Gdoutos Major Accomplishments in Composite Materials and Sandwich Structures

An Anthology of ONR Sponsored Research
1. Auflage 2009
ISBN: 978-90-481-3141-9
Verlag: Springer-Verlag
Format: PDF
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 818 Seiten

Autoren/Hrsg.

Gdoutos, E.E.

Inhaltsverzeichnis

1;Preface;5
2;Contents;11
3;Contributors;15
4;Chapter 1;19
4.1;Accelerated Testing for Long-Term Durability of Various FRP Laminates for Marine Use;19
4.1.1;1 Introduction;20
4.1.2;2 Accelerated Testing Methodology;20
4.1.2.1;2.1 Procedure of ATM;20
4.1.2.2;2.2 Applicability of ATM;22
4.1.2.3;2.3 Theoretical Verification of TTSP;22
4.1.3;3 Experimental Procedures;25
4.1.3.1;3.1 Preparation of Specimens;25
4.1.3.2;3.2 Tests;26
4.1.4;4 Results and Discussion;29
4.1.4.1;4.1 Creep Compliance;29
4.1.4.2;4.2 Flexural CSR Strength;30
4.1.4.3;4.3 Flexural Fatigue Strength;33
4.1.5;5 Conclusions;39
4.1.6;Navy Relevance;39
4.1.7;References;40
5;Chapter 2;42
5.1;Carbon Fiber–Vinyl Ester Interfacial Adhesion Improvement by the Use of an Epoxy Coating;42
5.1.1;1 Introduction;42
5.1.2;2 Materials and Methods;43
5.1.2.1;2.1 Materials;43
5.1.2.2;2.2 Methods;44
5.1.2.2.1;2.2.1 Microindentation Test;44
5.1.2.2.2;2.2.2 Thermogravimetric Analysis (TGA);45
5.1.2.2.3;2.2.3 Dynamic Mechanical Thermal Analysis (DMTA);45
5.1.2.2.4;2.2.4 Environmental Scanning Electron Microscopy (ESEM);45
5.1.3;3 Preferential Adsorption of Some Constituents of the Matrix on the Carbon Fiber Surface and Its Influence on Interfacial Adhesion;46
5.1.3.1;3.1 Evidence of Preferential Adsorption of Some Constituents of the Matrix on the Carbon Fiber Surface;46
5.1.3.2;3.2 Influence on Interfacial Adhesion;46
5.1.3.2.1;3.2.1 Influence of the Concentration of the Initiator;47
5.1.3.2.2;3.2.2 Influence of the Concentration of the Promoter;48
5.1.3.2.3;3.2.3 Influence of the Concentration of the Accelerator;49
5.1.4;4 Influence of Cure Volume Shrinkage on Interfacial Adhesion;50
5.1.5;5 Improvement of Interfacial Adhesion by the Use of an Epoxy Coating;52
5.1.5.1;5.1 Optimization of the Coating Process;52
5.1.5.2;5.2 Interactions Between the Epoxy Coating and the Components of the Vinyl Ester Matrix;53
5.1.5.2.1;5.2.1 Influence of the Concentration of the Initiator;54
5.1.5.2.2;5.2.2 Influence of the Concentration of the Promoter;55
5.1.5.2.3;5.2.3 Influence of the Concentration of the Accelerator;55
5.1.5.2.4;5.2.4 Influence of Monomers;56
5.1.5.3;5.3 Influence of the Cure Volume Shrinkage with the Use of an Epoxy Coating;57
5.1.5.4;5.4 Qualitative Assessment of the Use of an Epoxy Coating on the Mechanical Properties of a Carbon Fiber–Vinyl Ester Composite Cured at High Temperature;58
5.1.5.5;5.5 Determination of the Optimal Thickness of the Coating by a Finite Element Analysis;60
5.1.5.6;5.6 Determination of the Thickness of the Interdiffusion Zone by a Nanoindentation Scratch Test;62
5.1.6;6 Conclusion;63
5.1.7;References;64
6;Chapter 3;66
6.1;A Physically Based Cumulative Damage Formalism;66
6.1.1;1 Introduction;66
6.1.2;2 Kinetic Crack Based Cumulative Damage and Life Prediction;68
6.1.3;3 A Special Form;72
6.1.4;4 Cyclic Fatigue;74
6.1.5;5 Probabilistic Generalization;76
6.1.6;6 Examples;77
6.1.7;7 Extended Life Examples;78
6.1.8;8 Conclusions;79
6.1.9;References;80
7;Chapter 4;81
7.1;Delamination of Composite Cylinders;81
7.1.1;1 Introduction;81
7.1.2;2 Materials and Specimens;82
7.1.3;3 Delamination Fracture Testing;85
7.1.4;4 Impact Testing of Cylinders;86
7.1.5;5 External Pressure Tests of Cylinders;86
7.1.6;6 Results and Discussion;89
