Numerical Modeling of Quasi-Brittle Materials Using a Phase-Field Regularized Cohesive Zone Model with Optimal Softening Law

Abstract

In this paper, we propose an approach combining optimal softening laws and a phase-field regularized cohesive zone model (PF-CZM) for modeling the fracture and damage properties of quasi-brittle materials accurately. In this method, the optimal softening law is determined by comparing the predicted results with experimental data in the framework of the PF-CZM; three typical softening laws are considered. The PF-CZM with a length scale is used to model crack initiation and propagation without considering the mesh bias. We first investigate the mechanical responses and crack propagations of different concrete beams based on the above approach; the predicted results are compared with the data from conventional methods and experiments. The results indicate that the mechanical properties of concrete beams with the optimal softening law are better than the data reported in the literature. Further validation indicates that once the optimal softening law is determined, it is stable for the same group of materials. Moreover, we demonstrate that the PF-CZM can naturally predict and reproduce the critical notch offset and fracture transition process of three-point bending concrete beams and the fracture features of typical double-notched concrete beams, such as the interaction between two notches objectively, together with the changes of limit load capacity.

Keywords

• quasi-brittle materials
• phase field
• damage
• fracture
• crack propagation
• optimal softening law