Selection of adhesives and pretreatments for specific failure types in adhesively bonded joints

To accurately predict failure of adhesively bonded joints, it is necessary to distinguish between the different failure modes and failure criteria that can occur. In order to do so and to verify theoretical results with experimental results, joints must be available that exhibit these different failure modes. Therefore, a test programme has been set up to select adhesive systems (i.e. the combination of adherends, surface pre-treatment and adhesive), which result in reproducible cohesive and/or adhesive failure before and after ageing. The test results, the encountered fracture surfaces and the selected adhesive systems are discussed in this paper. In addition to the classical distinction between cohesive and adhesive failure, it was found necessary to divide the cohesive fracture patterns into a) centreline cohesive !allure and b) "cohesive failure near the interface". This division can be explained by the differences in stress over the bondline thickness and the type of adhesives that were used