An investigation on the strength of single lap adhesive joints with a wide range of materials and dimensions using a critical distance approach

Several criteria have been proposed for failure load prediction of adhesively bonded single lap joints (SLJs). However, the presence of factors such as the bimaterial interface, the ductility or brittleness of adhesives and also the singularity at the bonding ends make the failure prediction of SLJs a challenging issue. Recently a distance based failure load prediction method named CLS (critical longitudinal strain) was applied successfully on SLJs with different bonding lengths. This method uses a specific distance and the critical longitudinal strain as failure parameters. In this paper, the CLS was used on a variety of SLJs with a wide range of materials and geometries. Five types of adhesives including epoxies, silicones, bismaleimides, polyurethanes and acrylic were considered and the substrates consisted of different steels and aluminum alloys. The results show that the CLS can predict the failure load of SLJs with different adhesives including ductile and also brittle adhesives very well. Also, there is a good correlation between the predictions and the experimental data for SLJs with different dimensions. It was also found that the critical longitudinal strain is a function of the substrate thickness and also the Young's modulli of the substrate and adhesive. A relation was proposed for the prediction of the critical longitudinal strain in SLJs with different configurations.