Dual-stage mechanical response and energy dissipation in double-negative metamaterials

A novel three-dimensional double-negative mechanical metamaterial is proposed. The negative Poisson’s ratio (NPR) and negative stiffness (NS) are coupled through cosine-shaped curved beams and inclined rib elements. This coupling enhances the metamaterial's impact resistance and energy dissipation capabilities. Finite element simulations and quasi-static compression experiments were conducted to systematically investigate the influence of geometric configurations with varying thickness ratios on mechanical responses. The results indicate that the Type II configuration exhibits a pronounced NPR effect (−0.77) and dual-peak negative stiffness behavior, with two distinct buckling stages observed in the force–displacement curves. The total energy absorption (EA) reached 17.95 J, representing improvements of 150.2% and 55.0% compared to the Type I and Type III structures, respectively. The specific energy absorption (SEA) peaked at 221.56 J/kg. The proposed double-negative metamaterial enables tunable mechanical responses through geometric modulation and shows significant potential in energy absorption, impact mitigation, and vibration suppression.