7.1.6.1;6.1 Delamination Fracture Test Results;89
7.1.6.2;6.2 Influence of Impact;90
7.1.6.3;6.3 External Pressure Test Results;90
7.1.7;7 Conclusions;98
7.1.8;References;98
8;Chapter 5;100
8.1;Modeling of Progressive Damage in High Strain–Rate Deformations of Fiber-Reinforced Composites;100
8.1.1;1 Introduction;100
8.1.2;2 Progressive Damage Model;101
8.1.3;3 Implementation of the Damage Model;105
8.1.3.1;3.1 Brief Description of the Numerical Technique;105
8.1.3.2;3.2 Simulation of Material Failure;106
8.1.3.3;3.3 Energy Dissipation;106
8.1.3.4;3.4 Verification of the Code;107
8.1.3.5;3.5 Validation of the Mathematical Model;108
8.1.4;4 Parametric Studies on a Typical Laminated Composite;110
8.1.4.1;4.1 Effect of Mesh Size;111
8.1.4.2;4.2 Lay-Up Sequence;113
8.1.4.3;4.3 Target Thickness;115
8.1.4.4;4.4 Fiber Orientation;115
8.1.4.5;4.5 Delamination;118
8.1.4.6;4.6 Figure of Merit;118
8.1.4.7;4.7 Remarks;119
8.1.4.8;4.8 Limitations of the Model;119
8.1.5;5 Conclusions;120
8.1.6;References;121
9;Chapter 6;123
9.1;Post-Impact Fatigue Behavior ofWoven and Knitted Fabric CFRP Laminates for Marine Use;123
9.1.1;1 Introduction;123
9.1.2;2 Materials and Testing Methods;124
9.1.2.1;2.1 Materials and Molding Method;124
9.1.2.2;2.2 Specimens and Impact Test;125
9.1.2.3;2.3 Compression After Impact (CAI) Test and Post-Impact Fatigue (PIF) Test;126
9.1.2.4;2.4 Water Absorption Condition;127
9.1.3;3 Approach to Evaluate Damages;127
9.1.4;4 Impact Damage of CFRP Laminates;129
9.1.4.1;4.1 Plain Woven CFRP Laminate;129
9.1.4.2;4.2 Multi-axial Knitted CFRP Laminate;130
9.1.4.3;4.3 Three-Dimensional Characterization of Impact Damage Within CFRP Laminates;132
9.1.5;5 Compressive Strength and Fatigue Strength of Impact Damaged CFRP Laminates;133
9.1.5.1;5.1 Effect of Water Absorption on Post-Impact Fatigue Properties;133
9.1.5.2;5.2 Damage Evolution Mechanism in Plain Woven CFRP Laminates;134
9.1.5.3;5.3 Damage Evolution Mechanism in Multi-axial Knitted CFRP Laminates;138
9.1.6;5 Conclusions;140
9.1.7;References;141
10;Chapter 7;143
10.1;Dynamic Interaction of Multiple Damage Mechanisms in Composite Structures;143
10.1.1;1 Introduction;143
10.1.2;2 Modeling Multiple Delamination Fracture in Laminated and Multilayered Systems;145
10.1.2.1;2.1 Theoretical Approach;145
10.1.2.2;2.2 Energy Release Rate and Stress Intensity Factors in Homogeneous Orthotropic Beams;146
10.1.3;3 Interaction Effects of Multiple Delaminations on Fracture Parameters;149
10.1.3.1;3.1 Amplification and Shielding of the Energy Release Rate;149
10.1.3.2;3.2 Interaction Effects on Mode Ratio;151
10.1.3.3;3.3 Coupling of Interaction and Dynamic Effects;153
10.1.3.3.1;3.3.1 Dynamic Response of Beams with Single Stationary Delaminations;153
10.1.3.3.2;3.3.2 Dynamic Response of Beams with Multiple Stationary Delaminations;155
10.1.4;4 Interaction Effects of Multiple Delaminations on Crack Growth Characteristics and Macrostructural Behaviour;158
10.1.4.1;4.1 Local Instabilities and Strengthening Mechanisms;158
10.1.4.2;4.2 Stability of the Equality of Length of Systems of Equal Length Delaminations;159
10.1.4.2.1;4.2.1 Equally Spaced and Equal Length Cracks in Homogeneous Beams (Static Loading);160
10.1.4.2.2;4.2.2 Equal Length and Unequally Spaced Cracks in Homogeneous Beams (Static Loading);160
10.1.4.2.3;4.2.3 Dynamic Loading Conditions;161
10.1.4.2.3.1;Equally Spaced and Equal Length Cracks in Homogeneous Beams;161
10.1.4.2.3.2;Delamination Configurations Falling into the Stable Quasi-static Domain;162
10.1.4.2.3.3;Delamination Configurations Falling into the Unstable Quasi-static Domain;164
