Soft-Elasticity Optimises Dissipation in 3D-Printed Liquid Crystal Elastomers

TL;DR

This study demonstrates 3D-printed monodomain liquid crystal elastomers with soft-elasticity that effectively dissipate impact energy across a wide range of strain rates, offering promising impact-absorbing applications.

Contribution

First successful 3D printing of bulk monodomain LCEs and comprehensive analysis of their impact-absorbing properties across various strain rates.

Findings

Monodomain LCE dissipates 45% of strain energy at quasi-static rates.

LCE performs closest to an ideal impact absorber at high strain rates up to 3000 s^{-1}.

Drop tests show a 40% reduction in impact severity compared to isotropic elastomers.

Abstract

Soft-elasticity in monodomain liquid crystal elastomers (LCEs) is promising for impact-absorbing applications where strain energy is ideally absorbed at constant stress. Conventionally, compressive and impact studies on LCEs have not been performed given the notorious difficulty synthesizing sufficiently large monodomain devices. Here we demonstrate 3D printing bulk ($>cm^3$) monodomain LCE devices using direct ink writing and study their compressive soft-elasticity over 8 decades of strain rate. At quasi-static rates, the monodomain soft-elastic LCE dissipated 45% of strain energy while comparator materials dissipated less than 20%. At strain rates up to $3000~s^{-1}$, our soft-elastic monodomain LCE consistently performed closest to an ideal-impact absorber. Drop testing reveals soft-elasticity as a likely mechanism for effectively reducing the severity of impacts -- with soft elastic LCEs offering a Gadd Severity Index 40% lower than a comparable isotropic elastomer. Lastly, we demonstrate tailoring deformation and buckling behavior in monodomain LCEs via the printed director orientation.