Advances in the Bonded Composite Repair of Metallic Aircraft Structure, 2 Volume Set

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. Cover......Page 1 Half Title Page......Page 4 Title Page......Page 6 Copyright......Page 7 Biographies......Page 8 Acknowledgement......Page 9 Foreword......Page 10 Dedication......Page 12 Subscripts/Superscripts......Page 14 Table of Contents......Page 16 19.1. Introduction......Page 34 19.2. Cracking History......Page 36 19.3. Sound Pressure Levels......Page 39 19.4. Random Response Analysis......Page 40 19.5. Stress Intensity Factors......Page 41 19.6. FEA of Cracked Nacelle Inlet......Page 42 19.7. Highly Damped Repairs for Cracked Panels......Page 49 19.8. Aft Fuselage Finite Element Model......Page 60 19.9. Thermal Environment for F/A-18......Page 65 19.10. Analytical Results......Page 66 19.11. Experimental Work......Page 69 19.12. Conclusions for Aft Fuselage Repair......Page 71 20.1. Introduction......Page 74 20.2. Smart Patch Approach......Page 76 20.3. Damage Detection Studies......Page 81 20.4. Laboratory Smart Patch Conceptional Demonstrators......Page 102 20.5. In-Flight Demonstrator......Page 107 20.6. Conclusions......Page 114 21.1. Introduction......Page 118 21.2. Certification of an Adhesively Bonded Repair......Page 120 21.3. Repair Design Information......Page 122 21.4. Analysis and Development Testing......Page 124 21.6. In-Service Management and Inspection......Page 140 21.8. Conclusions......Page 141 22.1. Current Limitations of Crack Patching......Page 146 22.2. Justifying Credit for Patching Efficiency - Fatigue Concerns......Page 147 22.3. Justifying Credit for Patching Efficiency - Environmental Durability Concerns......Page 151 22.4. Justifying Credit for Patching Efficiency - the Smart Patch Approach......Page 157 22.5. Discussion......Page 158 22.6. Conclusions......Page 159 23.1. Introduction......Page 162 23.2. Inspection for Delaminations, Disbonds and Adhesion Failure......Page 167 23.3. Inspections for Cracks in Parent Material beneath Composite Doublers......Page 197 23.4. Quality Control Issues in Service......Page 217 23.5. Conclusions......Page 222 23.6. Acknowledgements......Page 226 24.1. Introduction......Page 230 24.2. Repair Application Technology......Page 233 24.3. Occupational Health and Safety (OHS)......Page 253 24.4. Quality Management......Page 255 24.5. Facilities......Page 257 24.7. Deficient Repair Concepts......Page 258 24.8. Conclusion......Page 260 25.1. Introduction......Page 264 25.2. Aircraft Battle Damage Repair......Page 265 25.3. Comparison of Metallic Mechanically Fastened Repairs to Bonded Composite Repairs for ABDR......Page 268 25.4. Development of a Bonded Composite ABDR System......Page 274 25.5. Application of the DSTO/ABDR System......Page 279 25.6. Conclusions......Page 282 26.1. Introduction......Page 286 26.2. The Task at Hand - a Uniform Approach......Page 287 26.3. Current Approaches to Training and Certification......Page 288 26.4. Formalized Trade Structure......Page 289 26.5. The ARTI Model for Training of Bonded Repair Specialists......Page 290 26.6. Certification of Bonded Repair Specialists......Page 294 26.7. Conclusion......Page 298 27.1. Introduction......Page 300 27.2. Crack Location and Residual Strength......Page 301 27.3. Repair Substantiation Requirements......Page 303 27.4. Validation Strategy......Page 304 27.5. Design Validation (Finite Element Analysis)......Page 305 27.6. Cracked, Patched Model Including Thermal Effects......Page 306 27.7. Repair Substantiation (Representative Specimen Testing)......Page 308 27.9. Repair History......Page 312 27.10. Conclusion......Page 314 28.1. Introduction......Page 316 28.2. Fuselage Door Surround Structure Tests......Page 317 28.3. Fuselage Door Surround Structure Test Results......Page 322 28.4. Component Level Tests: Door Corner Specimen......Page 329 28.5. L-1011 Composite Doubler Installation......Page 335 28.6. FAA and Industry Approvals......Page 343 28.7. Conclusions......Page 344 29.1. Introduction......Page 348 29.2. Reinforcement