Prediction of fracture toughness of ceramic composites as function of microstructure: I. Numerical simulations

The evaluation of macroscopic material parameters such as fracture toughness as functions of microstructural attributes is a fundamental issue in material science. The task requires the quantification of both microstructure and material response. Currently, no systematic approach other than experiments exists for establishing microstructure–fracture toughness relations for materials. In this paper, we present a multi-scale computational framework based on the cohesive finite element method (CFEM) for predicting fracture toughness of materials as a function of microstructure. This framework provides a means for evaluating fracture toughness through explicit simulation of fracture processes in microstructures. The approach uses the J-integral, allowing fracture toughness to be calculated for microstructures with random heterogeneous phase distributions and fracture processes with arbitrary crack paths or micro-crack patterns. Calculations carried out concern two-phase Al2O3/TiB2 ceramic composites and focus on the effects of constitute behavior, phase morphology, phase distribution, phase size scale, and interphase bonding on fracture toughness. Results show that microstructure and constituent properties can significantly influence fracture behavior and combine to determine the overall fracture toughness through the activation of different fracture mechanisms. In particular, a combination of fine microstructure size scale, rounded reinforcement morphology, appropriately balanced interphase bonding strength and compliance can best promote desirable crack–reinforcement interactions and lead to enhanced fracture toughness.