Study on elastic mechanical properties of novel 2D negative Poisson’s ratio structure: Re-entrant hexagon nested with star-shaped structure

To overcome the disadvantages of the re-entrant hexagonal cell (RHC) whose negative Poisson's ratio characteristic depends on the base angle, and the star-shaped cell (SSC) whose Young's modulus is small, a novel re-entrant hexagon structure nested star-shaped cell (RNSC) is proposed in the present paper, made of RHC nested with SSC. The expressions of the effective Young’s modulus and Poisson’s ratio of RNSC in two orthogonal directions are derived using the energy method. The superiority of the elastic mechanical properties of RNSC under the same relative density is verified, i.e., Young's modulus is improved by embedding SSC in RHC, and Poisson's ratio keeps negative. Parametric analyses are carried out, and the most sensitive parameter is carried out. The uniaxial tensile test is carried out to verify the advantages of elastic mechanical properties of RNSC, and when it is used as a protected structure, the bearing capacity in the X-direction is stronger and the energy absorption in the Y-direction is stronger. The novel RNSC can effectively regulate the effect of negative Poisson’s ratio and can improve the effective Young’s modulus with the appropriate parameters while ensuring the lightweight, and these are the advantages in the application of protected structures.