FRACTURE ALONG AN INTERLAYER

A nonhomogeneous interlayer is introduced between two dissimilar mater ials to characterize the transition of the elastic moduli across the b imaterial interface. The 1/square-root r singularity field near the ti p of an advancing interlayer crack is related to the remote interface crack tip field for general aligned orthotropic bimaterials. An approx imate but explicit relation for the phase shift between the near the t ip and the remote singularity fields is derived. Comparisons with anal ytical and numerical solutions show that the relation is fairly accura te. The interlayer model provides insightful interpretations of severa l important concepts of interface fracture mechanics, such as stress o scillation, near tip contact and mode mixity. For crack tip mode mixit y. psi(tip), in the range - pi/2 < psi(tip) < pi/2, the crack tip is t ruly open. The crack is partially closed for psi(tip) = +/- pi/2. Plas ticity effects associated with dislocation emissions from the crack ti p are also considered.