10.1.4.3;4.3 Crack Growth Characteristics in Systems of Unequal Length Cracks;165
10.1.5;5 Improving Mechanical Performance Through Controlled Delamination Fracture;166
10.1.5.1;5.1 Energy Absorption Through Multiple Delamination Fracture;166
10.1.5.2;5.2 Damage and Impact Tolerance;169
10.1.6;6 Indentation Response of Composite Sandwich Beams in the Presence of Skin Damage;171
10.1.6.1;6.1 Continuously Supported Sandwich Beam (F = 0);172
10.1.6.2;6.2 Sandwich Beam with End Restraints (F Not Equal 0);173
10.1.6.3;6.3 Characteristic Lengths;174
10.1.7;7 Conclusions;175
10.1.8;References;176
11;Chapter 8;179
11.1;A Review of Research on Impulsive Loading of Marine Composites;179
11.1.1;1 Introduction;179
11.1.2;2 Outline;180
11.1.3;3 Experimental Studies;181
11.1.3.1;3.1 Underwater Tests;181
11.1.3.1.1;3.1.1 Test Procedures and Instrumentations;181
11.1.3.1.2;3.1.2 Response of Marine Structural Materials to Underwater Blast Loading;183
11.1.3.2;3.2 In-Air Tests;185
11.1.3.2.1;3.2.1 Test Procedures and Instrumentations;185
11.1.3.2.2;3.2.2 Response of Marine Structural Materials to In-Air Shock and Blast Loading;187
11.1.4;4 Theoretical and Computational Studies;191
11.1.4.1;4.1 Analysis of Marine Panels;191
11.1.4.1.1;4.1.1 Panel Response to Free Field Blast Loading;191
11.1.4.1.2;4.1.2 Fluid–Structure Interaction in Sandwich Composites;194
11.1.4.2;4.2 Analysis of Full-Scale Marine Structures;196
11.1.5;5 Closing Remarks;198
11.1.6;References;201
12;Chapter 9;205
12.1;Failure Modes of Composite Sandwich Beams;205
12.1.1;1 Introduction;206
12.1.2;2 Sandwich Materials Investigated;207
12.1.2.1;2.1 Facesheet Materials;207
12.1.2.2;2.2 Core Materials;207
12.1.3;3 Facesheet Failure;214
12.1.4;4 Facesheet Debonding;217
12.1.5;5 Core Failures;221
12.1.6;6 Indentation Failure;224
12.1.7;7 Facesheet Wrinkling Failure;228
12.1.8;8 Failure Mode Interaction;230
12.1.9;9 Conclusions;232
12.1.10;References;233
13;Chapter 10;236
13.1;Localised Effects in Sandwich Structures with Internal Core Junctions: Modelling and Experimental Characterisation of Load Response, Failure and Fatigue;236
13.1.1;1 Introduction;236
13.1.2;2 Prediction of Failure in Sandwich Structures with Core Junctions;238
13.1.2.1;2.1 Failure Criteria for Sandwich Core Materials;238
13.1.3;3 Core Junctions in Sandwich Panels Subjected to In-Plane Loading;242
13.1.3.1;3.1 Test Specimens;242
13.1.3.2;3.2 Material Properties;244
13.1.3.3;3.3 Experimental Investigation – Part 1: Quasi-static Tests;248
13.1.3.4;3.4 Finite Element Analyses (FEA);252
13.1.3.5;3.5 Experimental Investigation – Part 2: Fatigue Tests;259
13.1.3.6;3.6 Discussion and Conclusions (In-Plane Loading);261
13.1.4;4 Core Junctions in Sandwich Panels Subjected to Transverse Shear Loading;262
13.1.4.1;4.1 Sandwich Test Specimens;262
13.1.4.2;4.2 Experimental Results – Part 1: Quasi-static Tests;263
13.1.4.3;4.3 Finite Element Analyses (FEA);269
13.1.4.4;4.4 Experimental Results – Part 2: Fatigue Tests;277
13.1.4.5;4.5 Discussion and Conclusions (Transverse Shear Loading);282
13.1.5;5 Summary and Conclusions;282
13.1.6;References;283
14;Chapter 11;285
14.1;Damage Tolerance of Naval Sandwich Panels;285
14.1.1;1 Introduction and Background;285
14.1.2;2 Fracture of Foam Core Materials;287
14.1.3;3 Disbonds in Sandwich Beams;288
14.1.4;4 Impact Damage in Sandwich Beams;291
14.1.5;5 Interface Disbonds in Sandwich Panels;293
14.1.6;6 Impact Damage in Sandwich Panels;297
14.1.7;7 Damage Tolerance Scheme for Naval Sandwich Structures;302
14.1.8;References;307
15;Chapter 12;310
