 347
13.3.2 Effect of Fibre Surface Treatment 348
13.3.3 Interfacial Shear Stress 354
13.4 Conclusions 355
References 355
14 Micromechanical Evidences on Interfibre Failure of Composites 357
14.1 Introduction 357
14.2 Tools 358
14.3 Micromechanics to Understand Interfibre Failure 360
14.4 Interfibre Failure 364
14.4.1 Under Tension 365
14.4.2 Under Compression 369
14.5 Micromechanics in Fatigue Loading 374
14.6 The Role of Residual Stresses 374
14.6.1 Under Tension 375
14.6.2 Under Compression 377
14.7 Other Studies 378
14.7.1 The Role of a Secondary Fibre 378
14.7.2 Scale Effect at Micromechanical Level 381
14.8 Conclusions 385
References 386
15 Progressive Damage in Fibre-Reinforced Composites: Towards More Accurate and Efficient Computational Modelling and Analysis 389
15.1 Introduction 389
15.2 Modelling Cracks and Delaminations 392
15.3 The Smeared Crack Method and Open-Hole Problems 394
15.3.1 Open-Hole Problems 394
15.3.2 Modelling of Open-Hole Problems 396
15.3.3 Model Predictions and Comparison with Experimental Results 401
15.4 Development of Novel Numerical Methods 405
15.4.1 The XFEM-CE Method 406
15.4.2 Floating Node Method 408
15.5 Conclusions 419
References 420
16 Predicting Properties of Undamaged and Damaged Carbon Fibre Reinforced Composites 422
16.1 Introduction 422
16.2 Prediction of Effective Thermo-Elastic Constants for Undamaged UD Composites 423
16.3 Effective Thermo-Elastic Constants for Plies of Undamaged UD Composites 428
16.3.1 Stress/Strain Relations for Individual Plies in a Laminate 428
16.3.2 Effective Stress/Strain Relations for any Undamaged Symmetric Laminate 432
16.4 Stress Transfer Mechanics for Fibre Fracture and Matrix Cracking (Perfect Interfaces) 436
16.5 Modelling Crack Bridging of Matrix Cracks for Perfectly Bonded Interfaces 439
16.6 Modelling Crack Bridging with Debonded Interfaces 444
16.7 Effects of Ply Cracking on Thermo-Elastic Constants of Damaged Laminates 452
16.7.1 Macroscopic Effective Stress/Strain Relations for a Laminate 453
16.7.2 Effective Thermo-Elastic Constants for Damaged Laminates 455
16.8 Predicting Progressive Ply Crack Formation in Multiple-Ply Laminates 456
16.9 Embedded Ply Cracks 459
16.10 Closing Remarks 461
References 462
Part V 465
17 Composites Toughen Up! 466
17.1 Introduction 466
17.2 Matrix Resins in the 1970s 466
17.2.1 Principles of Epoxy Toughening 467
17.3 `Second Generation' Epoxy Matrices, in the 1980s 468
17.4 The `Thermoplastics Versus Thermosets' Debate 470
17.5 Not Starting Cracks 471
17.5.1 Interleaf Toughening 472
17.6 Stopping Cracks 473
17.6.1 Microfasteners for Use with Prepregs 473
17.6.2 Microfasteners for Use with Dry Fibre Preforms and Liquid Resin Infusion Processes 475
17.7 Where in the Structure is the Toughness Needed? 476
17.8 Damage Tolerant Structures of the Future 479
References 480
18 Slow Cracking in Composite Materials: Catastrophic Fracture of Composite Structures 483
18.1 In Search of Structural Integrity: A Point of View 483
18.2 Contemporary Composites in Service 489
18.3 Why Carbon Fibre? 491
18.4 So Why Do Materials Still Crack and Structures Still Collapse? 493
18.5 The Traditional Route of Engineering Design 495
18.6 Fitness Considerations for Long-Life Implementation 497
18.7 Structural Integrity and Length Scale 498
18.8 Structural Integrity and Multi-scale Modelling 501
