Advances in the Bonded Composite Repair of Metallic Aircraft Structure
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Table of contents
- Title Pageiii
- Copyright Pageiv
- Contentsxiii
- Biographiesv
- Forewordvii
- Dedicationix
- Volume 11
- Chapter 1. Introduction and Overview1
- 1.1. Aim of book1
- 1.2. Classification of aircraft structures for inspection and repair2
- 1.3. Repair requirements5
- 1.4. Repair procedures6
- 1.5. The case for adhesively bonded repairs7
- 1.6. Composite versus metallic patches9
- 1.7. Scope of applications10
- 1.8. Some experimental comparisons of bonding versus bolting11
- 1.9. R&D requirements14
- 1.10. Conclusion17
- References17
- Chapter 2. Materials Selection and Engineering19
- 2.1. Introduction19
- 2.2. Materials for patches and reinforcements21
- 2.3. Adhesive systems28
- 2.4. Primers and coupling agents32
- 2.5. Adhesive and composite test procedures34
- 2.6. Materials engineering considerations35
- References39
- Chapter 3. Surface Treatment and Repair Bonding41
- 3.1. Introduction41
- 3.2. Mechanical tests45
- 3.3. Standard tests47
- 3.4. Fundamentals of durable bonding48
- 3.5. Requirements of surface preparation56
- 3.6. Adhesive application64
- 3.7. Surface treatment quality control66
- 3.8. Surface preparations for aluminium adherends69
- 3.9. Surface preparations for titanium adherends74
- 3.10. Surface preparations for steel adherends77
- 3.11. Surface preparations for thermosetting-matrix composites78
- 3.12. Recent surface preparation research80
- References82
- Chapter 4. Adhesives Characterisation and Data Base87
- 4.1. Introduction87
- 4.2. Common ASTM and MIL tests88
- 4.3. Fatigue loading94
- 4.4. Fracture-mechanics allowables94
- 4.5. FM73 database98
- References101
- Chapter 5. Fatigue Testing of Generic Bonded Joints103
- 5.1. Introduction103
- 5.2. The DOFS104
- 5.3. The skin doubler specimen114
- 5.4. Discussion124
- References125
- Chapter 6. Evaluating Environmental Effects on Bonded Repair Systems Using Fracture Mechanics127
- 6.1. Introduction127
- 6.2. Materials and specimens128
- 6.3. Experimental procedures129
- 6.4. Analysis131
- 6.5. Results and discussion132
- 6.6. Summary and conclusions135
- References135
- Chapter 7. Analytical Methods for Designing Composite Repairs137
- 7.1. Introduction137
- 7.2. Formulation and notation139
- 7.3. Load transfer of bonded reinforcement141
- 7.4. Symmetric repairs144
- 7.5. Shear mode155
- 7.6. One-sided repairs157
- 7.7. Residual thermal stress due to adhesive curing167
- References174
- Chapter 8. Recent Expansions in the Capabilities of Rose’s Closed-form Analyses for Bonded Crack-p177
- 8.1. Introduction177
- 8.2. Universal efficiency charts for isotropic patches183
- 8.3. Equivalence between octagonal and elliptical patch shapes184
- 8.4. Effects of patch tapering on the adhesive stresses186
- 8.5. Universal charts for the effects of corrosion189
- 8.6. Design of patches to compensate for corrosion damage190
- 8.7. Analysis of patches over cracks in stiffened panels191
- 8.8. Designing to avoid crack initiation194
- 8.9. Universal efficiency charts for orthotropic patches196
- 8.10. Effects of residual thermal stresses on bonded repairs197
- 8.11. Effects of adhesive non-linearity and disbonds on crack-tip stress-intensity factors200
- 8.12. Out-of-plane bending effects with one-sided patches202
- 8.13. Remaining challenges involving closed-form analyses204
- 8.14. Concluding remarks204
- References205
- Chapter 9. Numerical Analysis and Design207
- 9.1. Analysis and design207
- 9.2. The 2D finite element formulation208
- 9.3. Initial design guidelines215
- 9.4. Comparison with experimental results for non rib stiffened panels227
- 9.5. Repair of thick sections229
- 9.6. Repair of cracked holes in primary structures233
- 9.7. Repair of cracked lugs236
- 9.8. Repairs to interacting surface flaws242
- 9.9. Material nonlinearities243
- 9.10. Effect of variable adhesive thickness251
- 9.11. Repairs to cracked holes under bi-axial loading258
- 9.12. Findings relevant to thick section repair262
- References266
- Chapter 10. Shape Optimisation for Bonded Repairs269
- 10.1. Introduction269
- 10.2. Analytical formulation for improved stepping in patch taper region272
- 10.3. FE analysis for adhesive stress and plate stress concentration281
- 10.4. Gradientless FE method for optimal through-thickness shaping285
