The properties of metamaterials with negative Poisson’s ratio (with an auxetic structure based on a cell in the form of a concave hexagon) to resist penetration by a rigid spherical striker along the normal were experimentally studied. Using a 3D printer, samples of the same mass with a chiral and non-chiral structure were made from flexible thermoplastic polyurethane (TPU 95A plastic) and rigid e-PLA plastic, which were compared by the ability to reduce the kinetic energy of strikers at a speed of about 190 m /s. It was found that the chirality of the sample structure (for both TPU and PLA plastics) leads to an increase in their protective properties. However, when the sample structure was rotated by 90 degrees, the samples without chirality showed the best resistance to penetration. Based on the results of a series of experiments with TPU and PLA samples, the most effective in terms of resistance to penetration by a striker were auxetics made of thermoplastic polyurethane, with a non-chiral structure turned by 90 degrees.
S. Yu. Ivanova (Wed,) studied this question.