Constitutive and Fracture Behavior of Double-network Elastomers

The double-network (DN) concept, initially applied to hydrogels, has been adapted to elastomers,resulting in materials that combine exceptional toughness with tunable elasticity. This paper delves into the constitutive and fracture behaviors of DN elastomers, elucidating the pivotal role of prestretch and composition in tailoring their properties. We employ an incompressible hyperelastic model to predict the stress-strain behavior and energy release rate of a DN elastomer, focusing on how the interactions between the two networks influence its overall material properties. We analytically determine the influence of prestretch and composition on increasing the stiffness and energy release rate of a DN elastomer. Our analytical predictions are validated experimentally through comprehensive mechanical and fracture testing using a DN elastomer fabricated by a two-step crosslinking process to decouple the prestretch and composition. Our results show that manipulating these processing parameters can finely tune the mechanical responses of DN elastomers, optimizing them for specific applications. Our findings provide new insights into the mechanics of DN elastomers.