Characterizing and modeling the free recovery and constrained recovery behavior of apolyurethane shape memory polymer

Abstract

In this work, tensile tests and one-dimensional constitutive modeling were performed on ahigh recovery force polyurethane shape memory polymer that is being considered forbiomedical applications. The tensile tests investigated the free recovery (zero load) responseas well as the constrained displacement recovery (stress recovery) response at extensionvalues up to 25%, and two consecutive cycles were performed during each test.The material was observed to recover 100% of the applied deformation whenheated at zero load in the second thermomechanical cycle, and a stress recovery of1.5–4.2 MPa was observed for the constrained displacement recovery experiments.After the experiments were performed, the Chen and Lagoudas model was used to simulateand predict the experimental results. The material properties used in the constitutivemodel—namely the coefficients of thermal expansion, shear moduli, and frozen volumefraction—were calibrated from a single 10% extension free recovery experiment. The modelwas then used to predict the material response for the remaining free recovery andconstrained displacement recovery experiments. The model predictions match well with theexperimental data.