Design......Page 349 29.3. Selection and Evaluation of Materials......Page 352 29.4. Selection and Evaluation of the Reinforcement......Page 353 29.5. Doubler Application Technology......Page 357 29.6. Doubler Fitment......Page 358 29.7. Fitment to Fleet Aircraft......Page 359 29.8. Conclusions......Page 360 30.1. Introduction......Page 362 30.2. FE Analysis of Bulkhead and Reinforcement......Page 363 30.4. Experimental Test Program......Page 367 30.5. Trial Installation of Reinforcement to Full-Scale Fatigue Test Article......Page 369 30.6. Discussion......Page 370 30.8. Acknowledgments......Page 372 31.1. Introduction......Page 374 31.2. Damage Tolerance Analysis......Page 375 31.3. Repair Options......Page 377 31.4. Design of the Bonded Repair......Page 378 31.5. FEM Model of the Patched Crack......Page 382 31.6. Conclusions......Page 386 32.2. Damage Tolerance Analysis......Page 388 32.3. Repair Options......Page 390 32.4. Design of the Bonded Repair......Page 392 32.6. Bonded Repairs......Page 395 References......Page 398 33.1. Introduction......Page 400 33.2. Load Cases......Page 401 33.3. Design and Stress Analysis......Page 402 33.4. Static Testing and Repair Validation......Page 406 33.5. Certification and Implementation to Aircraft......Page 408 33.6. Conclusions......Page 409 34.1. Introduction......Page 410 34.2. Design Studies......Page 411 34.3. Repairs to RAF Aircraft......Page 412 34.4. Repairs to EH101 Development Airframe Full Scale Fatigue Test Specimen......Page 416 34.5. Acknowledgements......Page 421 35.1. Introduction......Page 422 35.3. Repair Analysis......Page 424 35.4. Repair Design Validation......Page 429 35.5. Non-Destructive Inspection......Page 436 35.6. Current Status of DC-10/MD-11 Commercial Aircraft Repairs......Page 437 36.2. Background......Page 440 36.3. Repair Considerations......Page 443 36.5. Doubler Design and Analysis......Page 444 36.6. Doubler Manufacturing and Installation Procedures......Page 449 36.7. Doubler Fractographic Analysis......Page 452 36.8. Fleet Experience......Page 454 36.10. Conclusions......Page 457 36.11. Composite Repair Lessons Learned......Page 458 36.12. Acknowledgements......Page 459 Appendix A: Material Properties......Page 460 37.1. Introduction......Page 462 37.2. Demonstrator Doublers......Page 463 37.3. In-Service Environment and Repair Location......Page 465 37.4. Bond Durability and Surface Treatment......Page 467 37.5. Case Study Results......Page 468 37.6. Discussion and Lessons Learnt......Page 473 37.7. Conclusions......Page 475 38.2. Defect Description......Page 476 38.3. Justification of Approach......Page 477 38.5. Repair Procedure......Page 481 38.6. Continuing Airworthiness/Inspection......Page 482 39.1. Background......Page 486 39.2. Examples of Applicability to Large Areas......Page 487 39.3. Current State of the Technology......Page 488 39.4. Process Areas Requiring Adaptation......Page 490 39.5. Large Area Repairs in a Production Environment......Page 492 39.6. Conclusions......Page 497 40.1. Introduction......Page 500 40.2. Validation Testing......Page 502 40.3. Test Results......Page 504 40.4. Comparison between Test Results and Analytical Predictions......Page 508 40.6. Conclusions......Page 510 41.1. Background......Page 512 41.2. Repair Design......Page 515 41.3. Installation Development......Page 518 41.4. Industrialization and Repair......Page 519 41.5. Success and Failures......Page 520 41.6. Other Applications......Page 523 41.7. Cost Savings......Page 527 41.8. Additional Research......Page 528 41.9. Lessons Learned......Page 532 41.10. Summary......Page 535 42.1. Introduction......Page 538 42.2. Materials Development and Characterisation......Page 541 42.3. Installation of Composite Reinforcement......Page 545 42.4. Reinforcement Efficiency Assessment......Page 547 42.5. Service Performance......Page 549 42.6. Technology Improvement......Page 550 42.8. Conclusion......Page 551 42.9. Acknowledgement......Page 552 Index......Page 554 Back Cover......Page 570 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.