15.1;Size Effect on Fracture of Composite and Sandwich Structures;310
15.1.1;1 Introduction;310
15.1.2;2 Size Effect on the Tensile Strength of Notched Fiber–Composite Laminates [23];313
15.1.2.1;2.1 Introduction;313
15.1.2.2;2.2 Experimental;314
15.1.2.3;2.3 Size Effect;315
15.1.2.4;2.4 Conclusions;317
15.1.3;3 Size Effect on the Flexural Strength of Fiber–Composite Laminates [34];318
15.1.3.1;3.1 Introduction;318
15.1.3.2;3.2 Size Effect;318
15.1.3.3;3.3 Experimental Studies;320
15.1.3.4;3.4 Conclusions;321
15.1.4;4 Size Effect on the Compression Strength of Fiber–Composite Laminates [42];321
15.1.4.1;4.1 Introduction;321
15.1.4.2;4.2 Experimental;322
15.1.4.3;4.3 Conclusions;325
15.1.5;5 Size Effect on Fracture of Polymeric Foams [45];325
15.1.5.1;5.1 Introduction;325
15.1.5.2;5.2 Experimental;326
15.1.5.3;5.3 Size Effect;327
15.1.5.4;5.4 Conclusions;331
15.1.6;6 Size Effect on Compressive Strength of Sandwich Panels [54];332
15.1.6.1;6.1 Introduction;332
15.1.6.2;6.2 Experimental;332
15.1.6.3;6.3 Size Effect;334
15.1.6.4;6.4 Conclusions;336
15.1.7;7 Size Effect of Cohesive Delamination Fracture Triggered by Sandwich Skin Wrinkling [55];337
15.1.7.1;7.1 Introduction;337
15.1.7.2;7.2 Size Effect;337
15.1.7.3;7.3 Conclusions;341
15.1.8;References;341
16;Chapter 13;344
16.1;Elasticity Solutions for the Buckling of Thick Composite and Sandwich Cylindrical Shells Under External Pressure;344
16.1.1;1 Introduction;344
16.1.2;2 Formulation;346
16.1.3;3 Pre-buckling State;352
16.1.4;4 Perturbed State;357
16.1.5;5 Solution of the Eigen-Boundary-Value Problem for Differential Equations;359
16.1.6;6 Results and Discussion;361
16.1.7;References;367
17;Chapter 14;369
17.1;An Improved Methodology for Measuring the Interfacial Toughness of Sandwich Beams;369
17.1.1;1 Introduction;369
17.1.2;2 Test Methods Considered;370
17.1.3;3 Geometries Considered;371
17.1.4;4 Finite Element Modeling;372
17.1.5;5 MCSB Evaluation;374
17.1.6;6 Preliminary Evaluation of the TSD Test;375
17.1.7;7 Data Reduction in the MP Test;376
17.1.8;8 TSD and MP Experiments;380
17.1.9;9 Mechanical Attachments;382
17.1.10;10 Conclusions;383
17.1.11;References;383
18;Chapter 15;385
18.1;Structural Performance of Eco-Core Sandwich Panels;385
18.1.1;1 Introduction;386
18.1.2;2 Design of Test Specimens;386
18.1.2.1;2.1 Short Beam Shear Test Specimen;387
18.1.2.2;2.2 Four-Point Flexure Test Specimen;388
18.1.2.3;2.3 Edgewise Compression Test Specimen;390
18.1.3;3 Fabrication of Sandwich Panel and Specimen;394
18.1.4;4 Tests;395
18.1.4.1;4.1 Short Beam Shear Test;396
18.1.4.2;4.2 Four-Point Flexure Test;396
18.1.4.3;4.3 Edgewise Compression Test;397
18.1.5;5 Test Results and Discussion;399
18.1.5.1;5.1 Short Beam Shear Test;399
18.1.5.2;5.2 Four-Point Flexure Test;400
18.1.5.3;5.3 Edgewise Compression Test;405
18.1.6;6 Concluding Remarks;409
18.1.7;References;410
19;Chapter 16;411
19.1;The Use of Neural Networks to Detect Damage in Sandwich Composites;411
19.1.1;1 Introduction;411
19.1.2;2 Nondestructive Evaluation;412
19.1.2.1;2.1 Thermography Based NDE;413
19.1.2.1.1;2.1.1 Modeling;414
19.1.2.1.2;2.1.2 Validation;415
19.1.2.1.3;2.1.3 Test Cases and Results;416
19.1.2.2;2.2 Vibrations Based NDE;417
19.1.2.2.1;2.2.1 Modeling;418
19.1.2.2.2;2.2.2 Validation;420
19.1.2.2.3;2.2.3 Test Cases and Results;421
19.1.2.3;3 Artificial intelligence (AI) in Damage Detection;422
19.1.2.3.1;3.1 Neural Network Based Damage Detection;423
19.1.2.3.1.1;3.1.1 Thermographic Based NN Implementation;424
19.1.2.3.1.2;3.1.2 Curvature Based NN Implementation;426
19.1.2.3.1.3;3.1.3 Multi-component NN Implementation;426
