DEFLECTION AND PENETRATION OF CRACKS AT AN INTERFACE BETWEEN 2 DISSIMILAR MATERIALS

The tendency of a crack to deflect or penetrate at an interface betwee n two dissimilar elastic materials in a finite-sized sample is investi gated with the boundary element method. The ratio of the energy releas e rate of a deflecting crack to the maximum energy release rate of a p enetrating crack is computed as a function of the Dundurs' elastic mis match parameters for several double-edged notch specimen geometries an d loading conditions. Over the entire range of material parameters, th e results displayed only a weak dependence on the loading conditions i mposed on the specimen, the aspect ratio of the specimen, and on Dundu rs' parameter, beta. For moderate differences in the relative stiffnes ses of the two materials and when the crack is advancing toward a stif fer material, we find essentially no difference between the singly and doubly deflected crack, and the numerical calculations are in excelle nt agreement with recent analytical predictions [1]. However, when the crack is advancing into a material of much lower modulus, the numeric al calculations for a doubly deflected crack are smaller than the anal ytical predictions.