On a new thermodynamic description of viscoelastic materials

A new thermodynamic approach, based on extended irreversible thermodynamics, is proposed to describe viscoelastic materials. The state space is widened by including the stress tensor and the heat flux vector among the set of independent state variables. These extra variables are satisfying evolution equations taking the form of first order time differential equations. The present formalism encompasses the classical models of Maxwell, Kelvin-Voigt, Poynting-Thomson as well as the thermoelastic body and the Newtonian fluid. This is achieved without appealing to an artificial decomposition of the stress and strain tensors into elastic and inelastic parts.