Rate-dependent fracture of transient networks

Soft viscoelastic polymers and gels are commonly used a wide range of applications owing to their softness and the ability to accommodate large deformations. Their applicability is however often limited by their tendency to fracture in ways that are cannot be predicted by conventional elastic fracture mechanics. Our understanding of fracture in this class of solid has particularly been hindered by the incapacity of determining the competition viscous flow and fracture under finite strains. To tackle this problem, this paper presents a framework that quantitatively captures the interplay between energy dissipation and crack propagation in soft solids made of a single transient network. Using a combined analytical and numerical study, we investigate the dynamics of crack propagation at various loading rates and for networks that display different sensitivities to force. Our results point out to four different crack characteristic behaviors, for which we unveiled the respective mechanisms, all involving a strong interplay between chain deformation, bond dynamics and rupture. (C) 2020 Published by Elsevier Ltd.