ADHESION TO CARBON-FIBER SURFACES - SURFACE CHEMICAL AND ENERGETIC EFFECTS

IM6 carbon fibers have been surface treated in steps to 20, 200 and 600% as well as the nominal 100% surface treatment. Quantifiable changes in the surface oxygen and nitrogen composition as well as in the surface energetics have been measured and compared against the untreated IM6 fiber. Single fiber fragmentation testing of these fibers in an epoxy matrix has shown that there is a direct effect of the surface chemical changes on fiber-matrix adhesion. Composites were fabricated from these same materials, and interlaminar shear, transverse flexural and Mode II fracture toughnesses were measured. Results showed that the composite shear and transverse flexural strengths were significantly increased after only the 20% surface treatment level, with further increases in the surface treatment lever having only a minor effect. However, Mode II fracture toughness continued to increase with increasing surface treatment.