Flexible planar metamaterials with tunable Poisson's ratios

This research reports on the design, fabrication, and multiscale mechanical characterization of flexible, planar mechanical metamaterials with tailorable mechanical properties. The tunable mechanical behavior of the structures is realized through the introduction of orthogonal perforations with different geometric features. Various configurations of the perforations lead to a wide range of Poisson's ratios (from-0.8 to 0.4), load-bearing properties, and energy absorption capacities. The correlations between the configuration of the perforations and the auxetic response of the structures are highlighted through computational and experimental characterizations performed at multiple length scales. It is demon-strated that the local in-plane rotation of the solid ligaments in a uniaxially loaded structure is the pri-mary factor that contributes to its strain-dependent auxetic behavior at macroscopic scales. Confinement of these local rotations is then used as a practical strategy to activate a self-strengthening mechanism in the auxetic structures. It is further shown that the fabrication of planar flexible structures with control-lable Poisson's ratios is feasible through spatial adjustment of perforations in the structure. Finally, dis-cussions are provided regarding the practical applications of these structures for a new generation of highly energy-absorbing protective equipment. (c) 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This research focuses on the design, fabrication, and mechanical characterization of flexible, planar mechanical metamaterials with tunable properties. By introducing different geometric perforations, the structures exhibit adjustable mechanical behavior and a wide range of Poisson's ratios. The study highlights the correlation between perforation configurations and auxetic response, and proposes a practical strategy for activating a self-strengthening mechanism in the structures. It also demonstrates the feasibility of fabricating planar flexible structures with controllable Poisson's ratios through spatial adjustment of perforations.