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

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 H₂SO₄, 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.