A three step recipe for designing auxetic materials on demand

Abstract

Unlike regular elastic materials, when auxetic materials are compressed, they become thinner in the direction perpendicular to the applied force. Despite their outstanding mechanical properties, a systematic design of new and controlled auxetics remains underdeveloped. Here we establish a unified framework to describe bidimensional perfect auxetics with potential use in the design of new materials. Inspired by a natural connection between rotating rigid units and antiferromagnetic spin systems, we unveil the conditions for the emergence of a non-trivial floppy mode responsible for the auxetic behaviour. This model establishes three simple steps to design new auxetics. In particular, we constructed an exotic crystal, a Penrose quasi-crystal and the long-desired isotropic auxetic. The auxeticity of these designs is robust under small structural disturbances, as seen from experiments and numerical simulations. We expect that this work will allow the implementation of auxetic behaviour into advanced materials to enhance their functionalities, with a promising extension into 3D auxetics.

Anomalous linear elasticity of disordered networks

“…Furthermore, we show that the anomalous elasticity for r ≪ ξ features a qualitatively different multipole expansion structure compared to continuum elasticity. These results may have significant implications for long-range mechanical interactions between distant cells through biological extracellular matrices [12], inspire the design of heterogeneous structures with unusual properties [13] and pose new basic questions, which are briefly discussed.…”

How to Create Trusted Tribological Characterization Data of Soft Polymers as Input for FEM Simulations?

“…For isotropic materials, the Poisson's ratios vary between −1 and 0.5 as the corresponding elastic moduli, e.g., Young's modulus, shear modulus, and the compression modulus, must be positive. As auxetic materials [26,27] (ν < 0) with characteristically cellular structures do not provide adequate properties for tribological applications with high contact pressures, the investigated materials are limited here to Poisson's ratios between 0 and 0.5.…”

Auxetics and FEA: Modern Materials Driven by Modern Simulation Methods

“…Other similar studies investigated the mechanical properties and deformation mechanisms of "rotating rigid units"-mimicking systems. Amongst others, Wang et al ( 2021) [170] and Atilla Yolcu et al ( 2022) [171] explored such systems designed through the use of regularly and irregularly peanut-shaped perforations (depicted in Figure 4e); Acuna et al [172] simulated rectangular perforations; whilst Mrozek and Strek [173] (Figure 4f) investigated a system of perforations mimicking the rotating squares model [64,[174][175][176]. Afshar et al utilised FEA to investigate non-porous perforated rotating rigid units having a soft inclusion in the perforations.…”