Shape memory performance and mechanical properties of natural fiber-reinforced polymer composites enhanced via fabrication strategies

Natural fibers reinforced polymeric composites have good mechanical properties and environmental protection features but lack functionality. The natural fiber reinforced shape memory polymer composites (SMPC) were fabricated with four processes using flax yarns (FF), spandex filament (SP) and short flax fibers (SF) as reinforcement materials. The effects of fabric structure, cutting orientation angle, spandex content and short fiber content on shape memory performance and mechanical properties of natural fiber reinforced SMPC were studied. The results show that the shape fixity rates of the SMPCs keep above 98 %. The shape recovery ratio of FF-Plain-0° SMPC is 83.2 % at 480 s while the shape recovery ratio of FF-Plain SMPC with cutting angle of 45° can reach 99.3 % at 300 s. The FF-Satin-0° SMPCs achieve the highest shape recovery force of 2.7 N, which is 1.8 times than that of FF-Plain-0° SMPCs. The spandex filament as reinforcement phase can improve the shape memory properties of SMPCs. As compared with FF-Plain-0° SMPC, the shape recovery ratio and shape recovery force of 4FF/1SP SMPC with addition of spandex elastic filament increase by 10.0 % and 46.7 %. The short fiber as reinforcement phase can improve the flexural strength and modulus of FF/25SF SMPCs by 15.3 % and 10.9 % as compared with FF-Plain-0° SMPC, respectively. The FF/SP/SF-45° SMPCs with integrated optimization of process conditions have good shape memory properties and mechanical properties. This study contributes to the development and optimization of smart SMPCs with natural fibers.