- 10.5. Sensitivity FE method for optimal joint through-thickness shaping288
- 10.6. Optimal through-thickness shaping for F/A-18 bulkhead reinforcement297
- 10.7. Optimisation for F/A-18 aileron hinge reinforcement300
- 10.8. In-plane shaping effects308
- 10.9. Conclusions313
- References314
- Chapter 11. Thermal Stress Analysis317
- 11.1. Introduction317
- 11.2. Analytical expression for initial stresses in a circular plate due to heating318
- 11.3. Finite element thermal stress analysis335
- 11.4. Application of analysis to large repairs of aircraft wings341
- 11.5. Conclusions349
- 11.6. Acknowledgment350
- References350
- Appendix351
- Chapter 12. Fatigue Crack Growth Analysis of Repaired Structures353
- 12.1. Introduction353
- 12.2. Crack-closure analysis of repaired cracks354
- 12.3. Overload effect and validation using finite element method361
- 12.4. Thermal residual stresses and comparison with experimental results365
- 12.5. Conclusions372
- References373
- Chapter 13. Boron/epoxy Patching Efficiency Studies375
- 13.1. Introduction375
- 13.2. Stress intensity analysis of patched cracks376
- 13.3. Experimental approach379
- 13.4. Fatigue studies381
- 13.5. An approach to b/ep patch design392
- References396
- Chapter 14. Glare Patching Efficiency Studies399
- 14.1 Introduction399
- 14.2. Parametric studies of various patch materials400
- 14.3. Experimental results408
- 14.4. Discussion410
- 14.5. Summary and conclusions412
- References413
- Chapter 15. Graphite/epoxy Patching Efficiency Studies415
- 15.1. Introduction415
- 15.2. Repair of thin skin components416
- 15.3. Repair of thick sections418
- 15.4. Graphite/epoxy versus boron/epoxy424
- 15.5. Effect of bondline defects427
- 15.6. Effect of impact damage433
- 15.7. Effect of service temperature435
- 15.8. Effect of exposure to hot-wet environments436
- 15.9. Repair of battle damage438
- 15.10. Future work440
- 15.11 Acknowledgements440
- References441
- Chapter 16. Repair of Multi-site Damage443
- 16.1. Introduction443
- 16.2. Specimen and loading444
- 16.3. Repairs450
- 16.4. Stress analyses453
- 16.5. Specimen fatigue test results459
- 16.6. Damage tolerant evaluation of specimens468
- 16.7. Full scale repair demonstrators474
- 16.8. Conclusions480
- References482
- Chapter 17. Damage Tolerance Assessment of Bonded Composite Doubler Repairs for Commercial Aircraft485
- 17.1. Introduction485
- 17.2. Composite doubler damage tolerance tests491
- 17.3. Conformity inspection and FAA oversight492
- 17.4. Test results500
- 17.5. Conclusions514
- References515
- Chapter 18. Validation of Stress Intensity Estimations in Patched Panels517
- 18.1. Introduction517
- 18.2. The K-gauge518
- 18.3. Theory of KI measurement using strain gauges519
- 18.4. Experimental procedure522
- 18.5. Strain surveys524
- 18.6. Crack length526
- 18.7. Time-dependent behaviour527
- 18.8. Conclusions529
- 18.9. Nomenclature529
- References530
The availability of efficient and cost-effective technologies to repair or extend the life of aging military airframes is becoming a critical requirement in most countries around the world, as new aircraft becoming prohibitively expensive and defence budgets shrink. To a lesser extent a similar situation is arising with civil aircraft, with falling revenues and the high cost of replacement aircraft.
This book looks at repair/reinforcement technology, which is based on the use of adhesively bonded fibre composite patches or doublers and can provide cost-effective life extension in many situations. From the scientific and engineering viewpoint, whilst simple in concept, this technology can be quite challenging particularly when used to repair primary structure. This is due to it being based on interrelated inputs from the fields of aircraft design, solid mechanics, fibre composites, structural adhesive bonding, fracture mechanics and metal fatigue. The technologies of non-destructive inspection (NDI) and, more recently smart materials, are also included. Operational issues are equally critical, including airworthiness certification, application technology (including health and safety issues), and training.
Including contributions from leading experts in Canada, UK, USA and Australia, this book discusses most of these issues and the latest developments. Most importantly, it contains real histories of application of this technology to both military and civil aircraft.