Shape recovery properties of 3D printed re-entrant strip using shape memory thermoplastic polyurethane filaments with various temperature conditions

In this research, to confirm the applicability as the actuator of the re-entrant (RE) structure strip using 3D printing with shape memory thermoplastic polyurethane material, two types of 3D printing infill conditions and five extension temperature conditions were applied. REstrip was analyzed through differential scanning calorimetry (DSC), tensile properties, Poisson’s ratio properties, and shape recovery properties according to temperature conditions. The DSC results showed that the glass transition temperature peaks of the SMTPU filament and the 3D printed REstrip were in the range of about 30–60 °C. In terms of tensile properties, the initial modulus, maximum stress, and yield stress of REstrip all decreased, while the elongation at break increased with increasing extension temperature. In terms of Poisson’s ratio, it was confirmed that as the extension temperature rises, Poisson’s ratio shows a positive value at a lower elongation, and the deformation is best at 50 °C. As a result of the shape memory property, the shape recovery ratio tended to decrease as the tensile deformation temperature increased.