Impact damping in hybrid liquid-crystalline elastomer metamaterials

Liquid-crystalline elastomers (LCEs) exhibit anomalously high mechanical damping in the nematic phase, arising from coupling between elastic deformation and orientational relaxation. However, their use in impact protection is limited by the low restoring force associated with soft-elastic deformation and by the poor structural stability of bulk soft elastomers under severe loading. Here we investigate hybrid LCE metamaterials in which a thermoplastic polyurethane scaffold provides mechanical reinforcement while the LCE phase remains the primary dissipative medium. Two LCE compositions, differing in crosslink density, were incorporated into thin 2D honeycomb and thicker 3D diamond scaffold architectures. Tensile and compression tests show that scaffolding strongly increases mechanical stability without eliminating large-strain deformability. Impulse-calibrated drop-impact measurements show that both scaffolded architectures retain the broad, attenuated force pulses characteristic of nematic LCE damping, despite their higher stiffness. This preservation of damping is lost when the LCE is heated into the isotropic phase, confirming the essential role of nematic orientational dissipation. Under high-energy impact, 3D diamond LCE metamaterials remain mechanically coherent, whereas isotropic elastomeric controls fail catastrophically. These results show that internal scaffolding can stabilise and reinforce LCEs without suppressing their anomalous impact-damping response, providing a design route to soft metamaterials that combine load-bearing integrity with molecularly enabled energy dissipation.