4D printed continuous fiber-reinforced self-locking Miura-ori composites with high energy absorption and cyclability

The shape memory effect allows stimuli-responsive materials to generate programmable morphing when subjected to external stimuli, facilitating the creation of active origami with 2D-to-3D shape transformation capabilities. However, the current active origami made of polymer-based stimuli-responsive materials exhibits poor mechanical performance due to the inherent low stiffness of materials, which hinders their exploration and engineering application. This work reported a novel fabrication and design method to construct 3D continuous fiber-reinforced self-locking Miura-ori (SLMO) composites with high energy absorption and cyclability by 4D printing of shape memory composites. The SLMO structure consists of a Miura-ori unit and a highly stretchable bottom stopper panel, where the Miura-ori unit actively morphs and locks into a predetermined configuration under external stimuli and the constraint of the stopper panel. Incorporating continuous fibers enhanced the strength of the Miura-ori facets, synergizing with the highly stretchable characteristic of the bottom panel to enable the SLMO structure to exhibit a push-to-pull deformation mode under compressive load. Structural analysis of the SLMO, stress-stretch behavior of the bottom panel, and buckling criteria of the Miura-ori facets were theoretically investigated to describe the push-to-pull deformation behavior of the SLMO structure and the conditions necessary for its realization. Moreover, the compressive behavior of the SLMO structure with different design parameters was investigated through experiments and theoretical analysis. By optimizing design parameters, it was demonstrated that the SLMO structure can sustain more than 10 cycles of 50% compressive strain. This approach broadens the practical and functional applications of active origami.