Synergistic design of curved beam metastructures with tunable stiffness, Poisson's ratio and energy absorption ability

Abstract

Mechanical metastructures have garnered widespread attention due to their superior mechanical properties. However, how mechanical metastructures achieve bidirectional mechanical responses while enabling synergistic multi-performance design remains an issue worthy of in-depth investigation. In this study, four types of curved beam metastructures (CBMs) are proposed, named CBM-I, CBM-II, CBM-III, and CBM-IV. The mechanical responses of these CBMs, including stress-strain curves, energy absorption capabilities, and deformation profiles, are studied through finite element simulations and experiments. The results show that both CBM-I and CBM-II exhibit negative stiffness characteristics along the X and Y directions, while offering customizable deformation lengths. When compressed to a densification state, the stress-strain curves of CBM-I and CBM-II demonstrate a three-stage plateau feature. CBM-III not only achieves the transformation of nonlinear properties such as positive stiffness, quasi-zero stiffness, and negative stiffness but also features a tunable Poisson’s ratio, which cannot be accomplished by conventional negative-stiffness metastructures. CBM-IV exhibits excellent capability of sign switching for Poisson's ratio. The frame-reinforced design and double curved beam design strategies not only improve the peak force of CBMs but also suppress the asymmetric buckling deformation of the curved beam and enhance structural stability. The quasi-zero stiffness and customizable length characteristics of CBM-I and CBM-II give them significant application value in morphing wings. This study provides valuable insights for the multifunctional design of novel tunable CBMs and promotes their application in aerospace engineering.