Simulation of cracks in a Cosserat medium using the extended finite element method

Cosserat (micropolar, asymmetric) elasticity can better predict the mechanical behavior of the materials with a characteristic length scale than the classical theory of elasticity. However, the area of fracture modelling in a Cosserat medium is not widely presented in the literature. The simulation of cracks in a Cosserat medium using the eXtended Finite Element Method (XFEM) is presented in this paper. The proper crack tip enrichment of the translational and microrotational fields is important for the robustness and efficiency of the XFEM/Cosserat model. Using the example of an edge crack of the Mode I in this paper, we have shown that the values of the J-integral for the Cosserat solid are higher than those for the equivalent classical elastic solid. The difference becomes significant for the cases of materials with strong micropolar properties. The dependence of the fracture behavior of the crack of different sizes on the Cosserat elastic constants was found to be significant. Therefore, it is recommended that the special tip enrichment is considered for the microrotational field, and a careful analysis of the material parameters is performed in order to model fracture in a Cosserat medium.