Advances in the Bonded Composite Repair o f Metallic Aircraft Structure phần 2

Các vật liệu sửa chữa được lựa chọn cũng có thể được kiểm tra tiếp theo được yêu cầu và trong nhiều trường hợp sử dụng vật liệu tổng hợp của bo / epoxy là thuận lợi như các phương pháp dòng xoáy có thể được sử dụng để dễ dàng phát hiện các vết nứt bên dưới sửa chữa. | Chapter 2. Materials selection and engineering 23 If the problem causing the need for the repair was fatigue or corrosion it may be more appropriate to use a composite for the repair as these materials are effectively immune to these problems composite repair layups generally have fibre dominated properties which are immune to fatigue whereas layups with matrix dominated properties may be susceptible to fatigue . The repair material chosen can also be important where subsequent inspections are required and in many cases the use of boron epoxy composites is advantageous as eddy current methods can be used to readily detect the crack underneath the repair. This is usually more difficult if a metallic or graphite fibre patch is used due to the fact that these materials are electrically conducting. Metallic materials will require the use of stringent surface preparation and surface treatment processes to obtain a durable bond however if a corrosion inhibiting primer is used these processes could be conducted elsewhere and the patch stored prior to use. Composite repairs using thermosetting matrices such as epoxies are comparatively easier to prepare for bonding although the processes required are still important 2Ị. Thermoplastic composites are in general harder to bond to than the more commonly used thermoset composites. Finally metals lend themselves best to relatively flat repair locations due to the difficulty in accurately forming a metallic sheet to a curved profile. This is one of the strengths of composites where the desired shape can be formed into the repair during cure. Further considerations for the selection of a metallic material may include corrosion and patch thickness. To avoid galvanic corrosion problems between dissimilar metals a sensible choice would be to use the original material for the repair material as well. Where this is not possible a check should be made to ensure that different repair materials would not be susceptible to corrosion. For .

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88    611    2    20-07-2024
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