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A Novel Mechanical Metamaterial Exhibiting Auxetic Behavior and Negative Compressibility.

ABSTRACT: Auxetics (negative Poisson's ratio) and materials with negative linear compressibility (NLC) exhibit the anomalous mechanical properties of getting wider rather than thinner when stretched and expanding in at least one direction under hydrostatic pressure, respectively. A novel mechanism-termed the 'triangular elongation mechanism'-leading to such anomalous behavior is presented and discussed through an analytical model. Amongst other things, it is shown that this novel mechanism, when combined with the well-known 'rotating squares' model, can generate giant negative Poisson's ratios when the system is stretched.

SUBMITTER: Grima-Cornish JN

PROVIDER: S-EPMC6982174 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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A Novel Mechanical Metamaterial Exhibiting Auxetic Behavior and Negative Compressibility.

Grima-Cornish James N JN Grima Joseph N JN Attard Daphne D

Materials (Basel, Switzerland) 20191222 1

Auxetics (negative Poisson's ratio) and materials with negative linear compressibility (NLC) exhibit the anomalous mechanical properties of getting wider rather than thinner when stretched and expanding in at least one direction under hydrostatic pressure, respectively. A novel mechanism-termed the 'triangular elongation mechanism'-leading to such anomalous behavior is presented and discussed through an analytical model. Amongst other things, it is shown that this novel mechanism, when combined ...[more]

PMID: 31877886

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Project description:Mechanical metamaterials are man-made rationally-designed structures that present unprecedented mechanical properties not found in nature. One of the most well-known mechanical metamaterials is auxetics, which demonstrates negative Poisson's ratio (NPR) behavior that is very beneficial in several industrial applications. In this study, a specific type of auxetic metamaterial structure namely idealized 3D re-entrant structure is studied analytically, numerically, and experimentally. The noted structure is constructed of three types of struts-one loaded purely axially and two loaded simultaneously flexurally and axially, which are inclined and are spatially defined by angles θ and φ. Analytical relationships for elastic modulus, yield stress, and Poisson's ratio of the 3D re-entrant unit cell are derived based on two well-known beam theories namely Euler-Bernoulli and Timoshenko. Moreover, two finite element approaches one based on beam elements and one based on volumetric elements are implemented. Furthermore, several specimens are additively manufactured (3D printed) and tested under compression. The analytical results had good agreement with the experimental results on the one hand and the volumetric finite element model results on the other hand. Moreover, the effect of various geometrical parameters on the mechanical properties of the structure was studied, and the results demonstrated that angle θ (related to tension-dominated struts) has the highest influence on the sign of Poisson's ratio and its extent, while angle φ (related to compression-dominated struts) has the lowest influence on the Poisson's ratio. Nevertheless, the compression-dominated struts (defined by angle φ) provide strength and stiffness for the structure. The results also demonstrated that the structure could have zero Poisson's ratio for a specific range of θ and φ angles. Finally, a lightened 3D re-entrant structure is introduced, and its results are compared to those of the idealized 3D re-entrant structure.

Dataset Information

A Novel Mechanical Metamaterial Exhibiting Auxetic Behavior and Negative Compressibility.

Publications

A Novel Mechanical Metamaterial Exhibiting Auxetic Behavior and Negative Compressibility.

Similar Datasets

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