A new model for fracture analysis of functionally graded coatings under plane deformation

A new multi-layered model for fracture analysis of functionally graded materials (FGMs) with arbitrarily varying Young's modulus and Poisson's ratio under plane stress-state deformation has been developed. In this model, the FGM is divided into several sub-layers and in each sub-layer both Young's modulus and Poisson's ratio are assumed to be a linear function of the depth and are continuous on the sub-interfaces. With this new model, an interface crack problem of a functionally graded coating bonded to a homogeneous half-plane under normal and shear loading is investigated. Employment of transfer matrix method and Fourier integral transform technique reduces the problem to a system of Cauchy singular integral equations which are solved numerically. Stress intensity factors (SIFs) of an interface crack are obtained for various forms of Young's modulus and Poisson's ratio. The results reveal that the present model is very efficient and that the form of the Young's modulus influences the SIFs much.