Enhanced multi-material 4D printing hybrid composites based on shape memory polymer/thermoplastic elastomer

An improved one-shot thermoplastic elastomer reinforced shape memory polymer (SMP) four-dimensional (4D) printing method for hybrid composite samples is proposed. Through the new reinforcement method of interlayer overlapping, the problem of inability to bond between polylactic acid (PLA) and thermoplastic polyurethane (TPU) is overcome, and the composite materials had excellent bonding properties. The feature of the improved manufacturing method is that the interface between PLA and TPU materials has continuous overlapping layers, and the boundary is wavy. Herein the complex multi-material space structure can be manufactured with a three-dimensional curved bonding surface. The shape memory and mechanical properties of the PLA/TPU hybrid composite sample are significantly improved via the improved printing method. The shape memory recovery rate of PLA/TPU hybrid composite samples are all over above 99.5%, which is close to complete recovery. The fastest recovery time is 40.61% shorter than the recovery time of the pure PLA sample, showing good shape memory cycle performance. The peak recovery force is 6.92 times higher than the recovery force of the pure PLA sample. The impact strength is 9.87 times higher than the impact strength of pure PLA sample. The composites 4D printing method can be utilized to process complex parts with excellent interfacial bonding properties, shape memory properties, and mechanical properties, which has a promising application prospect in the manufacturing of PLA-based sensors and actuators.