Effect of Geometric Parameter α on the Performance of 3D Printed Four-Pointed Star-Shaped (FPSS) Auxetic Structures Inspired by Marine Geometry

A bioinspired 3D-printed auxetic metamaterial, modeled after the geometry of a four-handed starfish, is presented in this study. The structure, which consists of Four-Pointed Star-Shaped (FPSS) gaps, displays strong auxetic behavior and high energy absorption, showcasing a novel approach to metamaterial design. The metamaterial was fabricated using Digital Light Processing (DLP), and a compression test was performed to assess its auxetic behavior. The structure was compressed along the [Formula: see text]-direction, and the resulting force-displacement curve revealed two distinct deformation phases, with a sharp increase in force followed by a decrease in the rate of increase, reaching a steady state. To further understand the material’s behavior, simulations were conducted. Stress and strain distributions were analyzed, which revealed that the maximum stress and strain were concentrated along the [Formula: see text]-direction, particularly in the diamond-shaped regions of the structure. The influence of the angle [Formula: see text], which defines the distance between the tips of the star-shaped gaps, was examined through simulations for angles of [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text]. Results indicated that decreasing the [Formula: see text] angle led to more pronounced elastic strain, while the stress distribution showed the opposite trend. The required compressive force decreased as the [Formula: see text] angle increased, with maximum forces of 4.25[Formula: see text]kN, 3.85[Formula: see text]kN, and 3.28[Formula: see text]kN for angles of [Formula: see text], [Formula: see text], and [Formula: see text], respectively. It was also found that reducing the [Formula: see text] angle from [Formula: see text] to [Formula: see text] resulted in a significant increase in energy absorption by 28.2%. These features suggest that the FPSS metamaterial has considerable potential as a core design element in next-generation spinal implants.