A hyperelastic viscoplastic damage model for large deformation mechanics of rate-dependent soft materials

Soft materials undergo large mechanical deformation prior to failure when subjected to external loads. They exhibit nonlinearity alongside coupled elastic, viscous, and plastic behavior due to their multi-phase material composition, hierarchical structure, and multiple length and time scale effects. It is thus, mandatory to understand the nonlinear behavior of soft materials from a fundamental perspective. In this work, we propose a theoretical framework for the development of a thermodynamically-consistent coupled hyperelastic viscoplastic damage model to study the rate-dependent large deformation mechanical behavior of soft materials, subjected to a wide range of strain rates. A time-integration return-mapping algorithm is used to fit the experimental data previously reported for the human patellar tendons, hydrogels, xerogels, polymers, and sponges. Further, parametric studies are carried out to understand the mechanics of nanocellulose-loaded polyvinyl alcohol xerogels, liver tissues, PVA hydrogels, and skin tissues. It is observed that the proposed model is able to fit and predict the experimental observation with an error of less than 4%.