The deformation and fracture of composite materials with different coating thickness. Numerical simulation

The deformation and fracture of composite materials with different coating thickness are simulated. The boundary-value problem in a plane strain formulation is solved numerically by the finite-difference method. The mechanical response of a steel substrate and a boride coating is described by respective models for an elastic-plastic medium subjected to isotropic hardening and for elastic-brittle fracture. The coating-substrate interface geometry corresponds to the configuration found experimentally and is accounted for explicitly in the calculations. A series of numerical experiments was conducted for varying coating thickness. Within a thin surface layer (∼ 80 μm), the stress concentration near the interface is shown to increase as the coating thickness is decreased, i.e., as the interface approaches the free specimen surface. The effect is evident as early as the elastic deformation stage and is enhanced progressively as plastic deformation develops in the substrate.