THE STRESS INTENSITY FACTORS OF REGULARLY AND SINGULARLY PERTURBED-INTERFACE CRACKS

As we know, many composite failures occurring at interfaces, such as b etween thin-film and substrate or fiber and matrix, are mostly induced by the crucial far-field lateral stresses parallel to the interfaces. Among various mathematical models representing real cracks, the 'thin cut' model is of special interest, since it requires the simplest mat hematical methods in its study. This model, however, can not reflect s ome properties of real cracks. Especially, when the crack is uneven. I n this case, the far-field lateral stresses may dominate the fracture mechanism of uneven interface-cracks. But using the thin-cut mathemati cal analysis can just show zero stress intensifying phenomenon at the tips. The present paper adopted a modified mathematical model of an in terface crack with smoothly perturbed surface to study the different m echanism between the flat thin-cut and the perturbed-interface crack. The Hilbert's problem presented in this paper enables us to describe t he different perturbed-interface cracks. Via this representation the p erturbed-interface crack problem then can be solved in a unified manne r. A perturbation analysis technique based on the idea of Muskhelishvi li's potential formulation in conjunction with the homogeneous and gen eral Hilbert's problems to derive the solution is presented. The asymp totic solution for the title problem under the general uniform far-fie ld stresses is obtained for the first order of unevenness. When the fa r-field lateral stresses are much larger than the others, due to the a bove mentioned reasons, the corresponding solutions are most concerned and explicitly presented to analyze how the lateral stresses affect t he stress intensity factors as the crack face is uneven.