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 idealized straight crack front of a cracked generalized adhesive joint. The development is based on beam theory, the J-integral, and a beam-on-an-elastic-foundation model. Fracture experiments were performed with adhesively bonded split-cantilever-beam (SCB) specimens of different adherend widths and thickness ratios using two different adhesives, and it was seen that the fracture surface had a peculiar stepped arrowhead shape. The analysis and the experiments showed that both the energy release rate and the mode mix vary along the crack front of an SCB specimen, 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.