Effect of ozone-treated single-walled carbon nanotubes on interfacial properties and fracture toughness of carbon fiber-reinforced epoxy composites

In this study, superior mechanical properties were obtained for composite materials using single-walled carbon nanotubes (SWCNTs) subjected to a simple surface treatment. The effects of ozone-treatment on the surface properties of the SWCNTs/CFs/epoxy multi-scale composites were investigated in terms of interfacial properties and fracture toughness. The resultant surface free energy after ozone-treated SWCNTs (O-SWCNTs) markedly increased the polar component of the contact angle. In addition, the surface morphology image showed that the surface roughness of O-SWCNTs increased, suggesting that the surface roughness and the number of oxygen functional groups were effectively increased by ozone-treatment. Due to the surface modification, the interlaminar shear strength and fracture toughness of multilayered composites increased by 79.98% and 54.59%, respectively. This shows a direct linear relationship between the morphological changes of O-SWCNTs and the specific polar component of the surface free energy of the material as well as its mechanical properties.