Shape memory polymers: A mesoscale model of the internal mechanism leading to the SM phenomena

The author's general mesomechanical concept is applied to modeling shape memory (SM) phenomena in polymers. Similarly as in other author's works devoted to SM in other materials, the concept is based on the assumption that the background of the SM phenomenon is rooted within the existence of some substructure that remains elastic throughout the process under consideration. In this approach, the description of the microscopic geometry of the structure is not necessary, it is merely assumed that the elastic substructure exists and the necessary model parameters are determined from macroscopic experiments. This leads to a macroscopic constitutive equation with tensorial internal variables. In the current study, the complicated structure of polymeric chains is not analyzed in detail; it is modeled as a medium consisting of two phases with different properties. The material's deformation in response to a complicated loading path can be successfully represented using this model, which also provides good agreement with experimental data. (C) 2007 Elsevier Ltd. All rights reserved.