Size‐Effect Stiffening and Densification Strain Regulation Shape Micro Metamaterials for Ultra‐High, Cycle‐Stable Energy Absorption

Abstract

ABSTRACT Thin‐walled metamaterials hold great promise for energy absorption, yet a fundamental conflict persists between high energy absorption and cycle stability in most existing designs, which is the key challenge for applications of these materials. Here, a new kind of energy‐absorbing and cycle‐stable integrated (ECI) microscale metamaterials are presented that overcome this limitation, surpassing conventional thin‐walled metamaterials in compression strength and energy absorption by 1–4 orders of magnitude. Cyclic loading experiments show that the programmable ECI micro metamaterials retain 87% of their energy absorption capacity after multiple cycles. These breakthroughs stem from a novel design methodology that harnesses size‐effect‐induced bending stiffness enhancement together with densification strain regulation. Guided by this approach, the rotatable frames with tunable densification strain and curvature‐optimized micro shells with enhanced bending stiffness were innovatively coupled, leading to a 630% improvement in compressive strength and energy absorption over macroscale equivalents. Dynamic characterization reveals that the optimal ECI micro‐metamaterial significantly outperforms conventional energy‐absorbing materials and lattice structures, specifically exceeding them by an average of 124% in rebound attenuation. This work redefines the performance envelope of thin‐walled metamaterials and provides a new paradigm for designing ultra‐robust protective systems through geometric‐stiffness hybridization.