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 |  موضوع: رسالة ماجستير Investigation of Composite Patch Performance Under Low-Velocity Impact Loading السبت 03 أكتوبر 2020, 12:45 am | |
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أخوانى فى الله
أحضرت لكم كتاب
رسالة ماجستير بعنوان
Investigation of Composite Patch Performance Under Low-Velocity Impact Loading
A Thesis Presented for the Master of Science Degree
The University of Tennessee, Knoxville
Geoffrey Roy Goodmiller
و المحتوى كما يلي :
TABLE OF CONTENTS
CHAPTER I INTRODUCTION 1
1.1 Composite Patch Repair 1
1.2 Research Objectives .3
1.3 Overview of Technical Approach .5
Composite Approach .6
Adhesive Approach .7
Metal Approach .8
Hybrid Model Approach .8
CHAPTER II LITERATURE REVIEW .9
2.1 Hybrid/Repair Patch Applications 9
Aerospace Industry Applications 9
Civil Engineering Applications 10
Naval Applications .11
2.2 Impact Damage in Composites 12
2.3 Impact Modeling of Composites .15
2.4 Disbonds between Composite and Metal .17
2.5 Impact on Hybrid Structures 18
2.6 Impact on Fiber-Metal Laminates 20
CHAPTER III DAMAGE MODEL VALIDATIONS .23
3.1 Introduction 23
3.2 Intralaminar Damage Model 24
Selection of Damage Model .24vi
Failure Criteria .26
Damage Evolution .27
Material Properties 31
3.3 Interlaminar Damage Model 32
Selection of Damage Model .32
Cohesive Zone Theory 34
Coarse Mesh Adjustment 37
Mixed-Mode Damage Model 37
Damage Initiation, Evolution, and Viscosity .39
Parameter Study & Validation 41
Double Cantilever Beam Test 42
Mixed-Mode Bending Test .46
Selection of Parameters 48
3.4 Low-Velocity Impact on Composite 49
Finite Element Model .49
Validation Results 51
3.5 Adhesive Layer Damage Model .54
Selection of Damage Model .54
Validation Results 55
3.6 Metal Damage Model 59
Selection of Damage Model .59
Validation Results 60
CHAPTER IV HYBRID MODEL VALIDATION 63
4.1 Material Properties 63vii
Composite Properties 64
Metal and Adhesive Material Properties 66
4.2 Experimental and FEA Setup 66
4.3 Validation Results 68
CHAPTER V SENSITIVITY STUDY .73
5.1 Parameters Studied .73
5.2 Fiber Volume Ratio 73
5.3 Ply Thickness 76
5.4 Other Parameters 77
CHAPTER VI CONCLUSIONS AND RECOMMENDATIONS .80
6.1 Strengths and Weaknesses of Model 80
6.2 Future Work .82
LIST OF REFERENCES .84
APPENDIX 91
A.1 Derivation of Material Properties .92
A.2 DCB Theoretical Solution 93
A.3 MMB Theoretical Solution .94
VITA 96viii
LIST OF TABLES
Table 1. Material properties for E-glass/epoxy lamina (Vf = 0.60) .32
Table 2. Material properties for AS4/3501-6 .43
Table 3. Cohesive element properties for E-glass/epoxy lamina .49
Table 4. Material Properties for 0.2 mm thick Araldite 2015 adhesive 56
Table 5. Material properties for AA5083-H116 aluminum .60
Table 6. Comparison of deflections from FE and laboratory data .61
Table 7. Material properties for E-glass fibers 64
Table 8. Material properties for Scott Bader Crystic 272 matrix 65
Table 9. Calculated material properties for E-glass/polyester composite 65
Table 10. Cohesive element properties for E-glass/polyester .65
Table 11. Material properties for SUS304 stainless steel .66
Table 12. Comparison of FEA results to experimental data 69
Table 13. Material Properties for E-glass/polyester composite with varying fiber volume
ratios .74
Table 14. Comparison of FEA results for varying Vf 75
Table 15. Comparison of FEA results for varying ply thickness 76
Table 16. Material properties for SUS304 stainless steel – Option 2 78
Table 17. Comparison of FEA results for various parameters .79ix
LIST OF FIGURES
Figure 1. Anatomy of a composite patch 1
Figure 2. Diagram of resin-rich layer between plies 6
Figure 3. Local lamina element orientation convention .25
Figure 4. General stress-displacement curve for lamina damage .28
Figure 5. Bi-linear traction separation law .35
Figure 6. Diagram of mixed-mode traction-separation model .38
Figure 7. Calculation and application of damage variable, D 40
Figure 8. DCB test setup 42
Figure 9. Effect of interfacial strength on the load-deflection curve for DCB (0.5 mm
mesh, K = 100,000; μ = 0.0001) 43
Figure 10. Effect of penalty stiffness, K (MPa/mm), on load-deflection curve for DCB
(0.5 mm mesh, Ne = 3, μ = 0.001) 44
Figure 11. Effect of viscosity, μ, on load-deflection curve for DCB (0.5 mm mesh, K =
100,000, Ne = 3) .45
Figure 12. MMB test setup .45
Figure 13. Effect of interface strength on load-displacement curve for MMB (K =
250,000, μ = 0.0001) .46
Figure 14. Effect of penalty stiffness on load displacement curve for MMB (Ne = 8, μ =
0.0001) 47
Figure 15. MMB load-deflection curve for selected cohesive element parameters for Eglass/epoxy .48x
Figure 16. Mesh for ply layers (left) and cohesive layers (right) 50
Figure 17. Comparison of absorbed energy for validation (20 J) .51
Figure 18. Comparison of contact force for validation – 20 J 52
Figure 19. Delamination in cohesive layers from top (top right) to bottom (bottom
middle) at time = 0.88 ms 53
Figure 20. Delamination and ply damage in composite at time = 11 ms .53
Figure 21. Trapezoidal traction-separation law .54
Figure 22. DCB load-deflection curve for adhesive validation .57
Figure 23. ENF test setup .58
Figure 24. ENF load-deflection curve for adhesive validation .58
Figure 25. Comparison of FEM and experimental time history deflections for aluminum
impact 62
Figure 26. Residual stresses at areas of plastic deformation 62
Figure 27. Stresses at maximum deformation during impact 62
Figure 28. Hybrid composite configuration for Akimoto et al. 63
Figure 29. Load-deflection for hybrid composite validation .68
Figure 30. Contact force – time curve for FEA 70
Figure 31. Energy-time curve for FEA 70
Figure 32. Delamination between ply 1 and 2 (left), 2 and 3 (middle), 3 and 4 (right) at
time = 4 ms 71
Figure 33. Adhesive damage in validation FEA at time = 4 ms .71
Figure 34. Section through middle of plate at maximum deflection (top) and time = 4 ms
(bottom) .72
Figure 35. Load-deflection curve for varying values of Vf 75xi
Figure 36. Load-deflection curve for varying values of ply thickness 77
Figure 37. Finer mesh for sensitivity analysis .78
Figure 38. Load-deflection curve for various parameters 79
Figure 39. Hourglassing in one element through thickness (top) and three elements
through thickness (bottom) 8
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