A novel layered topology of auxetic materials based on the tetrachiral honeycomb microstructure

TL;DR

This paper introduces a new bi-layered auxetic honeycomb structure based on tetrachiral microstructures, validated through analytical, numerical, and experimental methods, demonstrating enhanced mechanical properties and negative Poisson ratios.

Contribution

The paper proposes a novel bi-tetrachiral topology that leverages opposing chiral layers to achieve superior auxetic properties and improved elastic moduli.

Findings

Bi-tetrachiral structure exhibits higher Young's modulus than single-layer tetrachiral.

Experimental validation confirms strongly negative Poisson ratios in the new topology.

Theoretical models accurately predict the mechanical behavior of the bi-layered auxetic material.

Abstract

Microstructured honeycomb materials may exhibit exotic, extreme and tailorable mechanical properties, suited for innovative technological applications in a variety of modern engineering fields. The paper is focused on analysing the directional auxeticity of tetrachiral materials, through analytical, numerical and experimental methods. Theoretical predictions about the global elastic properties have been successfully validated by performing tensile laboratory tests on tetrachiral samples, realized with high precision 3D printing technologies. Inspired by the kinematic behaviour of the tetrachiral material, a newly-design bi-layered topology, referred to as bi-tetrachiral material, has been theoretically conceived and mechanically modelled. The novel topology virtuously exploits the mutual collaboration between two tetrachiral layers with opposite chiralities. The bi-tetrachiral material has been verified to outperform the tetrachiral material in terms of global Young modulus and, as major achievement, to exhibit a remarkable auxetic behaviour. Specifically, experimental results, confirmed by parametric analytical and computational analyses, have highlighted the effective possibility to attain strongly negative Poisson ratios, identified as a peculiar global elastic property of the novel bi-layered topology.