Dual Role for Heterogeneity in Dynamic Fracture

Are heterogeneous materials harder to break than homogeneous ones? Predicting rapid crack propagation in the presence of inhomogeneities remains a challenge. Linear perturbations leave the net speed of fracture unchanged. We obtain a nonlinear equation of motion for planar crack fronts to gain insight into the dynamic fracture of moderately heterogeneous solids. The coupling of the front geometry to the heterogeneity landscape renormalizes the energy dissipation and the crack velocity. In materials whose toughness is weakly sensitive to crack speed, such as silica glass, heterogeneity results in increased dissipation and slower crack propagation. However, heterogeneity has a reduced effect and may even facilitate fracture in strongly velocity-dependent materials.