Numerical modeling of compressive failure mechanisms in ceramic materials at high strain rates

We present a three-dimensional micromechanical computational framework for the direct mesoscale simulation of compressive failure mechanisms in ceramic materials at high strain rates based on the Optimal Transportation Meshfree (OTM) method and the microstructure-informed Eigen-fracture approach. A statistically equivalent polycrystal structure of ceramics is reconstructed to match the probability distribution functions of the grain size, orientation and grain boundary misorientation measured in experiments. The crystal elasticity model with damage is employed to predict the anisotropic dynamic response of the polycrystalline structure. Interaction between the crack front and the microstructure during the dynamic failure process is indicated in the model by considering the equivalent energy release rate as a function of the local micro-features. The computational model is validated by directly comparing the predicted compressive strength of 6H-SiC at various strain rates against Split-Hopkinson pressure bar (SHPB) experiments. Influence of the microstructure on the dynamic compressive failure mechanisms of 6H-SiC, including the effects of porosity and void spatial distribution as well as the strain-rate dependence, is quantified thoroughly by using the proposed computational scheme. The analysis demonstrates that the ultimate macroscopic compressive strength of ceramic materials is determined by the competition and combination of intergranular and transgranular fractures in the microstructure.