ISSN: 0884-6804
Page Count: 11

Fracture Load Predictions for Adhesive Joints Under Mixed Mode I-II-III Loading
Vintilescu, I
Graduate student and Professor, University of Toronto, ON

Spelt, JK
Graduate student and Professor, University of Toronto, ON

Abstract

Application of a method for predicting the fracture strength of adhesive joints under mixed mode I-II-III conditions is presented. The expressions used for the average energy release rate in Mode I, Mode II and Mode III along the idealized straight crack front of a cracked, generalized adhesive sandwich are based on a beam-on-elastic foundation model. Fracture experiments were performed with obliquely loaded unequal-adherend split-cantilever-beam (SCB) specimens of different widths and loading angles, using two different epoxy adhesives. The fracture strengths agreed reasonably well with predictions based on the previously measured fracture envelopes (Gc vs. mode ratio) obtained for these epoxies using equal-adherend obliquely loaded SCB specimens. It was seen that the fracture surface had an arrowhead shape for small loading angles (similar to that of SCB-type specimens), and a thumbnail shape for larger loading angles (similar to that of double-cantilever-beam (DCB)-type specimens). Moreover, a sharp step was observed in the thickness of the residual adhesive half-way across the specimen width. As in the case of equal-adherend specimens, the addition of Mode I greatly reduced GC, and caused the effect on GC of Mode II to be similar to that of Mode III.

Keywords:
fracture, adhesive joints, mixed-mode, Mode I, Mode II, Mode III, energy release rate, split cantilever beam

Paper ID: CTR10851J
DOI: 10.1520/CTR10851J
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