Interfacial microstructure and mechanical properties of carbon fiber composite modified with carbon dots

The weak interfacial adhesion between carbon fiber (CF) and resin matrix is an urgent problem that researchers have been attempting to ameliorate. Sizing can effectively improve the interfacial adhesion between CF and resin matrix, which is extensively used in CF industrial preparation process. In this study, a novel simple two-step sizing method was adopted to improve the interfacial properties of the CF/epoxy (CF/EP) composite. The CF was initially covered by carbon dots (CD). Subsequently, the sizing agent (SD) was more evenly sized on the CF surface by the bridge of CD. The sized CF was characterised by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The interface of the CF composite was characterised by SEM and atomic force microscopy (AFM). The results show that CF-CD-SD/EP exhibited good interfacial adhesion due to the synergistic effect of CD and SD. The interlaminar shear strength (ILSS) value of the resulting composite increased by 16.21% and 38.49% when compared with those of CF-SD/EP and desized CF/EP, respectively. This method has potential applications in the CF industry.