Effects of functionalized graphene nanoplatelets on the flexural behaviors of basalt fibers/epoxy composites

The effects of functionalized graphene nanoplatelets (FGN) on the flexural properties of basalt fibers/epoxy composites were studied. The functionalization of graphene was performed by 3-Aminopropyltrimethoxysilane. Four nanocomposites with different weight percentages of FGN (0.2, 0.3, 0.4 and 0.5) were fabricated via hand lay-up method. Among these four, the nanocomposite reinforced by 0.4 wt.% FGN showed the best flexural behavior. To investigate the effects of graphene as well as its functionalization, two other composites one without graphene and another reinforced by 0.4 wt.% of unfunctionalized graphene nanoplatelets (UFGN) were also fabricated. In comparison to the sample without graphene, the nanocomposite with 0.4 wt.% of FGN showed respectively 89.6, 252.6 and 44.6 percent improvements in the flexural strength, flexural modulus and fracture energy, but the nanocomposite with 0.4 wt.% UFGN showed respectively 26.2 and 10.8 percent decrease in the flexural strength and fracture energy, although had a slight increase of 3.1 percent in the flexural modulus. These results indicated that functionalization facilitated the dispersion of graphene in the matrix and thus enhanced its interaction to both matrix and basalt fibers. According to the Fourier transform infrared spectroscopy results, the improvement in the flexural properties is related to the functional groups whose presence on the graphene platelets enhanced better adherence to the polymer’s molecules and the basalt fibers. Furthermore, scanning electron microscopy observations of the fracture surfaces showed better polymer to fiber interfacial adhesion and thus caused toughening mechanisms such as crack deflection, graphene delamination and crack pining in the FGN containing samples.