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Exploiting nonlinearities through geometric engineering to enhance the auxetic behaviour in re-entrant honeycomb metamaterials

Srivastava, C and Bhola, L and Mahesh, V and Guruprasad, PJ and Petrinic, N and Scarpa, F and Harursampath, D and Ponnusami, SA (2023) Exploiting nonlinearities through geometric engineering to enhance the auxetic behaviour in re-entrant honeycomb metamaterials. In: Scientific Reports, 13 (1).

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Official URL: https://doi.org/10.1038/s41598-023-47525-7


Classical approaches to enhance auxeticity quite often involve exploring or designing newer architectures. In this work, simple geometrical features at the member level are engineered to exploit non-classical nonlinearities and improve the auxetic behaviour. The structural elements of the auxetic unit cell are here represented by thin strip-like beams, or thin-walled tubular beams. The resulting nonlinear stiffness enhances the auxeticity of the lattices, especially under large deformations. To quantify the influence of the proposed structural features on the resulting Poisson�s ratio, we use here variational asymptotic method (VAM) and geometrically exact beam theory. The numerical examples reveal that 2D re-entrant type micro-structures made of thin strips exhibit an improvement in terms of auxetic behaviour under compression. For the auxetic unit cell with thin circular tubes as members, Brazier�s effect associated with cross-sectional ovalisation improves the auxetic behaviour under tension; the enhancement is even more significant for the 3D re-entrant geometry. Thin strip-based auxetic unit cells were additively manufactured and tested under compression to verify the numerical observations. The experimentally measured values of the negative Poisson�s ratio are in close agreement with the numerical results, revealing a 66 increase due to the nonlinearity. Simulation results showcase these alternative approaches to improve the auxetic behaviour through simple geometric engineering of the lattice ribs. © 2023, The Author(s).

Item Type: Journal Article
Publication: Scientific Reports
Publisher: Nature Research
Additional Information: The copyright for this article belongs to author.
Keywords: article; compression; controlled study; geometry; nonlinear system; rigidity; simulation
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Date Deposited: 29 Feb 2024 05:57
Last Modified: 29 Feb 2024 05:57
URI: https://eprints.iisc.ac.in/id/eprint/83732

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