Numerical and experimental investigation of mixed-mode fracture parameters on silicon nitride using the Brazilian disc test

Engineering applications of ceramics can often involve mixed-mode conditions involving both tensile and shear loading. Mixed-mode fracture toughness parameters are evaluated for applicability to ceramics using the Brazilian disc test on silicon nitride. Semi-elliptical centrally located surface flaws are induced on the disc specimens using Vickers indentation and compression loaded to fracture with varying levels of mode mixity. The disc specimens are modelled via 3D finite element analysis and all three modes of stress intensity factors computed along the crack front, at failure load. We present a numerical and experimental investigation of four widely used mixed-mode fracture criteria and conclude that the critical strain energy release rate criterion is simple to implement and effective for silicon nitride under mixed-mode conditions.