Eliminating Peel Stress in Adhesive Lap Joints

Abstract

Single lap adhesive joints are convenient and versatile ways to transmit tensile loads in bonded structures. It is well known that the adhesive in a lap joint experiences large peel stresses at the ends, which are implicated in bond failure (cohesive, adhesive and delaminating.) It is shown that peel stress is caused by the mismatch in elastic curvature of the adherends at the joint ends. Various simple geometrical modifications can reduce the curvature mismatch. In the first of two examples, symmetric, sloped, joggle style joint, the peak peel stress is reduced significantly in magnitude and changed from tensile to compressive. In the second one, consisting of a hook shaped and a straight adherend, the peel stress is virtually eliminated. The reduction, reversal, and elimination of peel stress have been motivated theoretically and demonstrated computationally.