Double-network-inspired mechanical metamaterials

TL;DR

This paper introduces double-network-inspired metamaterials that combine stiff and compliant components to achieve significantly enhanced stiffness and stretchability, inspired by polymer network structures.

Contribution

It presents a novel metamaterial architecture inspired by double-network hydrogels, achieving tenfold improvements in mechanical properties and elucidating energy dissipation mechanisms.

Findings

Achieved tenfold increase in stiffness and stretchability.

Enhanced energy dissipation through network entanglements.

Internal defects lead to threefold increase in energy dissipation.

Abstract

Mechanical metamaterials are renowned for their ability to achieve high stiffness and strength at low densities, often at the expense of low ductility and stretchability-a persistent trade-off in materials. In contrast, materials such as double-network hydrogels feature interpenetrating compliant and stiff polymer networks, and exhibit unprecedented combinations of high stiffness and stretchability, resulting in exceptional toughness. Here, we present double-network-inspired (DNI) metamaterials by integrating monolithic truss (stiff) and woven (compliant) components into a metamaterial architecture, which achieve a tenfold increase in stiffness and stretchability compared to their pure woven and truss counterparts, respectively. Nonlinear computational mechanics models elucidate that enhanced energy dissipation in these DNI metamaterials stems from increased frictional dissipation due to entanglements between the two networks. Through introduction of internal defects, which typically degrade mechanical properties, we demonstrate an opposite effect of a threefold increase in energy dissipation for these metamaterials via failure delocalization. This work opens avenues for developing new classes of metamaterials in a high-compliance regime inspired by polymer network topologies.