Role of electrochemically in-house synthesized and functionalized graphene nanofillers in the structural performance of epoxy matrix composites.

The present study focuses on the intriguing enhancement in the mechanical properties of an epoxy-based composite structure resulting from the incorporation of in-house synthesized functionalized graphene nanosheets (f-GNSs) as nanofillers. The f-GNSs were obtained by anionic electrochemical intercalation and exfoliation with 2 M H2 SO4 , HClO4 , and HNO3 protic electrolytes. The structural properties of the as-synthesized GNSs were analyzed by XRD and Raman spectroscopy. The (002) and (001) lattice planes of graphene and graphene oxide are observed at around 24.5° and 11° (2θ), respectively, in the XRD spectra. The characteristic peaks at around 1345, 1590, and 2700 cm-1 correspond to the D, G, and 2D bands of the GNSs in the Raman spectra. Quantification of the functional groups and sp2 contents in the GNSs were further analyzed by XPS. Morphological characterization of the f-GNSs reveals that the exfoliated carbon sheets consist of 2-8 layers. The composites are then fabricated by addition of these f-GNSs nanofillers, and the effect of the wt% of the nanofillers on the mechanical properties of the composites is analyzed with the three-point bend test and fractography analysis through interfacial morphological analysis. The addition of 0.1 wt% of nitric-acid-exfoliated f-GNSs nanofiller results in maximum increases of 42.6% and 28.2% in the flexural strengths of neat epoxy resin and glass fiber/epoxy polymer composite structures, respectively. Similarly, the moduli increase by 33.5% and 57.7% in the neat epoxy resin and glass fiber/epoxy polymer composite structures, respectively. The effect of epoxy/f-GNSs interfacial bonding in the composite structure was studied by DSC analysis.