A modified phase‐based constitutive model for shape memory polymers

ABSTRACT Constitutive models used for predicting the thermomechanical behavior of shape memory polymers (SMPs) are critical for the development of SMP applications. Among the existing models, the phase transition concept attracts wide attention due to its good predictive capacity and great convenience. However, most of the present phase transition models for SMPs have limitations or deficiencies in considering the effect of temperature change rate on the thermomechanical behavior of SMPs. In this paper, based on the kinetics of phase transitions, we propose a constitutive model in which the temperature change rate is incorporated into the phase evolution function to consider the effect of the temperature change rate on the thermomechanical properties of SMPs. Then experimental data under different recovery conditions for two different types of SMP materials are used to validate the predictive capacity and versatility of the present model. The predicted results agree quite well with the experimental observations, which demonstrates that the present model is robust enough to predict the complex thermomechanical behavior for different SMPs. In addition, through experiments and model predictions, we find that the shape free recovery curves at different heating rates can be easily predicted by just moving a reference recovery curve along the horizontal direction by a distance whose value is calculated through the proposed equation. © 2018 Society of Chemical Industry