poisson's ratio assessment of different auxetic structures with and without nonlinear geometric effects

unlike traditional materials, when an auxetic material is stretched, it expand laterally and when it is compressed, it tend to get thinner. these extremely unusual materials do not defy the laws of elasticity theory. it is only in the last 12 years that any such material also known as negative poisson ratio material has been fabricated. in this paper different shape of auxetic structures such as anti-tetra-chiral, missing rib structure, re-entrant structures have been evaluated numerically and analytically to investigate the poisson ratio of different structural shapes.