Realization of Auxetic Mechanical Meta Structure with Improved Load Bearing Capability by Additive Manufacturing

Auxetic metamaterials are a specific type of metamaterial that exhibits a negative Poisson’s ratio. In other words, it is a type of structure that, when compressed vertically, contracts in the lateral direction, as opposed to most materials that expand in the lateral direction. This is due to the specific structure of the metamaterial. Additionally, many of these structures have high energy absorption and low densities, which makes them desirable in many industries, including the aerospace, body armor, and medical fields. Hexachiral auxetic metamaterials, a new design of negative Poisson’s ratio materials, offer many benefits to the engineering world in the form of improved specific strengths and energy absorption. Due to their recent introduction to the realm of metamaterials, there are few studies surrounding them, and the available designs tend to be unoptimized in terms of their load-bearing capacity. This study provides insight into the design and optimization of a novel ligament structure for layered chiral metamaterials. Stress reduction methods are employed to develop a general improved structure. Subsequently, parametric analysis provided the optimal design to maximize load bearing capacity without sacrificing Poisson’s ratio. Similar structures of comparable strength lack comparable Poisson’s ratios to match. The high negative Poisson’s ratio of the design lends greatly to various applications. Furthermore, existing layered chiral designs can use this study as a base for similar optimization. Once a final design was chosen, physical compression testing was performed to determine the load-bearing capacity. Once analyzed, the FEA and physical testing results matched and exhibited massive increases in the load-bearing capacity with a slight increase in the Poisson’s ratio.