18.9 At the Heart of Structural Integrity 503
18.10 A Guide to Thinking and Planning a Physical Model 506
18.11 Constitutive Models: The Internal Material State Variable Method 507
18.12 Multi-scale Modelling and Computer Simulation 510
18.12.1 Simulation of a Delamination Crack Using a Cohesive Interface Model 514
18.13 The Future Looks Bright 515
18.14 Final Remarks 519
References 521
Further Reading 522
19 Finite Fracture Mechanics: A Useful Tool to Analyze Cracking Mechanisms in Composite Materials 523
19.1 Introduction 523
19.2 The Coupled Criterion 524
19.2.1 Full Field Formulation 525
19.2.2 Matched Asymptotic Expansions Formulation 528
19.3 Free-Edge Delamination in Laminated Composites 529
19.4 Crack Deflection at the Fiber/Matrix Interface 531
19.4.1 The Cook and Gordon Mechanism 532
19.4.2 A Matrix Crack Impinging Upon the Fiber/Matrix Interface 536
19.4.3 Influence of Mode Mix 538
19.5 Conclusion 538
References 539
20 Traction-Separation Relations in Delamination of Layered Carbon-Epoxy Composites Under Monotonic Loads: Experiments and Modeling 543
Nomenclature 543
20.1 Introduction 544
20.2 Fiber Bridging in Delamination and Fracture 546
20.3 Internal Strain Measurements Using Fiber Bragg Grating Sensors 548
20.4 Experimental Methods 550
20.4.1 Material and Specimen Preparation 550
20.4.2 Fracture Tests 553
20.4.3 Numerical Analysis 554
20.5 Iterative Approach to Identify Bridging Tractions 555
20.6 Cohesive Zone Modeling 558
20.7 Results 559
20.7.1 Intralaminar Crack in Uniaxial Carbon Epoxy 559
20.7.2 Interlaminar Crack in Uniaxial Carbon Epoxy 565
20.7.3 Delamination in Cross Ply Carbon-Epoxy Specimen 569
20.8 Micromechanics Approach Using Embedded-Cell Model 576
20.9 Conclusions 580
References 581
21 Damage and Failure Analysis of Bolted Joints in Composite Laminates 585
21.1 Introduction 585
21.2 Critical Stresses and Failure Modes 587
21.3 Stress Analysis 589
21.3.1 Analytical Methods 589
21.3.2 Experimental Methods 590
21.3.3 Numerical Methods 591
21.4 Strength Prediction Techniques 593
21.4.1 Strength Prediction Based on Hole Boundary Stresses 594
21.4.2 Semiempirical Techniques 595
21.4.3 Progressive Failure Analysis (PFA) 596
21.4.4 The Damage Zone Model (DZM) 598
21.5 Measurement of Joint Strength and Determination of Subcritical Damage Locations 599
21.5.1 Material System and Specimen Design 599
21.5.2 Measurement of Joint Strength and Determination of Damage Locations 600
21.5.2.1 Cross-Ply Specimens 600
21.5.2.2 Quasi-Isotropic Specimens 606
21.6 Strength Prediction Based on Subcritical Damage Modelling 612
21.6.1 Validation of Subcritical Damage Predictions 612
21.6.2 Finite Element Modelling Including Subcritical Damage Planes 616
21.6.3 Strength Prediction in Cross-Ply Laminates 624
21.6.4 Strength Prediction in Quasi-Isotropic Laminates 628
21.7 Conclusions 631
References 634
22 Interfaces, Cracks and Toughness: City Cars Made from Composites 639
22.1 Introduction to City Cars 639
22.2 Composites, Interfaces, Cracks and Toughness 641
22.3 Mechanics of Crack Stopping and Deflection at Interfaces 644
22.4 Composite Components in Motor Sport 647
22.5 New Drivetrains: The Composite Lean Weight Hydrogen Fuel Cell City Car, Microcab 649
22.6 Composite Construction 652
22.7 Future Possibilities for Composites in City Car Applications 654
