Mixed-Mode Fracture Criterion in Alumina/Zirconia FGMs Using Finite Element Analysis

This study examines the mixed-mode fracture criterion for Alumina/Zirconia functionally graded materials (FGMs), based on the concept of the equivalent stress intensity factors K_eq. For this purpose, a computational algorithm is developed and incorporated into a finite element software, using a combination of five methods (FE method, Crack box technique CBT, Displacement extrapolation technique DET, Crack propagation criteria and Tanaka’s approach), in order to then determine the critical loading necessary to control the risk of crack propagation, as well as the determination of the different parameters (Stress intensity factors SIFs, bifurcation angle and T-stress). The mechanical properties of the Alumina/Zirconia FGM are supposed to change gradually through the cracked plate width, according to an exponential law (E-FGM). The continuous variation in material properties for Alumina/Zirconia FGMs is addressed by defining these properties at the centroid of each finite element. The proposed fracture criterion was identified according to the geometry of the specimen, the loading conditions and the mechanical properties of the FGM material. The frontier of crack propagation given by the proposed criterion is well defined and excellent results are obtained under pure mode-I and mixed-mode loadings.