Carbon fibers were modified by graft polymerization with acrylic acid (AA) using KMnO4/H2SO4 redox-induced system. The carbon fibers were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. After grafting, the absorbability of treated fibers might be enhanced and more pieces of tiny fragments stuck to the fiber surface. It was confirmed that grafting AA led to a remarkable increase in oxygen-containing functional groups of fiber surface. An about twofold increase in retained surface carboxylic acid groups occurred. The adhesion between carbon fiber and epoxy matrix was inspected by interlaminar shear strength and SEM. It was noted that the functionalized grafting coating of fiber surface gave rise to a strong interfacial bond, with little debonding. (c) 2008 Wiley Periodicals, Inc.