RESEARCH ON REUSABLE PROPERTIES OF MULTISTABLE METAMATERIAL OF HIERARCHICAL CURVED BEAMS

Multistable metamaterials have garnered widespread research and application due to their excellent mechanical properties. However, existing literature has primarily focused on single curved beam structures, while the study of the repeatable energy absorption characteristics of multistable metamaterials constructed from hierarchical curved beam unit cells remains limited. Furthermore, compared to conventional materials, the fatigue performance of multistable metamaterials under cyclic loading has been relatively unexplored. In this paper, a curved beam unit cell was constructed using the first-order buckling mode of a straight beam with fixed ends as the initial configuration. This unit cell was then employed to create a bi-material bistable unit through 3D printing technology. Subsequently, a hierarchical curved beam structure was established, and empirical formulas yielded more precies results compared to the previous third-order and fourth-order polynomial formulations. By employing the double-curved beam unit cell as the fundamental building block, a three-dimensional DOT multistable metamaterial was designed through center rotation, and its steady state performance and mechanical characteristics were thoroughly investigated. The structural mechanical response was investigated by conducting parametric analyses to examine the influence of unit geometric parameters and modular topology configuration. Finally, fatigue experiments were performed to demonstrate the reusability of this type of multistable metamaterial. The proposed structure enables the transition between positive and negative stiffness within the small and large deformation range. Moreover, the deformation exhibits elastic stability, indicating that the Young's modulus remains relatively constant. The structure also possesses multi-stable, programmable, and repeatable energy absorption characteristics. The effective crushing distance and energy absorption efficiency of the double curved beam increase with the geometric parameter Q. The design strategy presented in this study opens up new avenues for fabricating mechanical metamaterials capable of multi-step reversible deformation, thereby offering a novel approach for engineering materials design that integrates material properties, structural behavior, and functional attributes.