Negative In-plane Elastic Moduli of Metallic Lattices: Experimental Investigations

Adhikari, Sondipon, Shaw, Alex, Mukhopadhyay, Tanmoy and Lavery, Nicholas P. (2019) Negative In-plane Elastic Moduli of Metallic Lattices: Experimental Investigations. 10th International Conference on Metamaterials, Photonic Crystals and Plasmonics, META 2019, , Lisbon, Portugal. 23 - 26 Jul 2019. pp. 1599-1600 .

Abstract

In plane elastic moduli of lattice mechanical metamaterials include elastic moduli in the X and Y directions and a shear modulus. Historically, these moduli were described by positive real values considering the deformation of the material under a static stress field. When dynamic behavior of lattice metamaterials are considered, it is possible to express elastic moduli as functions of frequency. In this case, it is first theoretically shown that there exist a critical frequency beyond which the elastic moduli become negative. The analysis is based on a dynamic equilibrium of a unit cell. Experimental investigations involve dynamic testing of a hexagonal lattice made of a titanium alloy. Theoretical predictions of equivalent elastic moduli and negative frequency values are validated with experimental results.

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