Phase-field modeling of brittle anisotropic fracture in polycrystalline materials under combined thermo-mechanical loadings

Phase-field modeling, owing to the regularized representation of discrete crack topologies, provides an efficient and robust framework for simulating complex fracture mechanisms in brittle materials. This study proposes an adaptive isogeometric-based approach to comprehend the fracture behaviour of polycrystalline materials under different thermo-mechanical loadings. The model considers anisotropy in the fracture resistance to examine intergranular and transgranular fracture mechanisms in polycrystalline materials. The individual grains in the morphology are modelled as anisotropic linear elastic domains possessing random preferential cleavage orientations. The present adaptive isogeometric framework uses polynomial splines over hierarchical T-meshes which offers an efficient adaptive mesh refinement scheme employing the phase-field parameter as an error indicator. Additionally, a hybrid-staggered scheme is implemented where the displacement field is computed using an isotropic model (no tension-compression splitting), while the phase-field parameter is evaluated based on an anisotropic model (with tension-compression splitting). The effect of thermo-mechanical coupling is examined on the fracture loads, and it is observed that the effects of temperature on the fracture loads are insignificant, however, it may accelerate or delay the fracture process. A series of numerical examples dealing with the fracture behaviour of single crystal, bicrystals, and polycrystalline domains are presented to showcase the robustness and capability of the present adaptive isogeometric framework.