On the Effect of Pore Shape and Size on the Auxetic Properties of Perforated Sheets Based on the ‘Rotating Squares’ Model

The classic auxetic perforated sheets with diamond‐shaped voids reproducing the rotating‐square topology are re‐investigated and optimised via the incorporation of additional triangular voids at the edges of each diamond perforation. The scope is to make these systems lighter and render their pores more suitable for applications that require particular geometric features. Results show that the addition of such small‐ to medium‐sized triangular voids did not have much effect on the extent of auxetic behaviour compared to the equivalent system having just diamond‐shaped voids. This is rather remarkable given the very noticeable change in pore shape and size and the reduction in solid material and density. We also show that the exact magnitude of the Poisson's ratio may be fine‐tuned through careful choice of various geometric parameters. All this broadens the potential of perforated auxetic systems for lightweight structural design and applications where specific pore geometries are required.