Stress intensity factor in bonded joints: influence of the geometry

This paper explores the effects of the main geometrical features of an adhesive single lap joint (subjected to tensile stress) on the singular stress field near to the interface end. First, an analysis on a bi-material block is carried out, to evaluate the accuracy obtainable from finite element modelling by comparison with the analytical solution for the singularity given by the Bogy determinant. Then, the study on the lap joint is carried out, by varying both macroscopic (bond length, thickness) and local (edge shape and angle) parameters, for a total of 30 cases. The great importance of the angle to reduce the singular stresses is confirmed, whilst the edge shape plays a lesser role. The bond length has the effect of increasing or decreasing the stress values and the stress intensity factor, and the adhesive thickness has a relevant effect only in case of square edge. Finally, the problem of the significance of the stress intensity factor, representative of the stress distribution only for a given edge angle, is recalled.