19.1.2.3.2;3.2 Testing and Evaluation;428
19.1.2.4;4 Conclusions;431
19.1.2.5;References;432
20;Chapter 17;434
20.1;On the Mechanical Behavior of Advanced Composite Material Structures;434
20.1.1;1 Introduction;435
20.1.2;2 High Strain Rate Effects on Composite Material Properties;435
20.1.3;3 Composite Sandwich Structures;438
20.1.4;References;442
21;Chapter 18;443
21.1;Application of Acoustic Emission Technology to the Characterization and Damage Monitoring of Advanced Composites;443
21.1.1;1 Background;443
21.1.2;2 Sample Acoustic Emission Applications;445
21.1.2.1;2.1 Edgewise Compression Tests of Polycore Sandwich Material;445
21.1.2.1.1;2.1.1 Background;445
21.1.2.1.2;2.1.2 Testing;446
21.1.2.1.3;2.1.3 Discussion of Results;446
21.1.2.1.4;2.1.4 Concluding Remarks;451
21.1.2.2;2.2 Isogrid Construction;451
21.1.2.2.1;2.2.1 Background;451
21.1.2.2.2;2.2.2 Testing;452
21.1.2.2.3;2.2.3 Discussion of Results;453
21.1.2.2.4;2.2.4 Concluding Remarks;457
21.1.2.3;2.3 Flexural Fatigue of Foam-Cored Composite Sandwich;458
21.1.2.3.1;2.3.1 Background;458
21.1.2.3.2;2.3.2 Testing;458
21.1.2.3.3;2.3.3 Results and Discussion;458
21.1.2.3.4;2.3.4 Concluding Remarks;461
21.1.3;3 Conclusion;462
21.1.4;References;462
22;Chapter 19;465
22.1;Ballistic Impacts on Composite and Sandwich Structures;465
22.1.1;1 Introduction;465
22.1.2;2 Models Based on Assumptions Regarding the Penetration Resistance;466
22.1.2.1;2.1 Constant Penetration Resistance;468
22.1.2.2;2.2 Assumption 2: Kinetic Energy Absorbed by Ejecta;470
22.1.2.3;2.3 Poncelet’s Assumption;474
22.1.2.4;2.4 Penetration Force Increases Linearly with the Velocity;475
22.1.2.5;2.5 Penetration Force Varies with v and v2;476
22.1.2.6;2.6 Summary;476
22.1.3;3 Projectile-Target Interaction Models;477
22.1.3.1;3.1 Normal Pressure on the Surface of the Projectile;477
22.1.3.2;3.2 Blunt-Ended Projectile;478
22.1.3.3;3.3 Conical-Tipped Projectile;478
22.1.3.4;3.4 Spherical Tipped Projectile;480
22.1.3.5;3.5 Effect of Friction;482
22.1.4;4 Factors Affecting the Ballistic Limit;482
22.1.4.1;4.1 Effect of Laminate Thickness and Projectile Diameter;483
22.1.4.2;4.2 Effect of Stacking Sequence;485
22.1.4.3;4.3 Effect of Obliquity;486
22.1.4.4;4.4 Effect of Projectile Density;487
22.1.5;5 Models Based on Static Test Results;488
22.1.6;6 Energy – Balance Models;490
22.1.7;7 Numerical Models;493
22.1.8;8 Impact on Sandwich Structures;494
22.1.9;9 Conclusions;496
22.1.10;References;496
23;Chapter 20;502
23.1;Performance of Novel Composites and Sandwich Structures Under Blast Loading;502
23.1.1;1 Introduction;503
23.1.2;2 Material Systems;505
23.1.2.1;2.1 Laminated Composites;505
23.1.2.1.1;2.1.1 E-Glass Vinyl Ester Composite (EVE);505
23.1.2.1.2;2.1.2 Carbon Fiber Vinyl Ester Composite (CVE);506
23.1.2.2;2.2 Layered Composites;506
23.1.2.2.1;2.2.1 Polyurea Layered Materials;506
23.1.2.3;2.3 Sandwich Composites;506
23.1.2.3.1;2.3.1 Polyurea Sandwich Composites;506
23.1.2.3.2;2.3.2 Sandwich Composites with 3D Woven Skin;506
23.1.2.3.3;2.3.3 Core Reinforced Sandwich Composites;507
23.1.2.3.4;2.3.4 Sandwich Composite with a Stepwise Graded Core;508
23.1.2.3.5;2.3.5 Pre-damaged Sandwich Composite;509
23.1.3;3 Experimental Setup;509
23.1.3.1;3.1 Shock Tube;509
23.1.3.2;3.2 Loading and Boundary Conditions;510
23.1.3.3;3.3 Pre-damage Procedure;511
23.1.3.4;3.4 High Speed Imaging;512
23.1.3.5;3.5 Blast Energy Calculation Procedure;513
23.1.4;4 Results and Discussion;513
23.1.4.1;4.1 Blast Resistance of Laminated Composites;513
23.1.4.2;4.2 Blast Resistance of Layered Composites;516
23.1.4.2.1;4.2.1 PU/EVE Layered Material;517
