摘要
The asymmetric tip morphology of a creep microcrack propagating along a bimaterial interface is presented based on the assumptions that the near-tip shapes are developed from surface diffusion controlled crack growth and that a steady state prevails. Following Chuang and Rice, a single master curve still can adequately describe the near-tip shapes to within 6% accuracy, but four cases of crack-tip morphology emerge depending on the ratios of surface to interfacial free energy and diffusivity of the adjoining phases. For fixed ratios of the two surface diffusivities, crack tip morphology maps in the space of specific surface energies are constructed with which areas associated with each individual case are indicated. Predicted cases on a set of bimaterial systems are tabulated and discussed. TEM photos of creep crack tips in alumina and silicon nitride are presented for illustration. The information given here is essential to a coupled analysis of diffusion and elastic deformation at a composite interface which may ultimately yield predictions of the delamination rate between the reinforcing phase and the matrix phase as a function of applied stress, temperature and other relevant materials' constants. © 1992.