Graphene Surface Treatment Effects on Mechanical Behavior of Basalt FibersEpoxy Composites

Hypothesis: Polymer matrix composites (PMCs) have various structural applications. To improve the mechanical properties of PMCs, nanoparticles are usually added to polymer matrix as reinforcements to produce polymer matrix nanocomposites. This research investigates the effects of surface treatment of graphene nanoplatelets (GNPs) on the tensile and impact behavior of basalt fibers epoxy composites.
For this purpose, surface treatment of GNPs was performed using (3-aminopropyl) trimethoxysilane. The presence of silicon and nitrogen elements, which are the main components of functionalization group on the surface of treated GNPs, was confirmed by EDX-SEM mapping analysis. The nanocomposites with different weight percentages of treated GNPs (0.2, 0.3, 0.4 and 0.5) were fabricated by hand lay-up method. Also, two composite samples, one without GNPs and the other with 0.4 wt% untreated GNPs were fabricated to compare with those reinforced with treated GNPs. Tensile and Charpy impact tests were performed on fully cured samples.
Findings: The results showed 21.1, 3.6, 35.1 and 74.6 percent increase in tensile strength, modulus of elasticity, fracture energy and impact strength, in the order given, for nanocomposites reinforced with 0.4 wt% treated GNPs were obtained compared to those without GNPs. Also, 52.1, 37.5, 57.9 and 25.5 percent decrease in properties, in the stated order, were observed for nanocomposites with 0.4 wt% of untreated GNPs compared to those without GNPs. According to the SEM images, the increase in tensile properties could be related to the improvement in the adhesion between basalt fibers and epoxy resin, and also the toughening mechanism of treated GNPs. The surface treatment increased the interaction between the GNPs and the matrix, and also the presence of treated GNPs promoted crack deflection phenomenon that is one of the major toughening mechanisms of GNPs. The reduction in the mechanical properties of sample containing 0.4 wt% untreated GNPs was attributed to the uneven dispersion of GNPs in the epoxy matrix and the weak interactions between the graphene nanoplatelets and matrix and fiber.