Study on Bionic Lattice Structures Inspired by Walnut with Characteristics of Negative Stiffness and Double Stress Phases

Abstract

Based on the walnut multi-ridge outer shell and cosine-like inner shell structure, bionic-inspired walnut lattice structures coupled by outer curved beams and inner filler structures were designed. The protective capabilities of these structures were evaluated under quasi-static compression and low-speed impact conditions using experiments and numerical analysis. The bionic-inspired walnut lattice structures were found to possess two stress phases The outer curved beams displayed a notable negative stiffness response in stress phase 'I' to repeatedly dissipate small impact energy. The inner filler structures displayed higher stress levels in stress phase 'II' to dissipate large impact energy. The specific energy absorption of the bionic-inspired walnut lattice structures with filling structures improved by at least 48.6%. The impact resistance of the lattice structures was validated through impact simulation, indicating that a higher impact rate enhances the deformation stability of the curved beams.

Keywords: Bionic, Energy dissipation, Negative stiffness, Deformation mode