Abstract
In order to study the influence of surface properties of carbon fiber on the adhesive strength between the fiber and resin matrix, measurement of 90 degree tensile strength (FT) has been carried out on unidirectional carbon fiber-epoxy composites (CFRPs). Twelve types or PAN-based carbon fiber were used, namely, carbonized or graphitized, surface treated or untreated, and from two different manufacturers. FT of CFRPs were 12 to 52 MPa and they increased with increasing in ILSS and in interfacial shear strength. Fr was 1/3-2/3 of ILSS and twice the in-terfacial shear strength for CFRP of each fiber. It increased with increasing in the amount of acidic surface groups, concentration of surface oxygen and active surface area. In the case of carbonized fiber, the correlation curve between Fr and the concentration of surface oxygen was only one, and the relationship between Fr and the amount of acidic surface group was represented into two curves belonged to each manufacturer. But, the relationship of FT and the active surface area gived two straight line for fiber of each manufacturer, including graphitized fiber.
