Spall strength of symmetric tilt grain boundaries in 6H silicon carbide

Characterizing microstructural effects on the dynamical response of materials is challenging due to the extreme conditions and the short timescales involved. For example, little is known about how grain boundary characteristics affect spall strength. This study explores 6H-SiC bicrystals under shock waves via large-scale molecular dynamics simulations. We focused on symmetric tilt grain boundaries with a wide range of misorientations and found that spall strength and dynamical fracture surface energy are strongly affected by the grain boundary microstructure, especially the excess free volume. Grain boundary energy also plays a considerable role. As expected, low-angle grain boundaries tend to have higher spallation strengths. We also extracted cohesive models for the dynamical strength of bulk systems and grain boundaries that can be used in continuum simulations.