Strength Prediction of Adhesively Bonded Single Lap Joints with the eXtended Finite Element Method

Abstract

Because of the planar load introduction, its high strength over weight ratio, the avoidance of holes, corrosion resistance and component reduction, adhesively bonded joints attract increasing attention in the field of lightweight construction. Nonetheless, a reliable prediction of the joints’ behaviour in terms of stress and strength is still a tremendous challenge. In this study the eXtended Finite Element Method (XFEM) in combination with cohesive behaviour is used to model crack growth under quasi-static loading. The objective of this work is to study the influence of different continuum mechanical material models for the adhesive like the von Mises, linear and exponent Drucker-Prager model on XFEM strength predictions. It will be evaluated whether the strength prediction of joints mainly loaded in shear is more accurate with a high sophisticated material model. Therefore, strength predictions of Single Lap Joints (SLJ) with thick aluminium adherends according to ASTM D 5656 are performed. With the help of this example, the chosen continuum mechanics material models for the film adhesive are compared. The material parameters for the adhesive are derived from a number of specimen types with different load combinations. Herein, digital image correlation (DIC) data recorded during experimental tests are used to assess the material models in combination with the derived material parameters. Furthermore, with the experimental results the performed strength predictions are evaluated. In addition, a mesh convergence study for the adhesive bondline with regard to the predicted strength is carried out. It could be revealed that XFEM in combination with a suitable yield criterion and appropriate material parameters is a valid technique for the strength prediction of lap shear joints since the variance to the experiments is less than 1 %.