Porous Materials with Omnidirectional Negative Poisson's Ratio

TL;DR

This paper introduces a novel two-dimensional perforated sheet with a hexagonal pattern that exhibits omnidirectional negative Poisson's ratio, confirmed through simulations and experimental tests, offering a simple and versatile auxetic material for engineering uses.

Contribution

The study demonstrates a new isotropic auxetic medium with negative Poisson's ratio achieved via a specific perforation pattern, validated by both numerical and experimental methods.

Findings

Negative Poisson's ratio achieved for specific hole dimensions and orientations.

Experimental validation using Digital Image Correlation techniques.

The structure is easy to fabricate and applicable in engineering fields.

Abstract

This paper presents an auxetic medium, consisting of a two-dimensional perforated sheet where the holes are arranged in a repetitive pattern. The hexagonal disposition of the perforations makes the medium isotropic in the plane. It is shown that negative values of the Poisson's ratio can be achieved for specific values of the dimensions and orientations of the holes. The results of the numerical simulations are confirmed by experimental tests, in which the Poisson's ratio of each specimen examined is evaluated from the displacement field obtained from the Digital Image Correlation (DIC) technique. The distribution of stresses in the medium is determined directly from photoelastic images. The auxetic structure proposed in this paper is easy to fabricate and can be very useful in several engineering applications.