3D Cohesive Investigation on Branching for Brittle Materials

The experiments on dynamic crack propagation in PMMA (polymethyl methacrylate) and in soda lime glass conducted by Fineberg and Sharon (see [1-2] and quoted references) during the last decade pointed out some characteristic features of the microbranching instability in brittle materials. They observed the existence of a critical velocity for the onset of the microbranching; described the relation between the form and orientation of microcracks growth and the specimen external surface roughness; and analyzed the effects of the 3D-to-2D transition. Fineberg and Sharon’s results opened a new perspective to the interpretation of fracture processes and have raised a considerable interest in the scientific community for fracture dynamics of brittle materials. We aim to reproduce the features of branching instabilities experimentally observed in brittle materials by using the cohesive theories of fracture and finite element discretization. We explicitly simulate the propagation of unstable fracture in prenotched thin plates, loaded in pure mode I. The analyses have been carried out for two different brittle polymeric materials, i. e. PMMA and Homalite-100. Our simulations reproduced with a considerable fidelity the main features observed in Fineberg and Sharon’s experiments.