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

TL;DR

This paper introduces a micromechanics-informed, direction-dependent phase field model for brittle fracture that accurately captures unilateral constraints and microstructural effects without artificial parameters.

Contribution

It develops a novel phase field model based on homogenization theory that incorporates microstructural behavior and unilateral constraints without ad hoc assumptions.

Findings

Accurately predicts crack paths in standard tests.

Provides stress-strain curves more precise than existing models.

Successfully models unilateral constraints in fracture simulations.

Abstract

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.