Damage Growth in Aerospace Composites (eBook)

Aniello Riccio is Adjunct Professor of Aerospace Engineering at Second University of Naples, Italy.

Contents 6
1 Introduction 8
1.1 State of the Art of European Projects on Composites Damage Management 8
1.2 AG-32 Objectives and Relationships with Previous Projects 11
1.3 AG-32 Work Breakdown Structure and Presentation of Results 12
Part I Detailed Methodologies for Damage Growth in Aerospace Composites 14
2 Detailed Methodologies for Integrated Delamination Growth and Fiber-Matrix Damage Progression Simulation 15
2.1 Introduction 15
2.2 Objectives 17
2.3 Description of the Method 18
2.3.1 Phenomenology 18
2.3.2 Theoretical Background 20
2.3.2.1 Intra-laminar Damage: A Progressive Damage Procedure 20
2.3.2.2 Stress Evaluation 20
2.3.2.3 Failure Criteria and Material Properties Degradation Rules 21
2.3.2.4 Inter-laminar Damage: Energy Release Rate and Crack Growth Criteria 23
2.3.3 Numerical Implementations in B2000 24
2.3.3.1 Progressive Damage Brick Element 25
2.3.3.2 Interface Fracture Element for Delamination Growth 26
2.3.3.3 Contact Element 28
2.3.4 Numerical Tool for Intra-laminar Damage and Delamination Growth 28
2.3.5 Benefits and Limitations of the Method and Added Value with Respect to the State of the Art 30
2.4 Validation of the Developed Numerical Tools: B2000 Applications 31
2.4.1 Tension-Loaded Laminate with Hole 31
2.4.2 Composite Delaminated Panels Loaded in Compression 34
2.4.3 Specimen Configuration #SS3 38
2.4.4 Specimen Configuration #SS4 42
2.4.5 Specimen Configuration #SS5 45
2.5 ABAQUSTM Exploratory Applications: Stiffened Panels with Embedded Delaminations and a Skin-Stringer Debonding 47
2.5.1 Simulating the Damage Onset and Evolution in ABAQUS 48
2.5.1.1 Inter-laminar Damage 48
2.5.1.2 Intra-Laminar Damage 49
2.5.2 Stiffened Panel with an Embedded Bay Delamination 50
2.5.3 Stiffened Panel with an Skin-Stringer Debonding 56
References 64
3 Delamination and Debonding Growth in Composite Structures 68
3.1 Introduction 68
3.2 Delamination Growth 70
3.2.1 Virtual Crack Closure Technique Fundamentals 71
3.2.2 Validation Benchmark Definition 72
3.2.3 FE Model Definition and Buckling Simulations 72
3.2.4 Delamination Growth Algorithm 75
3.2.5 Correlation Between FE Simulations and Tests 77
3.2.6 Mesh Size Effect 78
3.2.7 Comparison Among Mixed-Mode Failure Criteria 78
3.2.8 Conclusions and Future Work 80
3.3 Debonding Growth 81
3.3.1 FE Modelling of DCB Coupons 82
3.3.2 Cohesive Zone (CZ) Elements 83
3.3.3 Mesh Dependency 84
3.3.4 Experimental Results on DCB Coupons 86
3.3.5 Correlation FE Model Simulation—Tests—DCB Coupons 88
3.3.6 Conclusions and Future Work 91
References 92
4 Delamination Growth in Composite Plates Under Fatigue Loading Conditions 94
4.1 Introduction 94
4.2 Fatigue Degradation: Linear Approach 95
4.3 Fatigue Degradation: Non-linear Approach 97
4.4 Numerical Application: Delamination Growth in a Composite Panel Subjected to Fatigue Load 99
4.5 Numerical Application: Sensitivity Analysis of Damage Propagation of a Delaminated Composite Panel Under Fatigue Load 104
4.6 Conclusions 109
References 109
5 Influence of Intralaminar Damage on the Delamination Crack Evolution 111
5.1 Introduction 111
5.2 Influence of Intralaminar Damage on the Interlaminar Damage Evolution 113
5.2.1 Influence of Intralaminar Damage on Delamination Crack Onset 113
5.2.1.1 Identification of the Intrinsic Out-of-Plane Tensile Strength 113
5.2.1.2 Determination of the Influence of Intralaminar Damages on the Onset of Delamination 117
5.2.2 Influence of Intralaminar Damage on Delamination Crack Propagation 119
5.2.2.1 The Tensile Flexure Test on Notched Specimen 120
Description of the Experimental Procedure 120
Description of the Experimental Device 121
Experimental Observations 122
Identification of the Interface Toughness in a T700GCM21 CarbonEpoxy Laminate 123
5.2.2.2 Demonstration of the Influence of Intralaminar Damage on the Interfacial Fracture Toughness 124
5.3 Modeling the Effect of Intralaminar Damage on the Interlaminar Damage Evolution 126
5.3.1 Cohesive Zone Model for Modeling the Interlaminar Damage 126
5.3.1.1 General Framework of the Cohesive Zone Model 126
5.3.1.2 Damage Evolution Law of the Interlaminar Damage 128
