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Abstract

This Thesis studies various aspects of the selection of adhesives for aircraft repairs. It was undertaken because of the need to repair a number of different aircraft types with a limited range of adhesives to minimise stockholdings and wastage of materials which have shelf-life limitations. The aspects studied were tensile strength, tensile modulus, elongation at failure, fracture energy, compression strength, compression modulus, water uptake, Tg dry and we t and diffusion coefficient. A computer programme written at Leicester Polytechnic was adapted to suit an IBM PC and this allowed water uptake within a lap joint to be related to time, diffusion coefficient and solubility coefficient.

Later in the project attempts were made to relate the tensile properties to lap joint strength. They were partially successful and led to a number of wedge tests to obtain fracture energy data. From this fracture toughness was calculated and this gave the best correlation with lap joint strength. It was finally concluded that good lap joint strength required an optimum combination of tensile strength, modulus, elongation to failure and fracture energy to achieve a fracture toughness of at least 3 MN.m-3/2

The fracture energy data clearly separated the brittle composite "matrix resins" from the tougher "adhesives" • It was concluded that matrix resins and adhesives can be more easily and effectively compared using the fundamental properties of the resins themselves than by using the limited data normally supplied by the Manufacturers on their data sheets.

It was also considered that the simpler tensile, compression and wedge tests used in this programme could obtain more data, more quickly and more cheaply than the thick adherend or napkin ring tests usually advocated.

From the results obtained it was possible to suggest specifications for both composite matrix resins and adhesives for making bonded metal or composite joints. These should lead to the development of better matrix resins and adhesives.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TA Engineering (General). Civil engineering (General) T Technology > TJ Mechanical engineering and machinery
Departments:	Doctoral Theses School of Science & Technology

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