Study of Resistance to Impact Penetration of Auxetic Metamaterials at Various Angles of Rotation of Their Internal Cellular Structure

The resistance of auxetic metamaterials based on a cell in the form of a concave hexagon (with a negative Poisson’s ratio) to penetration by a rigid spherical striker along the normal was experimentally studied. Samples of metamaterials with a chiral and non-chiral internal structure were made on a 3D printer from flexible thermoplastic polyurethane (TPU 95A plastic) and rigid e-PLA plastic. For all four types of metamaterials, samples were prepared whose internal structure differed in the rotation angle (0, 30, 60, or 90°) relative to the vertical axis. The samples were compared by their ability to reduce the kinetic energy of strikers at a speed of about 190 m/s at a temperature of 16°C. It was found that auxetics made of thermoplastic polyurethane with a non-chiral structure rotated by 90° are the most effective in terms of resistance to striker penetration. The dependence of the striker deviation on exit from the samples (up or down) on the direction of rotation of the internal structure of the sample at an angle from 0 to 90° clockwise or counterclockwise, respectively, was revealed.