Theoretical investigation of the effect of plasticity on crack growth along a functionally graded region between dissimilar elastic–plastic solids

The influence of a functionally graded layer joining dissimilar elastic–plastic solids is studied in relation to interface crack growth. Conditions of small scale yielding are considered, and the boundary conditions applied on the outer edge of the region analysed are displacements for the elastic oscillating stress singularity fields corresponding to a sharp interface. A cohesive zone model is used to represent the fracture process, where the work of separation per unit area and the peak stress are basic parameters. Only crack growth on the initial crack plane parallel to the graded layer is analysed, but different locations of the crack plane relative to the layer are considered to obtain a parametric understanding. Crack growth resistance curves are illustrated, and the dependence of the steady-state fracture toughness on mode mixity is presented for several combinations of material parameters.