On fracture criteria in phase field model for fracture in asphalt concrete

Extensive research has explored cracking in asphalt mixtures under pure mode-I conditions; however, heavy traffic loads often lead to crack formation under mixed-mode fracture conditions in asphalt pavements. This paper presents a phase field damage model to simulate mixed-mode I-II fracture phenomena observed in asphalt concrete. In contrast to the conventional approach employing cohesive zone models, which restrict crack propagation exclusively to the peripheries of interface elements within the computational mesh, the model presented herein can simulate crack evolution throughout the material domain. Crack inception and material degradation were modeled using a unified failure model and a modified G-criterion. Mode I and mixed-mode I-II asphalt fracture experiments reported in the literature are replicated using the phase field model. The results show that the model can effectively simulate the fracture response with sufficient accuracy. The effect of the offset ratio on the peak load, dissipation energy, mode-mixity and mode of failure is studied. In addition, the fracture response under different failure criteria is simulated using the parameter χ. It is concluded that with an increase in notch offset, the peak load, dissipated energy, and mode-mixity increase. Furthermore, it is demonstrated that in the case of the provided notched beam with a mere 23% mode II contribution, the modified and tensile failure criterion based PFMs are equivalent for χ≥0.707.