22.8 Conclusions 656
References 656
Part VI 658
23 A Virtual Testing Approach for Laminated Composites Based on Micromechanics 659
23.1 Introduction 659
23.2 The Reference Virtual Material 661
23.2.1 The Main Damage Mechanisms 661
23.2.2 The RVM as a Computational Hybrid Micromechanics Model 662
23.2.2.1 Basic Aspects 662
23.2.2.2 Modeling of the Fiber-Matrix Material 663
23.2.2.3 Modeling of Delamination and Microcracking 666
23.2.2.4 Fiber Breaking 668
23.2.2.5 Structure Computation 668
23.2.3 Toward a Unified Model 669
23.2.4 Extension 669
23.3 The Micro-Meso Bridge 670
23.3.1 The Method 670
23.3.2 The Tools 672
23.3.2.1 The Ply Basic Problem 672
23.3.2.2 The Interface Basic Problem 675
23.4 The Damage Mesomodel 677
23.4.1 The Single Layer 678
23.4.1.1 Diffuse Damage, Microcracking, and Inelasticity 678
23.4.1.2 Fiber Breaking 679
23.4.2 The Interface 679
23.5 Structure Computation 680
23.5.1 Localization Limiters and Numerical Parameters 680
23.5.2 Split Detection and Propagation 681
23.5.3 Applications 684
23.5.4 Limits 685
23.6 Conclusion 685
Appendix: The Basic Damage Law 686
References 687
24 Virtual Testing of Composite Structures: Progress and Challenges in Predicting Damage, Residual Strength and Crashworthiness 691
Nomenclature 691
24.1 Introduction 692
24.2 Computational Strategy 694
24.2.1 Interlaminar Damage Model 695
24.2.2 Intralaminar Damage Model 696
24.2.2.1 Fibre-Dominated Failure Modes 697
24.2.2.2 Non-linear Shear Behaviour 699
24.2.2.3 Matrix-Dominated Failure Modes 701
24.2.3 Implementation of Damage Model 708
24.2.3.1 ABAQUS VUMAT Subroutine 708
24.2.3.2 Element Deletion Strategy 708
24.3 Material Characterisation 708
24.3.1 Interlaminar Fracture Toughness 708
24.3.2 Intralaminar Fracture Toughness 713
24.3.3 Non-linear Shear Behaviour 714
24.4 Predicting Impact Damage and CAI 716
24.4.1 Finite Element Model 716
24.4.2 Results 718
24.5 Modelling Composite Crushing 721
24.5.1 Crashworthiness Assessment 721
24.5.2 Crushing of Thermoset Composite Wedge Specimens 721
24.5.3 Crushing of Corrugated Thermoplastic Composite Specimens 722
24.5.3.1 Experimental Testing 722
24.5.3.2 Crushing Damage Mechanisms 725
24.5.3.3 Finite Element Model 725
24.5.3.4 Results and Discussion 727
24.6 Concluding Remarks 732
References 733
25 Contribution of Virtual Simulation to Industrialisation of Carbon Fibre-Reinforced Polymer (CFRP) Composites for Manufacturing Processes and Mechanical Performance 736
25.1 Introduction 736
25.2 Manufacturing Methods and Process Simulation 738
25.3 FE Analysis Methods 738
25.4 Fabric Draping 739
25.5 Fabric Draping: Geometric Methods 740
25.6 Thermoforming Simulation 741
25.7 Fabric Draping: FE Simulation 743
25.8 Chaining Draping of Draping Results 744
25.9 Mesoscopic Fabric Drape Modelling 745
25.10 Braiding 746
25.11 Infusion Analysis 749
25.12 Failure, Impact and Crash 751
25.13 Conclusions 752
References 753
Part VII 755
26 Multi-scale Progressive Failure Modeling: From Nano-structured Carbon Fibers to Textile Composites 756
26.1 Introduction 756
26.2 Generation of 3-D Mosaic Chain Models 758
26.3 General Discretization Approach of Composite Structure 759
26.4 General 3-D Mosaic Model and Analysis Approach 761
26.5 Progressive Failure Modeling of 3-D Mosaic Chains 763