23.1.4.2.2;4.2.2 EVE/PU Layered Material;518
23.1.4.3;4.3 Blast Resistance of Sandwich Composites;519
23.1.4.3.1;4.3.1 Polyurea Based Sandwich Composites;519
23.1.4.3.2;4.3.2 Sandwich Composites with 3D Skin and Polymer Foam Core;522
23.1.4.3.3;4.3.3 Sandwich Composite with E-Glass Fiber and Polymer Foam Core;528
23.1.4.3.4;4.3.4 Sandwich Composites with Stepwise Graded Foam Cores;528
23.1.4.3.5;4.3.5 Pre-damaged Sandwich Composites;534
23.1.5;5 Summary;537
23.1.6;References;538
24;Chapter 21;540
24.1;Single and Multisite Impact Response of S2-Glass/ Epoxy Balsa Wood Core Sandwich Composites;540
24.1.1;1 Introduction;540
24.1.2;2 Experimental;541
24.1.2.1;2.1 Specimen Fabrication;541
24.1.2.2;2.2 High Velocity Impact Set Up;542
24.1.3;3 Model Description;542
24.1.3.1;3.1 Mesh Generation and Contact Definition;542
24.1.3.2;3.2 Composite Progressive Failure Model and Strain Softening Characteristics;544
24.1.3.2.1;3.2.1 Wood Material Model;544
24.1.4;4 Results and Discussion;546
24.1.4.1;4.1 Single Site Projectile Impact;546
24.1.4.1.1;4.1.1 Single Project Impact: Balsa Wood Core Only;546
24.1.4.1.1.1;Experiment;546
24.1.4.1.1.2;Simulation;547
24.1.4.1.2;4.1.2 Single Projectile Impact: Sandwich Composite;548
24.1.4.2;4.2 Simultaneous 0.30 and 0.50 Caliber Three Projectile Impact on the Sandwich Specimens;555
24.1.4.3;4.3 Delamination Factor, Sd for Multisite Impact Prediction;561
24.1.4.4;4.4 Fiber and Wood Damage;564
24.1.5;5 Summary and Conclusions;565
24.1.6;References;566
25;Chapter 22;569
25.1;Real-Time Experimental Investigation on Dynamic Failure of Sandwich Structures and Layered Materials;569
25.1.1;1 Introduction;569
25.1.2;2 Experimental Procedure;573
25.1.2.1;2.1 Materials and Specimens;573
25.1.2.2;2.2 Experimental Setup;575
25.1.3;3 Results and Discussion;576
25.1.3.1;3.1 Failure Process of Short Model Sandwich Specimens with Equal Layer Widths;576
25.1.3.2;3.2 Failure Process in Long Model Sandwich Specimens;578
25.1.3.3;3.3 Effect of Impact Speeds;582
25.1.3.4;3.4 Dynamic Failure Mode Transition;583
25.1.3.5;3.5 Dynamic Interface Debonding Ahead of a Main Incident Crack;585
25.1.3.6;3.6 New Progress on Dynamic Crack Branching;588
25.1.3.6.1;3.6.1 Special Experiments for Dynamic Crack Kinking and Branching;588
25.1.3.6.2;3.6.2 Dynamic Crack Branching and Kinking from aWeak Interface;588
25.1.3.6.3;3.6.3 Dynamic Crack Branching Initiated from a Notch Subjected to High Impact Loading;590
25.1.3.7;3.7 Dynamic Crack Kinking and Penetration at an Interface;591
25.1.3.7.1;3.7.1 Weak Interfaces with Different Interfacial Angles;591
25.1.3.7.2;3.7.2 Modeling of Dynamic Failure Modes Across an Interface;593
25.1.3.7.3;3.7.3 Mode Mixity of the Kinked Interfacial Crack;595
25.1.3.8;3.8 Two-layer Specimens with Direct Impact on the BrittlePolymeric Layer;597
25.1.4;4 Conclusions;598
25.1.5;References;599
26;Chapter 23;602
26.1;Characterization of Fatigue Behavior of Composite Sandwich Structures at Sub-Zero Temperatures;602
26.1.1;1 Introduction;602
26.1.2;2 Experiments;604
26.1.2.1;2.1 Specimens;604
26.1.2.2;2.2 Static Flexure Tests;604
26.1.2.3;2.3 Flexural Fatigue Tests;606
26.1.3;3 Finite Element Modeling;608
26.1.4;4 Results;609
26.1.4.1;4.1 Static 4-Point Bending;609
26.1.4.2;4.2 Flexural Fatigue;611
26.1.4.3;4.3 Fatigue Life at Low Temperatures;611
26.1.4.4;4.4 Stiffness and Damping at Low Temperatures;612
26.1.4.5;4.5 Fatigue Failure Modes;617
26.1.5;5 Finite Element Analysis;617
26.1.6;6 Conclusions;619
26.1.7;References;620
27;Chapter 24;622
27.1;Impact and Blast Resistance of Sandwich Plates ;622
