Modelling Stepped-Lap Adhesive Joints by the Extended Finite Element Method

For the joint strength prediction of bonded joints, Fracture Mechanics-based techniques are often used. In this context, the tensile ( GIC) and shear toughness ( GIIC) are two of the most important parameters to predict the joint behaviour. The Finite Element Method ( FEM) has been used for strength prediction in the last decades. Cohesive zone modelling ( CZM) coupled to a FEM analysis is generally accepted as an accurate method. More recently, the Extended Finite Element Method ( XFEM) has emerged. This work aims to validate the XFEM to predict the behaviour of stepped-lap joints with different overlap lengths ( LO). Three adhesives, Araldite (R) AV138, Araldite (R) 2015 and Sikaforce (R) 7752, whose properties are quite different, were used in the analysis. For the XFEM strength prediction, different damage initiation criteria were used using either stresses or strains. The XFEM was found to be adequate to predict the joint strength using the Quadratic Stress ( QUADS) and Maximum Stress ( MAXS) damage initiation criteria.