Bio-inspired self-folding strategy to break the trade-off between strength and ductility in carbon-nanoarchitected materials

XZ Jia and Z Liu and EL Gao, NPJ COMPUTATIONAL MATERIALS, 6, 13 (2020).

DOI: 10.1038/s41524-020-0279-8

Graphene possesses extraordinary mechanical, electronic, and thermal properties, thus making it one of the most promising building blocks for constructing macroscopic high performance and multifunctional materials. However, the common material strength-ductility paradox also appears in the carbon-nanoarchitected materials and some of the key mechanical performance, for example, the tensile strength of graphene-based materials, are still far lower than that of graphene. Inspired by the exceptional mechanical performance of silk protein benefiting from the conformations of folded structures as well as their transitions, this work proposed a topological strategy to yield graphene-based materials with ultrahigh ductility while maintaining decent tensile strength by self-folding graphene sheets. This drastically improved mechanical performance of graphene-based materials is attributed to the exploitation of shearing, sliding, and unfolding deformation at the self-folded interface. Molecular dynamics simulations show that both modulating self-folded length and engineering interface interaction can effectively control the strength, ductility, and the ductile failure of van der Waals interfaces among the self-folded structures, where interfacial shearing, sliding, and unfolding open channels to dissipate mechanical energy. Based on the insights into the atomic-scale deformation by molecular dynamics simulations, the underlying mechanism of deformation and failure of these materials is finally discussed with a continuum mechanics-based model. Our findings bring perceptive insights into the microstructure design of strong-yet-ductile materials for load-bearing engineering applications.

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