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The conventional approach to through-life-support for aircraft structures can be divided into the following phases: (i) detection of defects, (ii) diagnosis of their nature and significance, (iii) forecasting future behaviour-prognosis, and (iv) pre scription and implementation of remedial measures including repairs. Considerable scientific effort has been devoted to developing the science and technology base for the first three phases. Of particular note is the development of fracture mechanics as a major analytical tool for metals, for predicting residual strength in the presence of cracks ( damage tolerance) and rate of crack propagation under service loading. Intensive effort is currently being devoted to developing similar approaches for fibre composite structures, particularly to assess damage tolerance and durability in the presence of delamination damage. Until recently there has been no major attempt to develop a science and tech nology base for the last phase, particularly with respect to the development of repairs. Approaches are required which will allow assessment of the type and magnitude of defects amenable to repair and the influence of the repair on the stress intensity factor (or some related parameter). Approaches are also required for the development and design of optimum repairs and for assessment of their durability.
Inhaltsverzeichnis
1. Introductory chapter.- 1.1 Bonded vs bolted repairs.- 1.2 Combined bonded/bolted repairs.- 1.3 Adhesives.- 1.4 Adhesive testing.- 1.5 Surface preparation.- 1.6 Environmental behaviour.- 1.7 Summary.- 2. Surface treatments for bonded repairs of metallic components.- 2.1 Introduction.- 2.2 Background.- 2.3 Structural aluminium alloys.- 2.4 Phosphoric acid anodizing.- 2.5 Chromic acid anodizing.- 2.6 Titanium alloys.- 2.7 Summary.- 3. Design and analysis of bonded repairs for metal aircraft structures.- 3.1 Introduction.- 3.2 Design of adhesive bonded repairs in thin sheet metal construction.- 3.3 Residual strength of flawed or damaged bonded joints.- 3.4 Acceptance criteria for bonded flaws and damage.- 3.5 The pitfalls of life prediction for adhesive-bonded joints.- 3.6 Surface preparation for adhesive bonded repair of metal structure.- 3.7 Conclusions.- 4. Crack patching: design aspects.- 4.1 Introduction.- 4.2 The finite element formulation.- 4.3 Repair of cracks in Mirage III lower wing skin - a design study.- 4.4 Neutral axis offset effects.- 4.5 Initial design procedures.- 4.6 Comparison with experimental and 3-D results.- 4.7 Repair of semi elliptical surface flaws.- 4.8 Repair of cracked holes.- 4.9 Repair of cracked fastener holes.- Appendix A.- 5. Theoretical analysis of crack patching.- 5.1 Introduction.- 5.2 Formulation and notation.- 5.3 Load transfer to bonded reinforcements.- 5.4 Two stage analytical solution.- 5.5 Residual thermal stress due to adhesive curing.- 5.6 Bending effects.- 5.7 Partial reinforcement.- 5.8 Conclusion.- 6. Crack patching: experimental studies, practical applications.- 6.1 Introduction.- 6.2 Adhesive system and process selection.- 6.3 Thermal and residual stress problems.- 6.4 Design correlations and materials allowables.- 6.5A preliminary design approach.- 6.6 Crack propagation behaviour.- 6.7 Applications of crack patching.- 7. Repair of composite aircraft.- 7.1 Introduction.- 7.2 Composite fabrication.- 7.3 Defects.- 7.4 Repair materials.- 7.5 Bonded repair - composite repair concepts.- 7.6 Effect of moisture on bonded repairs of composites.- 7.7 Design of bonded repairs.- 7.8 Composite service damage experience.- 7.9 Specific component repair.- 7.10 Future requirements.
