The effect of adherend thickness on the failure of adhesively-bonded single-lap joints

This paper presents an approach to predicting the failure and strength of joints bonded with a film-type adhesive (FM 73) using non-linear finite element method. First, lap-shear tests on Single-Lap Joints (SLJs) with different adherend thicknesses and overlap lengths were carried out and fracture surfaces of the SLJs were examined by scanning electron microscopy (SEM). Then, the stress analyses in the SLJs using a non-linear finite element method were performed by considering both the geometrical non-linearity and non-linear material behaviors of both adhesive and adherend (AA2024-T3), and Finite Element Analysis (FEA) results were compared with experimental results. Two different failure loci were seen when the failure surfaces of the SLJs were examined and both the stress analyses and experimental results showed that a catastrophic failure occured around the central zone of the overlap due to the effect of shear stresses, while the failure at the free edges of the adhesive layer originated from the peel stress in tension.