Effect of immediate curing at elevated temperatures on the tensile and interfacial properties of carbon fiber-epoxy composites

Elevated temperature conditions known to improve curing from the onset and during the process of immediate curing are not available in the field, which can hinder the mechanical performance of these strengthening systems. In this study, mechanical testing and material characterization were conducted to identify the effects of subjecting nanomodified epoxy and fiber-reinforced nanomodified epoxy composites to room temperature (RT) (30 °C) and elevated temperature (110 °C) from the onset of curing. Static tensile testing and interfacial adhesion tests were conducted to evaluate the mechanical performance. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were performed to determine curing characteristics to inform on the immediate curing of nanomodified resins cured under the two temperature conditions. Scanning electron microscopy was performed to identify Carbon nanotube (CNT) dispersion characteristics. Overall, due to the incorporation of CNTs in epoxy, RT curing results in upto 62% increase in strain at failure. By supplying additional energy during immediate curing with elevated temperatures, a 51% increase in strength and 42% increase in Youngs Modulus can be observed in the nanomodified epoxy. In CFRP-epoxy composites, due to the incorporation of CNTs in the epoxy, RT curing results in upto 27% increase in strain at failure. By supplying additional energy during immediate curing with elevated temperatures, upto 133% increase in strain at failure is observed and upto 17% increase in strength is observed. CNTs incorporated in CFRP-epoxy composites demonstrated upto 50% increase in interfacial adhesion whereas supplying additional energy for their immediate curing with elevated temperatures, upto 130% increase in interfacial adhesion was observed. TGA and DSC results supported the mechanical observations and show a need for immediate curing when CNTs are used in epoxy matrices.