Substrate Thickness Optimization in Multi-material Single Lap Adhesive Joints

Adhesive bonding of dissimilar materials introduces stress concentrations due to stiffness mismatch between the substrates, thereby exacerbating the peel and shear stresses leading to premature failures in single lap configurations. This work demonstrates that the stress distribution can be improved by decreasing the thickness of the stiffer substrate; and presents a structured approach to find the optimum thickness to improve overall joint performance. First, the critical stress components and critical locations in the single lap joint were identified for each mode of failure. Then, a minimax type optimization framework was developed using severity-weighted parameters for each critical stress component. Optimal thickness obtained from the proposed framework agreed with FEA based parametric studies within 10% variation. Overall, this approach can generate design charts and aid in efficient designs for multi-material joining.