Macroscopic characterization and phenomenological modeling of thermally-responsive shape memory polymers

Abstract

The rational design of shape memory polymer based adaptive structures requires a comprehensive examination of these materials under general multiaxial stress and strain states. This is also necessary for the identification of response functions and the evaluation of predictive capabilities of theoretical models proposed in the literature for this class of smart materials. In this paper we discuss different testing procedures and related methods of data analysis that furnish a firm experimental basis for the evaluation of functional properties of shape memory polymers (SMPs). Moreover, two broad classes of models are discussed, thermoelastic models used in the analysis of rate independent problems and thermo-viscoelastic models, which account for time effects typical for polymer materials. It is shown that the tensor-valued response functions of the general three-dimensional theory presented in this paper may be determined directly from strain/stress storage/recovery profiles measured in strain-controlled shape memory cycles performed in different deformation modes. Finally, the influence of thermo-temporal conditions on functional properties of SMPs is shortly discussed with the view of the evaluation of different classes of these materials and the corresponding theoretical models.