Cross-linking degree modulation of 4D printed continuous fiber reinforced thermosetting shape memory polymer composites with superior load bearing and shape memory effects

While 4D printing technology can effectively simplify the manufacturing process of complex spatially deployable structures and improve material utilization, its sustainable development still faces challenges due to the inferior mechanical load bearing properties of the printed materials. In this study, continuous fiber-reinforced thermosetting shape memory polymer (CF/Ts-SMP) 4D printing technology was employed to attain superior load bearing and shape memory functions of structures. The mechanism of Ts-SMP cross-linking degree on the printing rheological, thermomechanical, mechanical load bearing and shape memory properties of composites was investigated. With 5 % curing agent content, the 4D printed CF/Ts-SMP composites was in moderate cross-linking degree and showed superior overall mechanical and shape memory properties, with a bending strength of 806.38 MPa, a flexural modulus of 47.2 GPa, a shape fixation ratio of 98.46 %, and a shape recovery ratio of 99.01 %. Based on this, complex sandwich pod structure was further printed, which have potential future applications in the fields of space-deployable structural hinges and robot deformable joints.