5.3.1.3 Determination of the Onset Criterion with Reinforcement of the Interfacial Strengths Under Out-of-Plane CompressionShearing Loadings 129
5.3.2 Damage Evolution Law of Intralaminar Damage 132
5.3.3 Damage Evolution Law of Delamination Including the Intralaminar Damage Effect 135
5.3.4 Implementation in a Finite Element Code 136
5.4 Application on Structural Test Cases 137
5.5 Conclusions 140
References 141
6 Microdamage Modeling in Laminates 145
6.1 Introduction 145
6.2 Experimental Methods for Damage State Characterization 150
6.3 Damage Initiation and Growth 154
6.3.1 Initiation Stress and Propagation Stress 154
6.3.2 Statistical Nature of Initiation Stress Distribution 157
6.3.3 Energy Release Rate Based Analysis of Intralaminar Crack Propagation 162
6.4 Stiffness of Damaged Laminate 168
6.4.1 Calculation Expressions 168
6.4.2 Examples of Calculation and Experiments 170
6.5 Conclusions 173
References 175
Part II Fast Methodologies for Damage Growth in Aerospace Composites 178
7 Finite Element Study of Delaminations in Notched Composites 179
7.1 Finite Element Delamination Study of a Notched Composite Plate 179
7.1.1 Element Type, Mesh, Boundary Condition and Applied Load 181
7.1.2 Assumption and Particular Settings 181
7.1.3 Method 182
7.2 Results 182
7.2.1 Structural Response 182
7.2.2 Delamination 183
7.2.2.1 Delamination Initiation 183
7.2.2.2 Delamination Growth 184
7.3 Comparison and Discussion 185
7.4 Conclusions 186
References 187
8 Effect of the Damage Extension Through the Thickness on the Calculation of the Residual Strength of Impacted Composite Laminates 188
8.1 Introduction 188
8.2 Delamination Buckling and Growth 190
8.2.1 Delamination Buckling Theory 191
8.2.2 Approximate Calculation of Strain Energy Release Rate 192
8.3 Characterization of Damage 194
8.3.1 Numerical Implementation 194
8.3.2 Description of Method 195
8.3.3 Analytical Tool to Predict Damage Extension 197
8.4 Benefits and Limitations of the Method and Added Value with Respect to the State of the Art 199
References 199
9 A Fast Numerical Methodology for Delamination Growth Initiation Simulation 200
9.1 Introduction 200
9.2 Description of the Method: Theoretical Background 203
9.3 Finite Element Implementation 211
9.4 Numerical Application: Sensitivity Analysis on a Stringer-Stiffened Panel with an Embedded Delamination 213
9.5 Benefits and Limitations of the Method and Added Value with Respect to the State of the Art 216
References 219
Part III Manufacturing and Testing 222
10 An Experimental Study on the Strength of Out of Plane Loaded Composite Structures 223
10.1 Introduction 223
10.2 Mechanical Tests 224
10.2.1 Bending and Compressions Tests 224
10.2.2 Inspection—NDT and Fractography 225
10.3 Experimental Results 226
10.3.1 Bending Tests of Impacted Laminates 227
10.3.2 Bending Test of Notched Laminates 228
10.3.3 Fractoraphic Results 228
10.4 Conclusions 229
References 230
11 Buckling and Collapse Tests Using Advanced Measurement Systems 231
11.1 Introduction 231
11.2 Definitions 232
11.3 DLR Buckling Test Facility 233
11.4 Preparation of the Test Structures 235
11.5 Advanced Measurement Systems 236
11.5.1 Before the Test 236
11.5.1.1 Non-destructive Testing and Thickness Measurement 236
11.5.1.2 ATOS System—Optical Measurement of Imperfections 236
11.5.2 During the Test 237
11.5.2.1 ARAMIS System—Optical Measurement of Deformations 237
11.5.2.2 Thermography—Measurement of Degradation 239
11.5.2.3 Lamb-Waves—Measurement of Degradation 240
11.6 Material Properties 241
11.7 Test Results 242
11.7.1 Cyclic Tests and Collapse Test of a Stiffened Panel 242
11.7.2 Buckling Test of an Unstiffened Cylinder 247
References 248
12 Vacuum Infusion Manufacturing of CFRP Panels with Induced Delamination 249
12.1 Introduction 249
12.2 Liquid Composite Molding Overview 250
12.3 Experimental Activity 255
12.3.1 FRCP Manufacturing 255
12.3.2 Microscopy Analysis 259
12.4 Conclusions 259
References 261
13 Lock-in Thermography to Detect Delamination in Carbon Fibres Reinforced Polymers 262
13.1 Introduction 262
13.2 Non-destructive Testing with IRT 263
13.2.1 Basics on Lockin Thermography 264
13.3 Experimental Analysis 265
13.3.1 Specimens Preparation 265
13.3.2 Test Setup 266
13.4 Results and Discussion 268
13.4.1 Qualitative Analysis 269
13.4.2 Quantitative Analysis 273
13.5 Conclusions 276
References 277