The stress intensity factors of regularly perturbed-interface cracks of anisotropic bimaterials

Based on Lekhnitskii-Eshelby-Stroh (LES) representation and perturbation analysis, analytic solutions are given for displacement and stress fields of two anisotropic half-planes, forming a composite bimaterial, with a perturbed-interface crack. Among various mathematical models representing real cracks, the ''thin cut'' model is of special interest, since it requires the simplest mathematical methods in its study. However, the model does not reflect some of the properties of actual cracks, in particular the crack should be uneven. When the lateral stresses, parallel to the interface, dominate in the fracture mechanism, the thin-cut model cannot reveal any stress intensifying phenomenon, while many failures, occurring in the interfaces of thin-film and substrate or fiber and matrix, are always induced by crucial lateral stresses. For these reasons, the unevenness effect of crack faces must be taken into account to determine the practical stress intensity factors for predicting the interface fracture behavior. A modified crack with smoothly perturbed surfaces ensures good agreement with reality, while retaining the simplicity of the mathematical model. Mathematically, we consider the elastic problem of a perturbed-interface crack lying along the interface of two bonded dissimilar anisotropic half-planes and the uniform far-field stresses are specified. When the lateral stresses are much larger than others, the solutions are determined to the first-order of unevenness to understand how the lateral stresses affect the stress intensity factors as the crack face is uneven. (C) 1997 Elsevier Science Ltd.