Harnessing pseudoelasticity in SMA-based negative stiffness mechanical metamaterials for superior strength and recoverability

Negative stiffness mechanical metamaterials have attracted significant attention for their potential in energy dissipation and impact mitigation. However, conventional elastic designs, such as curved beams exhibiting elastic snap-through buckling, suffer from an intrinsic trade-off between recoverable energy dissipation and load-bearing capacity, greatly limiting their engineering applicability. Here, we introduce a pseudoelastic design strategy for negative stiffness curved beam metamaterials by employing a shape memory alloy (SMA) as the base material. The pseudoelasticity of the NiTi SMA enables reversible martensitic transformation at a high-level strain, which couples with structural snap-through instability to achieve recoverable energy dissipation. This synergistic mechanism offers a unique pathway to overcome the dilemma between high strength and recoverable energy dissipation. Experiments reveal that the SMA-based metamaterials exhibit both high strength and reusable, recoverable energy dissipation. Compared to their conventional metallic or polymeric counterparts, the proposed design achieves up to a 28-fold enhancement in strength and a 6-fold improvement in specific energy dissipation. The presented approach establishes a new design approach for recoverable high-strength energy-dissipating metamaterials, promising for applications in vibration control, impact protection, and adaptive structural systems.