On the evaluation of a critical distance approach for failure load prediction of adhesively bonded dissimilar materials

The validity of the critical longitudinal strain method (CLS) was proved for a wide range of adhesives and substrates employed in bonding similar substrates (same substrate thickness and material). However, the recent need of weight reduction yields a challenge of joining dissimilar materials, especially where composite laminates are bonded to metal substrates. Based on this industrial demand, the need of using a simple approach for failure load estimation of dissimilar adhesive joints is increasing. The aim of this work is to extend the CLS approach to be able to predict the failure load of adhesively bonded dissimilar single lap joints (SLJs). To achieve this, dissimilar SLJs with a brittle adhesive were manufactured and tested. On the other hand, experimental results of other researchers were also considered where composite substrates were bonded to metal adherends. Based on the results, it was found that by doing a minor modification, the already developed CLS method can be successfully applied to dissimilar SLJs. It is shown that the modified CLS method is able to predict the failure load of dissimilar SLJs with both brittle and ductile adhesives.