Predicting Debonding and Delamination in Adhesively Bonded T-joints

Different levels of FE modelling were conducted, in order to predict debonding and delamination in an adhesively bonded T-joint pull-off (T-pull) test. Specifically, 2D modelling was carried out to investigate the stress distribution in the T-pull specimen, so the locations where failures may potentially initiate could be identified, and the proper boundary conditions selected. 3D slice modelling was also conducted to predict failure propagation, to identify potential failure modes. The results indicate that the key failure mode is Mode I debonding at the deltoid. Furthermore, a half-width 3D T-pull model was set up to capture the failure mechanisms introduced by the free edges and the finite specimen width. The results indicate that Mode I debonding starts at the deltoid from the middle of the specimen, rather than from the free edges. This is due to the non-uniform stress distribution across the specimen width. The half-width 3D modelling result was compared with the 3D slice modelling result. The latter yields a slightly stiffer response due to more constraint, and a less conservative prediction because it assumes uniform stress distribution across the specimen width.