Shape memory property and mechanism of the knitting-fabric reinforced epoxy composites subjected to tensile loading

Abstract

Shape memory polymers (SMPs), as stimulus-responsive shape-shifting materials, are generally reinforced with particles and fibers to fabricate the shape memory polymer composites (SMPCs) for better mechanical and shape-recovery properties. However, many continuous fibers reinforced SMPCs have good shape recoverability subjected to bending loading but limited shape recoverability under tensile loading due to limitation of tensile deformation of continuous fibers. Here, we developed the continuous fiber knitting-fabric reinforced shape memory epoxy composites and investigated their shape memory property and mechanism subjected to large tensile strain. The effect of epoxy component ratios, tensile strains, and course(0°)/wale(90°) directions on the shape memory behavior, recovery stress, and mechanical property of the shape memory epoxy (SMEP) and its composite (SMPC) were studied. The results show that the SMEPs and SMPCs with the tensile strain up to 30% have good shape fixation rates of above 99% and final recovery ratios of above 98%. A mesoscopic finite element model of knitting-fabric reinforced SMPC was established to study the shape memory mechanism. The recovery stress of the SMPC can improve up to 5.8 times as compared with pure SMEP. The knowledge gained in this work will benefit future development and application for better actuators.