Consideration of the restriction of lateral contraction in the elastic behaviour of cohesive zone models

Cohesive zone models do not consider the lateral contraction of adhesive layers under tensile loads. The constraint of the lateral contraction by the adherents which depends on the geometry of the adhesive layer has a major influence on the normal stiffness of the joint. Two methods to improve the accuracy of the stiffness of cohesive zone models of rectangular adhesive layers are proposed in this paper. Both approaches use existing closed-form solutions for rectangular elastic layers between rigid plates. The first assigns an effective stiffness to the entire cohesive zone, the second approach defines a spatially varying stiffness to account for the difference in constraint of the adhesive close to the free surfaces and in the centre of the layer. The accuracy in joint stiffness for cohesive zone models gained by the two methods is tested in two extensive parametric studies considering both rigid and flexible adherents.