Influence of fibre surface oxidation–reduction followed by silsesquioxane coating treatment on interfacial mechanical properties of carbon fibre/polyarylacetylene composites

Carbon fibre was treated with oxidation–reduction followed by silsesquioxane coating method to improve the interfacial properties of carbon fibre/polyarylacetylene (CF/PAA) composites. The treatment method was divided into three phases, i.e., oxidation with oxygen plasma, reduction with LiAlH4, and coating treatment with vinyl silsesquioxane (VMS–SSO). The fibre surface composition and functional group were analyzed using X-ray photoelectron spectroscopy (XPS). The polar functional groups, especially C–OH which could react with Si–OH on silsesquioxanes, were increased after redox reaction. VMS–SSO coating treatment imported vinyl groups which could react with PAA resin during PAA cure process. The surface morphology of carbon fibre was observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The mechanical interfacial properties of the CF/PAA composites were characterized by short-beam bending testing method. Interlaminar shear strength (ILSS) of the CF/PAA composites in different treatment phases were increased by 31.7%, 28.8%, and 59.3%, respectively. The conclusion that oxidation–reduction followed by silsesquioxane coating treatment is an effective method to improve the interfacial properties of the CF/PAA composites can be drawn. This method can be used in other resin systems if the functional groups on silsesquioxane are changed according to those in resins.