Design, analysis and optimization of the uniaxial properties of a new auxetic anti-chiral parallelogram metamaterial

An innovative two dimensional auxetic metamaterial was designed by mirroring a parallelogram
with two parallel ligaments along the horizontal and vertical directions. The architecture of the
metamaterial is based on the adoption of a structural chiral deformation mechanism induced by the
rotation of the connecting joint of the parallel ligaments. A parametric study was performed to
investigate the in-plane equivalent mechanical properties of this anti-chiral parallelogram (ACP)
metamaterial and auxetic parallelogram honeycombs from open literature using theoretical and
numerical models. The NSGA-Ⅱoptimization algorithm has also been adopted to identify the
optimal Pareto fronts for the maximum non-dimensional Young’s modulus and minimum Poisson’s
ratios for the two classes of auxetic metamaterials. The optimization process indicated that the new
ACP metamaterial possessed larger stiffness within specific ranges of Poisson’s ratios. Quasi-static
compressive experimental tests in linear and nonlinear regimes with finite element simulations have
been carried out to verify the results of the optimal configurations . The energy absorption
performance of the new ACP metamaterial has been also evaluated for different combinations of
parameters. The good tunability of the mechanical properties of this new auxetic metamaterial
suggest potential engineering applications for general biomedical prosthesis and energy absorption
purposes.