Carbon fibers have been subjected to surface treatment by amination in order to improve adhesion strength between the fibers and an epoxy resin at carbon fiber reinforced plastic (CFRP). XPS measurements confirmed the introduction of amino groups on the surface of carbon fibers by fuming nitric acid treatment followed by the reduction with sodium dithionate. The tensile strength of a single fiber was not affected by the amination of the surface. The interfacial shear strength (τ) of unmodified, nitrated and aminated carbon fibers was evaluated with the single fiber embedded test specimens. The introduction of amino groups was shown to improve the interfacial shear strength by about 30 % as compared with the unmodified fiber.
