Effect of graphene dispersion on the equilibrium structure and deformation of graphene/eicosane composites as surrogates for graphene/polyethylene composites: a molecular dynamics simulation

Molecular dynamics simulations are used to investigate the effect of graphene dispersion on the equilibrium structure and deformation of graphene/eicosane composites. Two graphene sheets with four different interlayer distances are incorporated, respectively, into a eicosane matrix to form graphene/eicosane composites representing different graphene dispersions. With greater graphene dispersion, the “adsorption solidification” of the eicosane increases, where eicosane molecular lamination, orientation, and extension become more uniform and stronger. In addition, eicosane molecular motion is inhibited more in the direction perpendicular to graphene surfaces. When these graphene/eicosane composites are deformed, the free volume initially increases slowly due to small, scattered voids. After reaching the yield strains, the free volume rises sharply as the structures of composites are damaged, and small voids merge into large voids. The damage always occurs in the region of the composite with the weakest “adsorption solidification.” Since this effect is stronger when the graphene sheets are more dispersed, more complete dispersion results in higher composite yield stresses. Lessons from these simulations may provide some insights into graphene/polyethylene composites, where suitable models would require very long equilibration times.