Flaw-Tolerant Graphene Oxide-Polymer Nanocomposites through Bio-Inspired Stiffness Modulation
Synthetic nanocomposites using carbon nanostructures such as carbon nanotubes, graphene, or graphene oxide as the load-bearing units within a polymer matrix are promising structural materials due to their potential for high strength and stiffness. However, the mechanical properties of these macroscale composites are presently limited by many types of flaws and relatively weak interfaces, preventing them from achieving high strengths comparable to their parent nanostructures. Because these carbon-based nanofillers comprise of particles that are non-uniform in composition, structures, and morphologies, and their distribution within a composite are difficult to control, we choose to fabricate nanocomposites that are flaw-tolerant, rather than flawless. In this talk, we describe the fabrication, mechanical measurements, and structure-property relationships of multilayer graphene oxide-polymer composite films with alternating soft, crack-hindering polymer layers and stiff, load-bearing graphene oxide layers. This structure is inspired by that of sponge spicules, where periodic lamellae of soft protein and hard mineral hinder crack propagation, increasing strength and toughness[2,3]. We find multilayer films fabricated in this fashion have double the strength of pure graphene oxide films without sacrificing stiffness, and that employing an optimal polymer layer thickness can maximize both stiffness and strength. Finite-element analysis of the multilayer film reveals the stress redistribution that occurs around a broken graphene oxide layer, providing insights into the statistical nature of the strengths of these multilayer films. This work was supported by the ARO MURI (Award # W991NF-09-1-0541).
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