Fracture Modeling of Viscoelastic Behavior of Solid Propellants Based on Accelerated Phase-Field Model

Viscoelastic solids, such as composite propellants, exhibit significant time and rate dependencies, and their fracture processes display high levels of nonlinearity. However, the correlation between crack propagation and viscoelastic energy dissipation in these materials remains unclear. Therefore, accurately modeling and understanding of their fracture behavior is crucial for relevant engineering applications. This study proposes a novel viscoelastic phase-field model. In the numerical implementation, the adopted adaptive time-stepping iterative strategy effectively accelerates the coupling iteration efficiency between the phase-field and the displacement field. Moreover, all unknown parameters in the model, including the form of the phase-field degradation function, are identified through fitting against experimental data. Based on an introduced scaling factor, the mechanical response behaviors of solid propellant dogbone specimens under cyclic loading, relaxation, and tension are analyzed, and the predictive capacity of the model is demonstrated by comparing the experimental data with the simulation results. Finally, modeling results for Mode-I and Mode-II crack propagation in single-edge-notched specimens indicate that the reduction of viscous energy dissipation will significantly increase the fracture growth rate, but under the same boundary conditions, the crack path remains unchanged.