COATING CRACKS IN MATERIALS WITH GENERAL ANISOTROPY

The problem of a straight crack lying in the coating of a semi-infinite substrate is considered. The most general case of anisotropy is assumed for both materials (coating and substrate). The solution of Atkinson and Eftaxiopoulos [2] for a dislocation in an anisotropic bimaterial is modified to solve the fundamental problem of a dislocation in the coating, by including a corrective solution that accounts for the additional boundary conditions at the free surface. The coating crack is modelled as a continuous distribution of such dislocations. The resulting system of singular integral equations is solved by applying an inversion theorem and then using numerical integration. The stress intensity factors for modes I, II and III can be directly obtained from the dislocation densities. Numerical results are presented to compare the present analysis with existing solutions for some particular geometries and material models. For the general anisotropic case, results are presented showing the influence of a number of geometric and material parameters.