Large‐Scale Molecular Dynamics Elucidates the Mechanics of Reinforcement in Graphene‐Based Composites

Using very large‐scale classical molecular dynamics, the mechanics of nano‐reinforcement of graphene‐based nanocomposites are examined. Simulations show that significant quantities of large, defect‐free, and predominantly flat graphene flakes are required for successful enhancement of materials properties in excellent agreement with experimental and proposed continuum shear‐lag theories. The critical lengths for enhancement are approximately 500 nm for graphene and 300 nm and for graphene oxide (GO). The reduction of Young's modulus in GO results in a much smaller enhancement of the composite's Young's modulus. The simulations reveal that the flakes should be aligned and planar for optimal reinforcement. Undulations substantially degrade the enhancement of materials properties. The mechanism of reinforcement of polymer materials by graphene‐based inclusions is highly important for the design of high‐performance composites. Very large molecular simulations show that single graphene layers can effectively reinforce the polymer matrix via a shear‐lag process down to flake sizes of 500 nm, as long as the flake is predominantly flat. However, even small undulations of the surface substantially degrade the enhancement of materials properties.