Impact damping and vibration attenuation in nematic liquid crystal elastomers

Mohand O Saed,Andrew Terentjev,Eugene M Terentjev,Dimitrios Chronopoulos,David Williamson,Waiel Elmadih

doi:10.1038/s41467-021-27012-1

Mohand O Saed, Andrew Terentjev + Show 4 more

Open Access

https://doi.org/10.1038/s41467-021-27012-1

Copy DOI

Abstract

Nematic liquid crystal elastomers (LCE) exhibit unique mechanical properties, placing them in a category distinct from other viscoelastic systems. One of their most celebrated properties is the ‘soft elasticity’, leading to a wide plateau of low, nearly-constant stress upon stretching, a characteristically slow stress relaxation, enhanced surface adhesion, and other remarkable effects. The dynamic soft response of LCE to shear deformations leads to the extremely large loss behaviour with the loss factor tanδ approaching unity over a wide temperature and frequency ranges, with clear implications for damping applications. Here we investigate this effect of anomalous damping, optimising the impact and vibration geometries to reach the greatest benefits in vibration isolation and impact damping by accessing internal shear deformation modes. We compare impact energy dissipation in shaped samples and projectiles, with elastic wave transmission and resonance, finding a good correlation between the results of such diverse tests. By comparing with ordinary elastomers used for industrial damping, we demonstrate that the nematic LCE is an exceptional damping material and propose directions that should be explored for further improvements in practical damping applications.

Highlights

Nematic liquid crystal elastomers (LCE) exhibit unique mechanical properties, placing them in a category distinct from other viscoelastic systems
The LCEs are even richer than a nominal Cosserat solid since rubbers are capable of large shear deformations, being at the same time essentially incompressible
We need naturally non-aligned, polydomain LCEs21 with relatively low crosslinking density, which show the wide stress plateau reflecting the elastic softness on nematic director alignment, comparing the basic LCEs with two crosslinking densities: 10% and 40%

Summary

Introduction

Nematic liquid crystal elastomers (LCE) exhibit unique mechanical properties, placing them in a category distinct from other viscoelastic systems. The dynamic soft response of LCE to shear deformations leads to the extremely large loss behaviour with the loss factor tanδ approaching unity over a wide temperature and frequency ranges, with clear implications for damping applications. We investigate this effect of anomalous damping, optimising the impact and vibration geometries to reach the greatest benefits in vibration isolation and impact damping by accessing internal shear deformation modes. Liquid crystalline elastomers (LCEs) are amorphous rubbers with spontaneous orientational order of their anisotropic molecular segments They possess the combination of physical properties that place them in a separate category from any other elastic or viscous material[5]. We compare a range of LCE against current market-leading damping materials, using different testing methods for impact absorption and vibration (elastic) attenuation

Objectives

Methods

Results

Conclusion