MIXED-MODE FRACTURE CHARACTERIZATION OF ADHESIVE JOINTS

A novel load jig is presented which allows mixed-mode fracture testing of adhesive joints and composite laminates over the entire range from mode I to mode II, by using a single equal adherend double-cantilever -beam specimen. Experiments performed with the load jig showed that G( IIC) was approximately three times higher than G(IC) for the tested ad hesive system consisting of FPL-etched 7075-T6 aluminium adherends bon ded with Cybond 4523GB (American Cyanamid) epoxy adhesive. Experimenta l data showed that G(C) was independent of crack length and that there was no dependence of G(IC) on adherend thickness. Comparison of G(IIC ) values obtained by using the load jig to test conventional end notch flexure (ENF) specimens indicated that there are relatively small fri ction effects between crack faces in mode II testing of ENF specimens. The experimental data were also used to evaluate three different anal ytical techniques for the mode partitioning of unequal adherend specim ens.