Experimentally measuring weak fracture toughness anisotropy in graphene

Extended finite element analysis (XFEM) modeling the fracture process of 2D materials with anisotropic fracture toughness. Modification from the classic XFEM, this updated script is based on the maximum energy release rate criterion, and anisotropic fracture toughness in sine form and hexagonal symmetry is included. By modifying the ratio of maximum and minimum fracture toughness, model geometry, boundary conditions, and pre-crack location and direction, the fracture patterns, as well as the local fracture parameters including stress intensity factors and energy release rate at the crack tip can be calculated. Moreover, in this script, the distance of the crack extension at every step is irrelevant to the mesh size of the geometry, thus accuracy and computation efficiency is enhanced.