Geometry-related energy damping behavior of additively manufactured NiTi bionic structures

This study investigates the influence of the topological configuration on cyclic energy characteristics of NiTi bionic lattice structures. Inspired by the saddle-shaped exoskeleton of Campylodiscus, bionic lattice structures (BLSs) with varying mean curvatures (K) and gradient modes were designed and fabricated by laser powder bed fusion (LPBF). In contrast to the straight-strut-based body-centered cubic (BCC) structure, BLSs composed of saddle-shaped unit cells exhibited better surface quality and specific damping capacity (SDC). The surface deviation range of the BLSs decreased with increasing K due to enhanced self-supporting capability. Both total specific energy dissipation (SED) and mean SDC of BLSs showed positive correlations to mean curvature, which was attributed to the more uniform stress distribution and increased stress-induced martensitic transformation (SIMT). K_0.7 exhibited the highest total SED of ∼0.543 J/g and a mean SDC of ∼0.644. The SED per cycle was insensitive to gradient modes, while the central gradient (CG) enhanced the total SED by increasing the ultimate strain and the cycle number. Notably, the SDC of the BLSs was structurally dependent at small strains, while it depended on the material properties of NiTi at high strains. The findings could serve as a reference for developing reusable energy absorbers.