Development of graphene and boron nitride reinforced carbon fabric epoxy hybrid composites for aviation applications

Materials used in aerospace applications must be lightweight, as their weight significantly affects the flight speed, range, and fuel consumption of aircraft and rockets. In addition to being lightweight, these materials are also required to exhibit advanced mechanical properties. Due to their low density and superior mechanical performance, fiber-reinforced polymer matrix composites are widely preferred in these fields. In such composites, fibers can be used alone as reinforcement elements, or various nanofillers (e.g., carbon nanotubes, graphene and its derivatives, ceramic and metal-based materials, boron nitride, etc.) can be incorporated to enhance mechanical and other functional properties (e.g., thermal and electrical conductivity). This study aims to investigate the effects of boron nitride and graphene nanofillers, used separately and in hybrid form at different weight fractions (0.25%, 0.5%, and 1.0%), on the mechanical properties of carbon fiber-reinforced epoxy matrix composites. First, the nanomaterials were homogeneously dispersed within the epoxy matrix, and composites were produced using a vacuum infusion method. The manufactured composites were then cut according to ASTM standards and subjected to flexural, tensile, and impact tests. The highest flexural and tensile strengths in graphene- and boron nitride-reinforced composites were observed in samples (G2 and B2) containing 0.5% nanofillers. Compared to unreinforced reference sample (N), the G2 sample exhibited 10.5% and 7.76% higher flexural and tensile strengths, respectively, while the B2 sample showed 8.48% and 10.41% higher values, respectively. In the hybrid nanofiller (graphene + boron nitride) composites, the H1 sample with 0.25% filler content demonstrated 15.47% and 7.17% higher flexural and tensile strengths than the reference sample. Furthermore, it was observed that the addition of nanofillers to the epoxy matrix improved the impact strength of the composites. The G3, B2, and H3 samples exhibited impact resistance values of 72.89 kJ/m², 66.32 kJ/m², and 70.15 kJ/m², respectively, which are 27.92%, 16.39%, and 23.11% higher than that of the reference sample. After mechanical testing, the fracture surfaces of the composites were examined using scanning electron microscopy (SEM), revealing failure mechanisms such as fiber breakage, fiber pull-out, and matrix cracking.