MIXED-MODE-II MIXED-MODE-III FRACTURE OF ADHESIVE JOINTS

This paper presents approximate closed-form expressions for the local energy release rate in Mode I, Mode II, and Mode III along the idealiz ed straight crack front of a cracked generalized adhesive joint. The d evelopment is based on beam theory, the J-integral, and a beam-on-an-e lastic-foundation model. Fracture experiments were performed with adhe sively bonded split-cantilever-beam (SCB) specimens of different adher end widths and thickness ratios using two different adhesives, and it was seen that the fracture surface had a peculiar stepped arrowhead sh ape. The analysis and the experiments showed that both the energy rele ase rate and the mode mix vary along the crack front of an SCB specime n, making it unsuitable for the determination of fundamental fracture properties. However, the SCB specimen provided a useful means to test an engineering approach to predict the out-of-plane fracture loads of adhesive joints.