Rajapakse / 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: Wasserzeichen (»Systemvoraussetzungen)

E-Book, Englisch, 818 Seiten

This book collects major research contributions in composite materials and sandwich structures supported by the U.S. Office of Naval Research. It contains over thirty chapters written by experts and serves as a reference and guide for future research.

Autoren/Hrsg.

Rajapakse, Y.

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