Enhanced shape memory performance and numerical simulation of knitted-fabric reinforced polymer composites with weft yarns

Fabric-reinforced shape memory polymeric composites (SMPC) have shown great potential in the design of intelligent deformation structures. In this work, the weft-knitted fabric inserted with weft yarns was developed as reinforcement to fabricate the shape memory epoxy polymer (SMEP) composites. The effects of weft yarn, loop density and direction on the shape memory performance of SMPC under different bending radii were experimentally investigated. The results show that the SMPC have good shape fixity ratios and shape recovery ratios of around 98%. As compared with those of SMPCs without inserting weft yarns, the SMPCs with weft yarns have shorter shape recovery time, and the recovery force of SMPCs with weft yarns in the 0° and 90° directions shows an increase of 86.4% and 79.5%, respectively. The recovery force of SMPC improve 3.7 times compared to SMEP. The multiscale models of SMPC were established with basis of the results of micro-computed tomography scanning of specimens and viscoelastic theory. The surface buckling behaviors of SMEP and SMPC specimens after U-bending load were discussed. Finally, the deformation of loops and weft yarns of SMPC were analyzed to reveal the shape memory mechanism. Highlights: Shape memory polymeric composites (SMPC) with weft yarns has shorter shape recovery time. Recovery force of SMPC with weft yarns was obvious enhanced. Multi-scale viscoelastic models of SMPC were established. Surface buckling behaviors of SMPC after U-bending load were revealed.