Exploring the dynamics of hourglass shaped lattice metastructures

Vivek Gupta,Sondipon Adhikari,Bishakh Bhattacharya

doi:10.1038/s41598-020-77226-4

Vivek Gupta, Sondipon Adhikari + Show 1 more

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https://doi.org/10.1038/s41598-020-77226-4

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Abstract

Continuous demand for the improvement of mechanical performance of engineering structures pushes the need for metastructures to fulfil multiple functions. Extensive work on lattice-based metastructure has shown their ability to manipulate wave propagation and producing bandgaps at specific frequency ranges. Enhanced customizability makes them ideal candidates for multifunctional applications. This paper explores a wide range of nonlinear mechanical behavior that can be generated out of the same lattice material by changing the building block into dome shaped structures which improves the functionality of material significantly. We propose a novel hourglass shaped lattice metastructure that takes advantage of the combination of two oppositely oriented coaxial domes, providing an opportunity for higher customizability and the ability to tailor its dynamic response. Six new classes of hourglass shaped lattice metastructures have been developed through combinations of solid shells, regular honeycomb lattices and auxetic lattices. Numerical simulation, analytical modelling, additive layer manufacturing (3D printing) and experimental testing are implemented to justify the evaluation of their mechanics and reveal the underlying physics responsible for their unusual nonlinear behaviour. We further obtained the lattice dependent frequency response and damping offered by the various classes of hourglass metastructures. This study paves the way for incorporating hourglass based oscillators to be used as building block of future mechanical metamaterials, leading to a new class of tunable metamaterial over a wide range of operating frequencies. The proposed class of metastructure will be useful in applications where lightweight and tunable properties with broadband vibration suppression and wave attenuation abilities are necessary.

Highlights

Continuous demand for the improvement of mechanical performance of engineering structures pushes the need for metastructures to fulfil multiple functions
Unlike the traditional phononic crystals, whose bandgap behavior gets fixed with the patterning of the structural building blocks, the properties of metamaterials are adjustable due to tunability of the local structural resonances of individual elements in the unit c ell[4,5]
Since most of the existing metamaterials operate in a narrow band, there is a significant interest in developing tunable metamaterials, which allow for adjustable operating frequencies and have greater potential in acoustic imaging6, cloaking[7] and protection of civil infrastructures from impact and seismic threats[8,9,10]

Summary

Introduction

Continuous demand for the improvement of mechanical performance of engineering structures pushes the need for metastructures to fulfil multiple functions. Various alterations of periodic arrangements were explored, ranging from a lumped mass model of a 1D metastructure[11] to cycloidal resonators and an array of cylindrical r esonator[15,16] All these metastructure designs have a limited scope of tunability due to the relatively simple geometry of building blocks. The lattice based architected metastructures have shown enhanced static properties as well as the ability to control wave propagation, making them ideal for multifunctional applications[17,18,19] They opened up new areas of the tunable material property set. Auxetic based domes show reduced snap-through in comparison with conventional lattices and solid d ome[34]

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