C/C複合材料の曲げ強度に対する炭素繊維の表面構造の効果

抄録

The carbon fibers, the surface of which was hydrogenated and oxidized, were sub-mitted to be examined concerning the effect of the surface structure of carbon fiber on the strength of C/C composite. After the sizing agent on carbon fiber surface was first removed by boiling with ethyl methyl ketone, the surface was hydrogenated with H₂ at 1000°C and further the surface hydrogenated was oxidized with aqueous H₂O₂ solution at the boiling temperature for various hours respectively. The amount of surface oxides, in this case, was measured by means of alkali titration, on the assumption that the surface oxides belong to the acidic groups such as hydroxyls, carboxyls and so on. The tensile strength of carbon fibers barely changed through such chemical surface modifications. It was found that the bending strength of C/C composites, in which the carbon fibers had been used as a reinforcing filler, linearly increased with an increase in the amount of surface acidity, that is, the surface acidic sites played a major role in the increase of the bending strength of C/C composite.
Such effects of surface oxides could be ascribed to the strong adhesion between the fiber surface and the binder in the first stage and the following formation of C-C bond between the fiber surface and the binder the pyrolysis of surface oxides, during the molding of composite by means of hot-pressing.