26.6 Nanoscale Progressive Failure Modeling of Carbon Fibers 764
26.7 Microscale Progressive Failure Modeling of Unidirectional Composites 768
26.8 Mesoscale Progressive Failure Modeling of Plain Weave Composites 775
26.9 Mesoscale Progressive Failure Modeling of Non-crimp 3-D Weave Composites 778
26.10 Conclusions 780
References 781
27 Textile Structural Composites: From 3-D to 1-D Fiber Architecture 783
27.1 Introduction 783
27.1.1 Aerospace Textile Structural Composites 784
27.1.2 Aircraft Textile Structural Composites 786
27.1.3 Automotive Textile Structural Composites 787
27.2 Integrated Design for Manufacturing of Textile Composites 789
27.2.1 Classification of Textile Preforms 792
27.2.2 Engineering Parameters of Textile Preforms 793
27.2.3 The Role of Fiber Architecture in Composite 796
27.2.3.1 Formability 797
27.2.3.2 Permeability 798
27.2.3.3 Properties 798
27.2.4 Engineering Design of Textile Composites 799
27.2.4.1 3-D Braided Structure Analysis 801
27.2.4.2 The Fabric Geometry Model 805
27.2.4.3 Application of the FGM 807
27.3 New Frontiers 810
27.3.1 Low-Cost Carbon Fiber from Renewable Resources 812
27.3.2 Strong Carbon–Carbon Composite Nanofiber 816
27.3.3 Smart Composite Nanofiber 819
27.3.3.1 Ultrasensitive Strain Sensor 820
27.3.3.2 Piezoelectric Nanowire-Based Force Sensor 824
27.3.4 Carbon Nanofiber Yarn Assembly 825
27.3.5 New Preforming Technology: Hexagonal 3-D Braiding 827
27.4 Summary and Conclusions 831
References 832
28 Experimental and Multiscale Numerical Studies of Woven Fabric Carbon Composite Cylinder Subjected to Internal Pressure Loading 836
28.1 Introduction 836
28.2 Fabrication of Composite Cylinders 839
28.3 Multiscale Analysis Technique 841
28.4 Experimental Device 847
28.5 Results and Discussion 850
28.6 Conclusions 854
References 855
Part VIII 857
29 Fatigue of 2D and 3D Carbon-Fiber-Reinforced Polymer Matrix Composites and of a Unitized Polymer/Ceramic Matrix Composite at Elevated Temperature 858
29.1 Introduction 858
29.2 Experimental Arrangements 860
29.2.1 Experimental Materials 860
29.2.2 Mechanical Testing 862
29.3 Mechanical Behavior 864
29.3.1 Tensile Stress–Strain Behavior: Effect of Elevated Temperature 864
29.3.2 Tension–Tension Fatigue at Elevated Temperature 869
29.4 Composite Failure: Examination with Optical Microscopy 884
29.5 Concluding Remarks 887
References 890
30 Carbon Fibers in Tribo-composites 893
Abbreviations 893
30.1 Introduction 894
30.2 Survey on Sliding Wear of Carbon Fiber/Polymer Composites 896
30.2.1 Typical Filler and Matrix Materials 896
30.2.2 Carbon Versus Glass Fiber Reinforcements 899
30.2.3 High-Modulus Versus High-Strength Carbon Fibers 904
30.2.4 Influence of Fiber Orientation 907
30.2.5 Abrasion Due to Counterface Roughness 912
30.2.6 Kinds of Counterface Material 915
30.2.7 Environmental Effects 917
30.3 Tribo-composites Containing Carbon Fibers in Combination with Nanofillers 927
30.3.1 Addition of Ceramic Nanoparticles 927
30.3.2 Artificial Neural Network Approach 931
30.3.3 Multifunctionality by Addition of Carbon Nanotubes 936
30.4 Carbon Fibers Composites for Special Tribo-applications 938
30.4.1 High-Friction Materials 938
30.4.2 Friction and Wear of Carbon Fiber/Glass Composites 940
30.4.3 Friction and Wear of Carbon Fiber/Metal Composites 943
30.5 Concluding Remarks 945
References 946
Erratum 954