A phase field model of crack propagation in anisotropic brittle materials with preferred fracture planes

Abstract

In this work, a phase field fracture model is proposed that includes single crystal anisotropy in both the elastic constants and the fracture energy. The strain energy is decomposed into tensile and compressive parts, and only the tensile part contributes to crack propagation. Anisotropic fracture energy is included to capture the impact of crystal orientations on crack paths. The performance of our model is demonstrated using simulations of single edge notched tension specimens with four different microstructures. Firstly, crack propagation is predicted in single crystal specimens with anisotropic fracture energy but isotropic elastic constants to investigate the impact of the anisotropy strength parameter and the crystal orientation. The anisotropy strength impacts the crack angle and the maximum stress experienced before fracture. The crystal orientation impacts the crack angle but not the maximum stress. Next, similar single crystal simulations are carried out with both anisotropic fracture energy and anisotropic elastic constants, and the crystal orientation impacts the crack direction, the initial slope of the stress strain curve, and the maximum stress before fracture. The capabilities of the model are demonstrated in bicrystal and polycrystal geometries, with cracks changing direction as they cross grain boundaries.