THE INTERFACE CRACK PROBLEM FOR A NONHOMOGENEOUS COATING BONDED TO A HOMOGENEOUS SUBSTRATE

The debonding problem for a composite layer that consists of a homogen eous substrate and a nonhomogeneous coating is considered. It is assum ed that the problem is one of plane strain or generalized plane stress and the elastic medium contains a crack along the interface. It is fu rther assumed that the thermomechanical properties of the medium are c ontinuous functions of the thickness coordinate with discontinuous der ivatives and the kink line of the property distributions corresponds t o the ''interface''. The mixed-mode crack problem is formulated for ar bitrary crack surface tractions and sample results are given for unifo rm normal and shear tractions. The main variables in the problem are t wo dimensionless length parameters and a nonhmogeneity constant. Calcu lated results consist of primarily the stress intensity factors and th e strain energy release rate and are partly intended to provide benchm ark solutions for further numerical studies.