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

IM6 carbon fibers have been surface treated in steps to 20, 200 and 60 0% as well as the nominal 100% surface treatment. Quantifiable changes in the surface oxygen and nitrogen composition as well as in the surf ace energetics have been measured and compared against the untreated I M6 fiber. Single fiber fragmentation testing of these fibers in an epo xy matrix has shown that there is a direct effect of the surface chemi cal 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 co mposite shear and transverse flexural strengths were significantly inc reased after only the 20% surface treatment level, with further increa ses in the surface treatment lever having only a minor effect. However , Mode II fracture toughness continued to increase with increasing sur face treatment.