A micromechanics-informed phase field model for brittle fracture accounting for unilateral constraint

We propose a new direction-dependent model for the unilateral constraint involved in the phase field approach to fracture and also in the continuous damage mechanics models. The construction of this phase field model is informed by micromechanical modeling through the homogenization theory, where the representative volume element (RVE) has a planar crack in the center. The proposed model is made closely match the response of the RVE, including the frictionless self-contact condition. This homogenization approach allows to identify a direction-dependent phase field model with the tension-compression split obtained from cracked microstructures. One important feature of the proposed model is that unlike most other models, the material degradation is consistently determined without artificial assumptions or ad hoc parameters with no physical interpretation, thus, a more realistic modeling is resulted. With standard tests such as uniaxial loadings, three-point bending, simple shear, and through-crack tests, the proposed model predicts reasonable crack paths. Moreover, with the RVE response as a benchmark, the proposed model gives rise to an accurate stress-strain curve under shear loads, more accurate than most existing models.

Automated summary

A new direction-dependent model is proposed for handling the unilateral constraint in the phase field approach to fracture and continuous damage mechanics models. The model is constructed based on micromechanical modeling and homogenization theory, closely matching the response of the representative volume element (RVE) and allowing for accurate predictions of crack paths and stress-strain curves. This approach results in more realistic modeling without artificial assumptions or parameters, with the model showing improved accuracy compared to existing models in predicting stress-strain behavior under shear loads.