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Apparent negative values of Young's moduli of lattice materials under dynamic conditions

Apparent negative values of Young's moduli of lattice materials under dynamic conditions
Apparent negative values of Young's moduli of lattice materials under dynamic conditions

Lattice materials are characterised by their equivalent elastic moduli for analysing mechanical properties of the microstructures. The values of the elastic moduli under static forcing condition are primarily dependent on the geometric properties of the constituent unit cell and the mechanical properties of the intrinsic material. Under a static forcing condition, the equivalent elastic moduli (such as Young's modulus) are always positive. When dynamic forcing is considered, the equivalent elastic moduli become functions of the applied frequency and they can be negative at certain frequency values. This paper, for the first time, explicitly demonstrates the occurrence of negative equivalent Young's modulus in lattice materials experimentally. Using additively manufactured titanium-alloy lattice metastructures, it is shown that the real part of experimentally measured in-plane Young's modulus becomes negative under a dynamic environment. In fact, we show that the onset of such negative Young's modulus in lattice materials can be precisely determined by capturing the sub-wavelength scale dynamics of the system. Experimental confirmation of the negative Young's moduli and the onset of the same as a function of frequency provide the necessary physical insights and confidence for its potential exploitation in various multi-functional structural systems and devices across different length scales.

Dynamic analysis of honeycomb, Dynamics of additively manufactured lattice, Frequency-dependent elastic property, Lattice material, Negative Young's modulus, Onset of negative elastic moduli
0020-7225
Adhikari, S.
82960baf-916c-496e-aa85-fc7de09a1626
Mukhopadhyay, T.
2ae18ab0-7477-40ac-ae22-76face7be475
Shaw, A.
61611d8c-53d4-4445-b2e1-1bad95bca35b
Lavery, N. P.
2d119501-ba10-4814-af2d-4f17f18b9ef9
Adhikari, S.
82960baf-916c-496e-aa85-fc7de09a1626
Mukhopadhyay, T.
2ae18ab0-7477-40ac-ae22-76face7be475
Shaw, A.
61611d8c-53d4-4445-b2e1-1bad95bca35b
Lavery, N. P.
2d119501-ba10-4814-af2d-4f17f18b9ef9

Adhikari, S., Mukhopadhyay, T., Shaw, A. and Lavery, N. P. (2020) Apparent negative values of Young's moduli of lattice materials under dynamic conditions. International Journal of Engineering Science, 150, [103231]. (doi:10.1016/j.ijengsci.2020.103231).

Record type: Article

Abstract

Lattice materials are characterised by their equivalent elastic moduli for analysing mechanical properties of the microstructures. The values of the elastic moduli under static forcing condition are primarily dependent on the geometric properties of the constituent unit cell and the mechanical properties of the intrinsic material. Under a static forcing condition, the equivalent elastic moduli (such as Young's modulus) are always positive. When dynamic forcing is considered, the equivalent elastic moduli become functions of the applied frequency and they can be negative at certain frequency values. This paper, for the first time, explicitly demonstrates the occurrence of negative equivalent Young's modulus in lattice materials experimentally. Using additively manufactured titanium-alloy lattice metastructures, it is shown that the real part of experimentally measured in-plane Young's modulus becomes negative under a dynamic environment. In fact, we show that the onset of such negative Young's modulus in lattice materials can be precisely determined by capturing the sub-wavelength scale dynamics of the system. Experimental confirmation of the negative Young's moduli and the onset of the same as a function of frequency provide the necessary physical insights and confidence for its potential exploitation in various multi-functional structural systems and devices across different length scales.

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More information

Published date: May 2020
Additional Information: Publisher Copyright: © 2020 Elsevier Ltd
Keywords: Dynamic analysis of honeycomb, Dynamics of additively manufactured lattice, Frequency-dependent elastic property, Lattice material, Negative Young's modulus, Onset of negative elastic moduli

Identifiers

Local EPrints ID: 483567
URI: http://eprints.soton.ac.uk/id/eprint/483567
ISSN: 0020-7225
PURE UUID: 4915a7fc-efbb-4f17-942d-0b19940a4d17
ORCID for T. Mukhopadhyay: ORCID iD orcid.org/0000-0002-0778-6515

Catalogue record

Date deposited: 01 Nov 2023 18:01
Last modified: 06 Jun 2024 02:16

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Contributors

Author: S. Adhikari
Author: T. Mukhopadhyay ORCID iD
Author: A. Shaw
Author: N. P. Lavery

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