27.1.1;1 Introduction;623
27.1.2;2 Response to Uniform Pressure;624
27.1.3;3 Response to Impact;627
27.1.3.1;3.1 Medium Velocity Impact at Different Contact Locations;627
27.1.3.2;3.2 Response to Impact at Support;630
27.1.3.3;3.3 Effect of Indenter Shape, Interlayer Moduli and Thickness;632
27.1.3.4;3.4 Energy Released by Interfacial Cracks;637
27.1.4;4 Response to Impulse or Blast Loads;640
27.1.4.1;4.1 Geometry and Material Properties;641
27.1.4.2;4.2 Finite Element Models;645
27.1.4.3;4.3 Response to a Full Span Pressure Impulse;646
27.1.4.4;4.4 Energy Absorption;649
27.1.4.5;4.5 Effect of Change in Total Mass;651
27.1.4.6;4.6 Performance Comparison of Polyurea and Polyurethane;651
27.1.5;5 Conclusions;652
27.1.6;References;653
28;Chapter 25;657
28.1;Modeling Blast and High-Velocity Impact of Composite Sandwich Panels;657
28.1.1;1 Introduction;657
28.1.2;2 Impulsively-Loaded Sandwich Panels;658
28.1.2.1;2.1 Phase I – Through-Thickness Wave Propagation;660
28.1.2.1.1;2.1.1 Transmission and Reflection at Interfaces;660
28.1.2.1.2;2.1.2 Elastic and PlasticWaves in Foam;662
28.1.2.1.3;2.1.3 Local Indentation;663
28.1.2.2;2.2 Phase II – Global Bending/Shear;664
28.1.2.2.1;2.2.1 System Lagrangian;665
28.1.2.2.2;2.2.2 Bending/Shear Strain Energy Potential;665
28.1.2.2.3;2.2.3 Equations of Motion;666
28.1.2.3;2.3 Transient Deformations;667
28.1.2.3.1;2.3.1 Local Core Crushing: Phase I Response;668
28.1.2.3.2;2.3.2 Global Bending/Shear: Phase II Response;670
28.1.2.4;2.4 Damage Initiation;670
28.1.3;3 High-Velocity Impact of Sandwich Panels;673
28.1.3.1;3.1 Phase I: Local Indentation;675
28.1.3.1.1;3.1.1 Through-Thickness Wave Propagation;675
28.1.3.1.2;3.1.2 Local Indentation;675
28.1.3.1.2.1;Kinetic Energy;676
28.1.3.1.2.2;Potential Energy;677
28.1.3.1.2.3;Equation of Motion;678
28.1.3.2;3.2 Phase II: Global Bending/Shear;679
28.1.3.2.1;3.2.1 Kinetic Energy;680
28.1.3.2.2;3.2.2 Global Bending/Shear Energy;680
28.1.3.2.3;3.2.3 Equations of Motion;681
28.1.3.3;3.3 Comparison with Finite Element Analysis;682
28.1.4;4 Conclusions;683
28.1.4.1;Appendix A Uniaxial StrainWave Speed in an Orthotropic Plate;683
28.1.4.2;Appendix B Momentum and Kinetic Energy of Core During Phase I;684
28.1.4.3;Appendix C Elastic Strain Energy and Plastic Work in Core;685
28.1.5;References;686
29;Chapter 26;687
29.1;Effect of Nanoparticle Dispersion on Polymer Matrix and their Fiber Nanocomposites;687
29.1.1;1 Introduction;687
29.1.2;2 Effect of Dispersion on Polymer Matrix;688
29.1.2.1;2.1 Materials;691
29.1.2.2;2.2 Fabrication;691
29.1.2.3;2.3 Microstructural and Mechanical Characterization Techniques;692
29.1.2.4;2.4 Morphological Characterization;692
29.1.2.5;2.5 Mechanical Characterization;694
29.1.3;3 Mechanical Behavior of FRP Nanocomposites;695
29.1.3.1;3.1 Materials and Fabrication;698
29.1.3.2;3.2 Mechanical Characterization Techniques;698
29.1.3.2.1;3.2.1 Compression;698
29.1.3.2.2;3.2.2 Tension;699
29.1.3.2.3;3.2.3 DCB;699
29.1.3.2.4;3.2.4 ENF;699
29.1.3.2.5;3.2.5 Low Velocity Impact;699
29.1.3.3;3.3 Compressive Properties;699
29.1.3.3.1;3.3.1 Off-Axis Compressive Strength;699
29.1.3.3.2;3.3.2 Longitudinal Compressive Strength;700
29.1.3.4;3.4 Tensile Properties;702
29.1.3.5;3.5 Fracture Toughness;703
29.1.3.6;3.6 Impact Resistance;705
29.1.4;4 Conclusion;706
29.1.5;References;707
30;Chapter 27;710
30.1;Experimental and Analytical Analysis of Mechanical Response and Deformation Mode Selection in BalsaWood;710
30.1.1;1 Introduction;711
30.1.2;2 Experimental;712
30.1.2.1;2.1 Microstructural Features of Balsa Wood;712
