Mechanical properties of graphene nanoplatelet/epoxy composites

Because of their high-specific stiffness, carbon-filled epoxy composites can be used in structural components in fixed-wing aircraft. Graphene nanoplatelets (GNPs) are short stacks of individual layers of graphite that are a newly developed, lower cost material that often increases the composite tensile modulus. In this work, researchers fabricated neat epoxy (EPON 862 with Curing Agent W) and 16 wt % GNP in epoxy composites. The cure cycle used for this aerospace epoxy resin was 2 h at 121 degrees C followed by 2 h at 177 degrees C. These materials were tested for tensile properties using typical macroscopic measurements. Nanoindentation was also used to determine modulus and creep compliance. These macroscopic results showed that the tensile modulus increased from 2.72 GPa for the neat epoxy to 3.36 GPa for 6 wt % (3.7 vol %) GNP in epoxy composite. The modulus results from nanoindentation followed this same trend. For loadings from 10 to 45 mN, the creep compliance for the neat epoxy and GNP/epoxy composites was similar. The GNP aspect ratio in the composite samples was confirmed to be similar to that of the as-received material by using the percolation threshold measured from electrical resistivity measurements. Using this GNP aspect ratio, the two-dimensional randomly oriented filler HalpinTsai model adjusted for platelet filler shape predicts the tensile modulus well for the GNP/epoxy composites. Per the authors' knowledge, mechanical properties and modeling for this GNP/epoxy system have never been reported in the open literature. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013