Study on electrical degradation, processing and interfacial strength of carbon fiber epoxy composites with polymers and fillers

Abstract

The electric current induced damages in carbon fiber composites necessitates an improvement in their electric and thermal properties. The study investigates the effect of graphene as a filler material in carbon fiber epoxy composites with regards to their electrical, mechanical, and viscoelastic properties. Cross ply carbon fiber laminates with epoxy and epoxy loaded with three different concentrations of graphene (0.7, 1.4 and 2.8 wt. % of epoxy) are fabricated by hand layup technique. The specimens are subjected to a constant current density of 46 kA/m² for 3 hours and the variation in resistance and temperature are monitored real-time. Dynamic mechanical analysis (DMA), combined loading compression testing (CLC), three-point bend test, transverse and through thickness resistivity measurements are performed after electrical degradation. To differentiate the effect of thermal and electrothermal behavior, a few samples in each case are exposed to isothermal conditions. It is noticed that the addition of graphene led to a significant decrease in resistance (17-49 %) and temperature (17-39 %) of the specimen when electric current is passed through them. A 9-25 % increase in Tg along with a low variation of tan δ is observed for graphene loaded samples. A significant improvement in both compressive and flexural strengths are reported for these specimens. Resistivity measurements demonstrates early degradation in epoxy onlysamples compared to graphene loaded ones. The extent of degradation is higher for specimens subjected to electric current compared to oven heated samples. The study is expected to broaden the understanding of using small amounts of graphene (1.4-2.8 wt.% of epoxy) as a filler to abate electric current induced damages in carbon fiber epoxy composites.