30.1.2.2;2.2 Specimen Preparation and Geometry;714
30.1.2.3;2.3 Quasi-Static Testing Method;715
30.1.2.4;2.4 Dynamic Testing Method;716
30.1.3;3 Results and Discussion;717
30.1.3.1;3.1 Stress–Strain Response;717
30.1.3.1.1;3.1.1 End Effects;719
30.1.3.1.2;3.1.2 Initial Failure and Progressive Deformation;719
30.1.3.1.3;3.1.3 Densification;721
30.1.3.1.4;3.1.4 Energy Dissipation Capacity;724
30.1.3.2;3.2 Failure Modes;726
30.1.3.3;3.3 Strength Models Based on Failure Modes;727
30.1.3.3.1;3.3.1 Elastic Buckling;727
30.1.3.3.2;3.3.2 Plastic Buckling;729
30.1.3.3.3;3.3.3 End-Cap Collapse;729
30.1.3.3.4;3.3.4 Kink Band Formation;730
30.1.3.4;3.4 Comparison with Quasi-Static Experiments;731
30.1.3.5;3.5 Models for Inertial Stress Enhancement;732
30.1.3.5.1;3.5.1 Background;732
30.1.3.5.2;3.5.2 Buckling;734
30.1.3.5.2.1;Model Parameters;738
30.1.3.5.3;3.5.3 Kink Band Formation;739
30.1.3.5.3.1;Model Parameters;741
30.1.3.5.4;3.6 Comparison of Inertia-Based Models with Dynamic Data;741
30.1.4;4 Conclusions;745
30.1.5;References;747
31;Chapter 28;749
31.1;Mechanics of PAN Nanofibers;749
31.1.1;1 Introduction;749
31.1.2;2 Experimental Methods and Materials;751
31.1.2.1;2.1 Nanofiber Fabrication;751
31.1.2.2;2.2 Mechanical Experiments with Single Polymeric Nanofibers;752
31.1.2.2.1;2.2.1 Background;752
31.1.2.2.2;2.2.2 Nanoscale Tension Experiments with Individual Polymeric Nanofibers;753
31.1.2.2.3;2.2.3 Resolution in Force and Nanofiber Extension Measurements;754
31.1.2.2.4;2.2.4 Loadcell Calibration;756
31.1.3;3 Fabrication vs Mechanical Behavior of PAN Nanofibers;757
31.1.4;4 Mechanical Instabilities During Cold Drawing of PAN Nanofibers;760
31.1.5;5 Effect of Strain Rate on the Mechanical Deformation of Nanofibers;761
31.1.6;6 Origins of Surface Rippling in Electrospun PAN Nanofibers;763
31.1.7;7 Molecular Alignment in Electrospun PAN Nanofibers;765
31.1.8;8 Conclusions;767
31.1.9;References;767
32;Chapter 29;771
32.1;Characterization of Deformation and Failure Modes of Ordinary and Auxetic Foams at Different Length Scales;771
32.1.1;1 Introduction;771
32.1.2;2 The Multi-scale Speckle Photography Technique;772
32.1.3;3 Studies of Ordinary Foams;774
32.1.3.1;3.1 Size Effect on Mechanical Properties of Foam Composites;774
32.1.3.2;3.2 Crack Tip Deformation in Foam at Different Length Scales;778
32.1.4;4 Studies of Auxetic Foams;781
32.1.4.1;4.1 Introduction;781
32.1.4.2;4.2 Auxetic Polyurethane Foam;782
32.1.4.3;4.3 Auxetic PVC (H45) Foam;782
32.1.4.3.1;4.3.1 Manufacturing the Auxetic PVC Foam;782
32.1.4.3.2;4.3.2 Mechanical Properties of Auxetic PVC Foam;783
32.1.4.3.2.1;Uniaxial Test;783
32.1.4.3.2.2;Shear Test;786
32.1.4.3.2.3;Impact Test;787
32.1.4.3.2.4;Indentation Tests;787
32.1.5;References;789
33;Chapter 30;791
33.1;Fracture of Brittle Lattice Materials: A Review;791
33.1.1;1 Introduction;791
33.1.1.1;1.1 Fracture Mechanics Concepts;792
33.1.1.2;1.2 Outline of this Review;793
33.1.2;2 Classical Beam Theory;793
33.1.2.1;2.1 The Hexagonal Lattice;794
33.1.2.2;2.2 Other 2D Lattices;795
33.1.2.3;2.3 Statistics of Brittle Failure;795
33.1.3;3 Generalised Continuum Theories;796
33.1.4;4 Finite Element Modelling;797
33.1.4.1;4.1 Stress Analysis;797
33.1.4.2;4.2 Boundary Layer Analysis;799
33.1.4.2.1;4.2.1 Extrapolation of 2D Results to 3D Lattices;802
33.1.4.2.2;4.2.2 Sensitivity of Fracture Toughness to Imperfections;802
33.1.5;5 Atomic Lattice Models for Crack Dynamics;803
33.1.6;6 Representative Cell Method;804
33.1.7;7 Experimental Studies on Fracture Toughness;805
33.1.8;8 Concluding Remarks;806
33.1.9;References;806
34;Author Index;809