Cyclic Properties of Energy Dissipation and Storage in a Film Made of Shape Memory Polymer of the Polyurethane Series.

Abstract

By examining the stress strain relationship in a film made of shape-memory polymer of polyurethane series through cyclic loading at and above the glass transition temperature Tu, the properties of energy dissipation and storage were investigated. The results are summarized as follows. (1) Although yield stress decreases and irrecoverable strain appears after the initial loading at and above Tg, stress-strain curves vary slightly thereafter. Therefore, in order to obtain constant cyclic deformation properties in practical applications, mechanical training with one cycle is effective. (2) The rate of energy dissipation is 0.6∼0.7 in the case of loading at Tg. Therefore, its capacity as a damping material is excellent at Tg. The higher the strain rate and the maximum strain, the larger the dissipated work. (3) The energy storage efficiency is 0.7∼0.8 in the case of loading above Tg. Therefore, the performance as a energy storage material is high above Tg. The amount of recoverable strain energy is almost the same at and above Tg. (4) The performance as a damping and energy storage material is effective if the polymer element is of a large scale and is subjected to large deformation.