Viscoelastic properties of filled rubber. Experimental observations and material modelling

The rate-dependent behaviour of carbon-black filled rubber is investigated in compression regimes. The viscosity-induced rate-dependent effects are described. The time independent response of the rubber is modelled by the Mooney-Rivlin hyperelastic material with uncoupled volumetric/deviatoric free energy function. The non-equilibrium viscoelastic stresses are evolving internal variables governed by rate equations proposed by Simo (1987). The parameters of a constitutive model of finite strain viscoelasticity are determined by nonlinear optimization methods. The implementation in Comsol Multiphysics of the material model for the viscoelastic stress response at large strains is presented. The FE simulation uses the finite strain formulation based on the material configuration with the right Cauchy-Green tensor as the strain measure. The FE simulations of the elastomeric viscoelastic solids response in relaxation, creep and cyclic loading are presented.