Modification of carbon fiber by air plasma and its adhesion with BMI resin

Abstract

Carbon fiber (CF) was modified by air plasma at 30 Pa and 200 W with different treatment times. Interlaminar shear strength (ILSS) of CF/BMI composites suggested that air plasma-treated CFs showed better adhesion with BMI resins than the untreated resins; the maximum increment was 20.4% after plasma treatment for 900 s. Meanwhile, we investigated the surface changes of CFs using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The results indicated that air plasma treatment roughened the CF surfaces and improved the polarity of CFs by enhancing the polar group content. These changes were believed to be the major reasons for the improvement of interfacial adhesion. The fracture morphology observed by scanning electron microscopy (SEM) indicated that the fracture failure mode changed from adhesive failure to cohesive failure. After boiling in water for 48 h, the water absorption of the composites was low while the ILSS of the composites retained about 90%, which implied that the CF/BMI composites had good humidity resistance properties.