Nonlinear Viscoelasticity and Generalized Failure Criteria for Biopolymer Gels

TitleNonlinear Viscoelasticity and Generalized Failure Criteria for Biopolymer Gels
Publication TypeJournal Article
Year of Publication2017
AuthorsKeshavarz B., Divoux T., Manneville S.A, McKinley G.H
JournalACS Macro Letters

Polymer gels behave as soft viscoelastic solids and exhibit a generic nonlinear mechanical response characterized by pronounced stiffening prior to irreversible failure, most often through macroscopic fractures. Here, we describe this scenario for a model protein gel using an integral constitutive equation built upon the linear and the nonlinear viscoelastic properties of the gel. We show that this formalism predicts quantitatively the gel mechanical response in shear start-up experiments, up to the onset of macroscopic failure. Moreover, we couple the computed stress response with Bailey’s durability criterion for brittle solids in order to predict the critical values of the stress σc and strain γc at failure. The excellent agreement between theory and experiments suggests that failure in this soft viscoelastic gel is a Markovian process and that Bailey’s failure criterion extends beyond hard materials such as metals, glasses, or minerals.