An improved ordinary state-based peridynamic model for cohesive crack growth in quasi-brittle materials

Ordinary state-based peridynamics (OSBPD) is a well-established peridynamic (PD) model, but its applications are restricted in brittle fracture because the failure models proposed in OSBPD are mainly to describe brittle fracture rather than quasi-brittle fracture. This work attempts to propose a damage model to overcome this limitation for the investigation of damage and crack propagation in quasi-brittle materials. To this aim, a PD version of the cohesive zone model (CZM) is established in OSBPD for the fracture analysis of quasi-brittle materials. A degradation curve is proposed in the damage model to represent the cohesive effect in fracture process zone (FPZ), which is similar to the tension softening curve in CZM. The damage model can be uniquely determined once the tensile strength, the elastic modulus, the specific fracture energy, and tension softening constitutive law are given. Moreover, several representative examples of mode-I and mixed mode concrete fractures are simulated using OSBPD to validate the proposed damage model. The predicted load-displacement curves and crack paths in all the cases are in good agreement with the experimental results or other numerical results. In addition, a reloading approach is proposed to obtain the descending part of load-displacement curve when the load-controlled loading procedure is adopted.