Numerical Simulation of Steel Fiber Pull-Out Process Based on Cohesive Zone Model and Unified Phase-Field Theory

In steel fiber reinforced concrete, the interface is a very complex and weak structure. It is because of the weak interface layer between the steel fiber and the matrix that the reinforcing and toughening properties of the steel fiber cannot be fully exerted. The interface bond performance is the core of the meso-mechanical properties of steel fiber reinforced concrete. To study its influence on the mechanical properties of steel fiber reinforced concrete, three-phase finite element models of steel fiber pull-out are established based on the cohesive zone model and unified phase-field theory by means of FEM in this paper. The interface bond is simulated by a zero-thickness cohesive element, and the pull-out process of steel fiber in the concrete matrix is analyzed to provide a basis for the fracture research of steel fiber reinforced concrete. In this paper, the influence of factors such as the embedment depth, length–diameter ratio, embedment angle, and interface properties of steel fibers on the pull-out mechanical properties of steel fibers are considered, and the relevant finite element models are established to conduct numerical simulations of the pull-out process of steel fibers. The numerical simulation results are in good agreement with the experimental results, and this verifies the reliability of the model. The results show that the steel fiber pull-out finite element model established by the cohesive zone model and phase-field regularized cohesive zone model (PF-CZM) has a certain reliability; the peak pull-out load of the steel fiber increases with an increase in the embedment depth of the steel fiber, and decreases with an increase in the length–diameter ratio and embedment angle of the steel fiber; by controlling the strength of the interface layer and the concrete matrix, the reinforcement effect of the steel fiber on the concrete matrix can be improved; and the PF-CZM has a good characterization of the damage and failure evolution process of the concrete matrix.