In this study, graphene nanoplatelets (GNPs) added to epoxy matrix composite reinforced by aeronautical grade carbon fibers (CFs) were fabricated by the vacuum infusion method, and the effect of different GNPs contents (0.05, 0.25, and 1.25 wt%) on electrical conductivity, flexural properties, and dynamic mechanical properties were investigated. The results revealed an 8-and 73-times improvement in conductivity values across the thickness with the addition of 0.05 and 0.25 wt% GNPs, respectively, compared to the neat composite. Flexural test results showed that with the addition of 0.05 GNP, only 6% increase in flexural strength was obtained, while with the addition of 0.25 wt% GNP flexural strength remained almost the same as for the neat composite. On the contrary, the addition of GNPs (1.25% by weight) causes a reduction in the flexural strength with respect to the neat composite. This was confirmed by the fractured surfaces examined by scanning electron microscope which reveals that considerable amount of fiber-matrix debonding was observed with 1.25 GNPs loading. Dynamic mechanical analysis (DMA) revealed that the storage modulus of the neat composite increased by 12.6% with the addition of only a small amount of GNP (0.05% wt) compared to the neat composite. Composite with 1.25 GNP shows upward bending, affecting the shape of the cole-cole plot obtained from DMA results, indicating inappropriate interactions of GNPs in both the matrix and CF in the composite.

The electrical and mechanical properties of carbon fiber-reinforced polymer (CFRP) composites have a close dependence on the use of modifiers like polyvinylpyrrolidone (PVP), as well as on the processing techniques to disperse functional charges such as graphene-related materials into the epoxy base. In the present work, reduced graphene oxide (RGO), prepared by a natural antioxidant agent, astaxanthin, was used as a filler material in the epoxy matrix of the carbon fiber composites. The astaxanthin reduction leads to an increase in the sp2 ordering in RGO; some residual epoxy and C-O groups that enhance the interaction with the epoxy matrix remain after reduction. The effects of RGO and PVP-modified RGO (PVP-RGO) fillers with different contents (0.05, 0.1, and 0.15% wt.) on the electrical conductivity, bending properties, and dynamic mechanical properties of CFRP were investigated. The incorporation of 0.15 wt.% RGO with and without PVP-modification, leads to through-the-thickness (Z-direction testing) conductivity values 7.4 and 9.6 times higher than those of the neat composite, respectively. The conductivity tests indicate that the RGO/epoxy composite behaves as a continuous conductor due to the formation of agglomerates of RGO within the matrix, while at the added contents of the PVP-RGO filler, the composite is below the percolation threshold, then conducting by electron tunneling, due to a better dispersion of the PVP-RGO filler within the epoxy matrix. The dynamic mechanical analysis shows that the glass transition temperature is indicative of the interactions among the filler, the epoxy matrix, and the carbon fiber, that is, the PVP-RGO filler increases the chain mobility due to its higher dispersion in the matrix. While Tg of the neat epoxy/CFRP composite is 92.5°C, a minimum Tg of 88.5°C was achieved with a 0.10 % wt. PVP-RGO filler contents, and a maximum Tg of 94.5°C with a 0.15 % wt. of RGO filler amount. For constant filler content (0.15 wt.%), CFRP composite containing RGO and PVP-modified RGO exhibited 9.73% and 13.87% increase in flexural strength values, respectively, compared to the neat composite. The bending test revealed that PVP modification to RGO is beneficial to improve flexural strength of CFRP composites.

Graphene oxide, as a nanoscopic platform for functional materials, has been extensively studied for several applications. The present Mini Review stresses the collaborative research in graphene-oxide materials pivoted from the Group of Materials and Technologies for Energy, Health, and Environment at an Instituto Politecnico Nacional unit in Tamaulipas, in Northeastern Mexico, with Mexican, Turkish, and British collaborators. This review covers the recent works on photovoltaic and photocatalytic materials, coatings for thermonuclear reactors, and composites and metamaterials for military and aeronautic applications.