Tuning the interface in epoxy-based composites and laminates through epoxy grafted graphene oxide enhances mechanical properties

Improved dispersion together with enhanced interfacial adhesion of the reinforcement is the key to superior structural properties in polymer nanocomposites. Herein, graphene oxide (GO) is employed to reinforce epoxy, and in order to improve the interfacial adhesion, epoxy chains were grafted directly onto GO prior to composite preparation. The functionalized GO sheets were systematically characterized using FTIR, TEM, Raman spectroscopy, XRD, and XPS. The epoxy composites with GO and epoxy grafted graphene oxide (Ep-g-GO) were prepared with the addition of only a small amount (0.5 wt%) of GO using a mechanical stirrer coupled to a bath sonicator. This strategy resulted in an impressive increase in mechanical properties, 40% in storage modulus, 70% in hardness, 39% in fracture toughness, and 8% in tensile strength, as compared to neat epoxy. In addition, the modified composites were thermally stable up to 300 °C as inferred from the thermogravimetric analysis. The enhanced properties of the composites further led to investigating the effect of Ep-g-GO on epoxy/carbon fiber (CF) laminates. Interestingly, incorporation of 0.5 wt% Ep-g-GO resulted in improved interfacial adhesion between GO and the epoxy matrix, which enhanced the tensile strength by 12% and inter-laminar shear strength by 9% as compared to neat epoxy/CF laminates. This study clearly demonstrates the positive effect of the tailored interface, offered by Ep-g-GO, on the mechanical properties of epoxy composites and epoxy/CF laminates.