EXPERIMENTAL-DETERMINATION OF SILICA COPPER INTERFACIAL TOUGHNESS

Experiments designed to measure the fracture toughness of ceramic meta l interfaces over a wide range of phase angles are described, and a si mple approach to data analysis accounting for plasticity effects in sp ecifying interfacial toughness is outlined. A modified version of a fi xture proposed by Richard and Benitz [Int. J. Fract. 22, R55 (1983)] i s used to apply mixed-mode loadings to silica/copper sandwich specimen s. The experimentally observed crack trajectories depend on the phase angle of loading. In general, the tendency for initial propagation of the crack to occur in the ceramic increases as the magnitude of the ph ase angle increases. The introduction of a modest amount of mixed-mode loading resulted in a substantial increase in fracture toughness, fro m approximately 2.2 J/m2 at 3-degrees to 6.4 J/m2 at 16-degrees and 8. 7 J/m2 at - 10-degrees. The data clearly indicate that plasticity effe cts become increasingly important as the magnitude of the phase angle increases.