Studies on the Shape Frozen/Recovery Behaviors of SMP-based Sandwich Structure:

Shape memory polymers (SMPs) are polymers that can change between temporary and permanent shapes via a programmed thermo-mechanical cycle. However, the stiffness and shape recovery stress of SMPs are much low as compared with shape memory alloys and ceramics. This article aims to improve their stiffness and shape recovery stress by utilization of sandwich structures. Two types of SMP-based sandwich beams, aluminum/SM-polyurethane/aluminum, and steel/SM-polyurethane/steel were considered. Theoretical solutions were proposed in describing the shape frozen/recovery behaviors, which include mechanical loading at an above temperature, frozen fixture by decreasing the temperature to be lower than Tg, and shape recovery through reheating the temperature to be higher than Tg. The results confirm that SMP-based sandwich structure can significantly improve the shape recovery stress and meanwhile realize an acceptable shape fixture rate.