Stress intensity factors for four interface-close cracks between a nonhomogeneous bonding layer and one of two dissimilar elastic half-planes

•Four interface cracks are placed in a layer bonding two dissimilar elastic half-planes.•The conventional stress intensity factors which are physically acceptable are estimated for four interface cracks.•The stress intensity factors obtained are useful in fracture mechanics from an engineering view point.

Stress intensity factors are estimated for four collinear interface cracks that are situated at the interface between a nonhomogeneous elastic bonding layer and one of two dissimilar elastic half-planes. Tensile stress is applied normal to the cracks. The material properties of the bonding layer vary continuously from those of the lower half-plane to those of the upper half-plane. To solve this problem, two solutions are combined: the solution for two inner collinear cracks and the solution for two outer collinear cracks. To satisfy the boundary conditions for the combined solution, the differences in the crack surface displacements are expanded as a series of functions that are zero outside the cracks. The unknown coefficients in the series are solved using the Schmidt method so they satisfy the conditions inside the four cracks. The stress intensity factors are calculated numerically for the selected crack configurations.