Experiments and modeling of the coupled viscoelasticity and Mullins effect in filled rubber materials

Filled rubber-like materials are widely used in engineering applications, and are known to exhibit a rate-dependent non-linear inelastic behavior, and stress-softening, also known as the Mullins effect is frequently encountered. In this work, we characterized and modeled the constitutive response of a handful of commercially available filled rubber-like materials. We first perform a set of large-deformation uniaxial experiments at room temperature and at multiple rates. Those experimental findings are used to develop and calibrate a thermodynamically consistent constitutive model, which is then numerically implemented in a finite element package by writing a user material subroutine. The constitutive model is validated by comparing the results of an inhomogeneous experiment and simulation. A key finding of this work is that the mechanisms that cause the Mullins effect appear to be the main drivers of viscoelasticity in the materials used here.