Rigid-flexible coupling modular mechanical metamaterials with tunable elasto-plastic properties

With their inherent assembly flexibility and unique self-locking effect, modular structures have acquired potential applications in portable protection. However, like traditional structures, most modular metamaterials have limited stiffness tunability due to material constraints, and the lack of component universality restricts their performance and applicability. To overcome these limitations, inspired by the rigid-flexible coupling in Chinese Tai Chi, a universal modular mechanical metamaterial based on the honeycomb deconstruction and multi-layer bistable beams is proposed to enable the regulation of elastic stiffness from individual components to hierarchical sequences. The quasi-static and dynamic mechanical behavior is studied through experiments and numerical simulations. The results indicate that introducing soft components enhances specific energy absorption and achieves comparable capacity to the integrated structure, while under impact, the rigid-flexible modular metamaterial reduces peak force by 63.8% and delays its occurrence. Additionally, the self-locking mechanism is found to result from the elasto-plastic deformation caused by compressive expansion and bidirectional three-point bending of the components. In the rear-end simulation, the rigid-flexible modular bumper boosts impact mitigation by 80% and reduces maintenance costs by 85.7%. These results reveal the rigid-flexible modular metamaterial with component interchangeability and tunable performance, offering a valuable solution for rapid, low-cost deployment in advanced protection.