| Fiber reinforced polymer (FRP) composites have exceptional advantage over traditional materials for their lightweight, high stiffness and strength, high resistance to corrosion and fatigue, which results in lower total life time cost. A primary limitation of FRP in aircraft applications is susceptibility to lightning because of poor electrical, thermal and electromagnetic properties. The current methods to mitigate the lightning strike in aircraft have added weight and reduced the performance. A number of explorations are being made to improve electrical, thermal and electromagnetic properties by nanofillers, such as carbon nanotube, graphene etc. Graphene is found to offer vapor barrier properties to composite because of its platelet structure. Therefore, this research is focused on graphene/epoxy nanocomposites.;First step of this research was to develop processing method for graphene/epoxy nanocomposites. Then, this research expands to the fabrication of carbon fiber reinforced nanocomposites. The fundamental criteria used for process development was electrical conductivity, process repeatability and scale up to a larger batch of material. The materials chosen in this study are graphene nanoplatelets (xGnP-25), epon 828 epoxy resin and woven carbon fiber as reinforcement. Three types of exfoliation and dispersion techniques were investigated: conventional mechanical mixing, sonication and three-roll mill. The study showed that three-roll mill dispersion is most repeatable, consistent and scalable to larger batches. The optimized process consists of three gap settings (40, 30 and 25 microm) at 200 rpm and three passes for each gap setting. The percolation thereshold of xGnP graphene in epon 828 epoxy was found to be 1.0 wt. %. The xGnP/epon 828 nanocomposites showed an increase of eight log cycles in electrical conductivity, 93 % in thermal conductivity and 34 % in fracture toughness over the base epon 828. Carbon/xGnP/epon 828 fiber reinforced composite panels were fabricated by compression molding technique. The electrical, thermal and mechanical properties of nanocomposites were compared with base composite and found that electrical conductivity doubled while all other properties remained practically same. |
