Structural modifications of hexa-chiral auxetics for lightweight energy absorption

Auxetic materials, characterized by their negative Poisson’s ratio, exhibit a unique deformation behavior and exceptional energy absorption properties. This study focuses on the structural modification of a hexa-chiral auxetic structure to enhance its energy absorption capacity by counteracting premature buckling of boundary layers and cylindrical units. Hence, the standard hexa-chiral configuration is modified by introducing connective struts at the edges to homogenize the stress distribution and thus ameliorate the mechanical behavior. Additionally, further struts are introduced in the center of each cylindrical unit, counteracting local compression, thereby significantly enhancing the energy absorption without vastly inflating the relative density. These struts were slightly angled to account for the rotational movement induced by the deformation of connective struts. As a result, the mass-specific energy absorption increased by up to 63%, while the Poisson’s ratio of the auxetic structure decreased from to . Results thus demonstrate that strategic geometric alterations significantly increased energy dissipation and improved mechanical robustness. A second set of structures is printed from a brittle resin, highlighting that sufficient ductility of the base material is required to allow structural deformation over material-based failure. It is also shown that manufacturing related inaccuracies can severely limit auxetic deformation.