Experimental investigation of the mixed-mode crack propagation in ZrO2/NiCr functionally graded materials

Mixed-mode fracture response of ZrO₂/NiCr functionally graded materials (FGMs) is investigated using fracture test, digital image correlation technique and extended finite element method. It is found that: (1) prior to crack initiation, the increasing elastic modulus ahead of crack-tip can enhance the mode mixity of crack-tip; (2) the crack with the increasing elastic modulus ahead of crack-tip kinks less than the one with the decreasing elastic modulus, which is caused by the elastic gradient and the local fracture toughness; (3) the heterogeneity of microstructure can cause the local perturbation but has no obvious effect on the overall crack propagation path.