Supershear rupture with a two-scale damage model

Abstract

An investigation of intersonic rupture is performed in a two-scale framework, with a damage model obtained by homogenization from microstructures with dynamically evolving mode II microcracks. The macroscopic fracture is analyzed in connection with the microcrack propagation. It is found that the supershear transition and the subsequent intersonic failure are achieved by collective effects of propagation and coalescence of sub-Rayleigh microcracks ahead the macroscopic rupture front. This is similar to the behavior experimentally observed for mode I dynamic brittle fracture (Guerra et al. 2012). Numerical simulations of a pre-cracked plate under shear loading are performed and characteristic features like the formation of shear shock waves, the mother-daughter or direct transition mechanisms, the specific evolutions of the rupture speed or the symmetry breaking near the crack tip are retrieved. Parametric studies allow to determine the influence of the size of the microstructure, the applied loading and the fracture properties of the solid. For the asymmetric impact of a Homalite plate problem (Rosakis et al., 1999), the numerical results obtained with the damage model are successfully confronted with the experimental observations.