Pitch-based high modulus carbon fibers were oxidized in air and characteriz
ed using the coulostatic method in order to compare them with anodized fibe
rs. The interfacial shear strength (IFSS) of these fibers to an epoxy resin
was evaluated by a micro debonding test. The results showed a good correla
tion between the differential double layer capacities, Cd, which were measu
red by the coulostatic method, and the IFSS values for air-oxidized and ano
dized fibers. In order to investigate the variation of the air-oxidation an
d anodization in the tow, the coefficients of variation for the Cd and pola
rization resistance (Rp) by the mono-filament coulostatic method were compa
red. As a result, the variation of oxidation in the tow of air-oxidized fib
er seemed to be slightly larger than that of anodized fiber. (C) 1999 Elsev
ier Science Ltd. All rights reserved.