Journal of Applied Polymer Science, Vol.125, No.6, 4390-4401, 2012
New constitutive modeling for time-dependent mechanical behavior of polymers close to glass transition: Fundamentals and experimental validation
The 1D limit of a 3D visco-hyperelastic model is discussed and validated using a rich and rigorous database obtained on PMMA above Tg. Inelastic phenomena are accounted for as an evolution of internal variables assumed to be related to the alteration of microstructure that induces changes in well chosen constitutive parameters and dissipation of energy. Inelastic strain-rate is deduced from energy balance between elastic and dissipative phenomenon. The concept allows introducing time effects in any rubber elasticity theory, resulting in a visco-hyperelastic model consistent with continuum thermodynamics. In this article, Edwards-Vilgis' model is used as the core and extended to a general time dependent constitutive model. Phenomenological models for disentanglement or crystallization are suggested that allow reproducing all viscoelastic effects using one unique model. An accounting for temperature and strain-rate effects by an a priori uses of time temperature superposition principle is also proposed. The three concepts result in an original model of high efficiency. This new approach is a highly attractive way of modeling time dependent behavior of polymers over a wide range of temperature and strain-rate up to large strains. This is demonstrated in the case of PMMA. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012