Strengthening Architected Instability-Based Metamaterials (AIMs)

Abstract Architected Instability-based Metamaterials (AIMs) composed of curved beams can exhibit multi-stable geometric phase transformations. By tailoring geometry and topology, AIMs can accommodate large reversible deformations while dissipating energy beyond the capabilities of conventional materials. These exceptional mechanical properties are attractive for aerospace engineering applications, including energy-absorbing components in landing gears, impact-resistant protective structures, and vibration-damping systems. Nevertheless, this very mechanism that enables reversible energy dissipation also limits its capacity, because geometric phase transformations like snap-through buckling occur at low specific strength. Thus, the reversible energy dissipation capability cannot be easily leveraged in aerospace applications. In this work, we propose a theoretical and numerical modeling integrated approach to manipulate the out-of-plane stiffness distribution of curved beams. Compared to the conventional AIMs with uniform curved beams, the strength of the proposed beam configuration can be largely improved, while the local maximum strain remained relatively lower during phase transformations. Finite element analysis and experiments show this approach mitigates the local strain concentration effects of AIMs. Without inducing unreversible plastic deformation, the mechanical properties like the maximum peak strength, trapped energy during compression, and energy dissipation under cyclic loading can be increased by 62.1%, 82.5%, and 45.6%, respectively.