Modeling cracks in viscoelastic materials at finite strains

Viscosity is a manifestation of internal friction in materials. Such friction is accompanied by the dissipation of energy, which affects deformation and fracture. In the present work, we develop a new theoretical formulation and its numerical implementation for modeling fracture in viscoelastic soft materials. Concerning the theory, we extend the material-sink approach by including a viscosity description at finite strains. Concerning numerical methods, we introduce a mixed finite-element formulation based on the relative deformation gradient and implement it in Abaqus. Representative numerical examples show that the proposed approach captures the viscous behavior of material and demonstrates the coupling between viscosity and fracture. Simulations reveal that the viscous dissipation suppresses minor crack branching as compared to the purely hyperelastic case, when the strain rate is relatively small. That said, when the strain rate is relatively large, viscoelastic and hyperelastic materials fracture consonantly.