Crack Propagation Path in Two-Directionally Graded Composites Subjected to Mixed-Mode I+II Loading

Crack propagation path in two-directionally graded composites was investigated by the finite element method. A graded extended finite element method (XFEM) was employed to calculate displacement and stress fields in cracked graded structures. And a post-processing subroutine of interaction energy integral was implemented to extract the mixed-mode stress intensity factors (SIFs). The maximum hoop stress (MHS) criterion was adopted to predict crack growth direction based on the assumption of local homogenization of asymptotic crack-tip fields in graded materials. Effects of material nonhomogeneous parameters on crack propagation paths were also discussed in detail. It is shown that the present method can provide relatively accurate predictions of crack paths in two-directionally graded composites. Crack propagates in the decreasing direction of effective Young's modulus. The shape and steepness of property gradient perpendicular to the crack surface have great influences on crack paths. Through redesigning material property reasonably, crack growth in graded material can be changed to improve mechanical behaviours of cracked structures. © 2017, Editorial Department of Transactions of NUAA. All right reserved.