Refinement of a 3D finite strain viscoelastic constitutive model for thermally induced shape memory polymers

Abstract

Refinement of a previously developed 3D finite strain viscoelastic constitutive model for thermally induced shape memory polymers is proposed. In the previous model, the temperature-dependent material parameters consist of two parts: parameters at high and low temperatures. In addition, six parameters are fitted simultaneously only based on a single curve of initial elastic modulus, incurring difficulty in parameter identification. In this paper, the parameters at high temperature are derived from those at low temperature by using a modified Adam-Gibbs model and Arrhenius-type of time-temperature superposition shift factor. In addition, by introducing a physics based viscosity parameter, only three parameters are needed to be determined by the curve of initial elastic modulus. The number of material parameters is thus reduced from seventeen in the old model to thirteen, and the material parameter identification process is much easier to be implemented. Finally, the refined model is validated by comparing with three experimental sets of free recovery from the literature.

Keywords

• Shape memory polymer
• Finite strain
• Viscoelastic
• Constitutive model