A gradient anodic oxidation method for treating polyacrylonitrile‐based high‐modulus carbon fibers

We describe a gradient anodic oxidation method. Polyacrylonitrile-based high-modulus carbon fibers were treated by the conventional and gradient anodic oxidation methods. The results show that the carbon fibers treated by the gradient method possessed a more stable tensile strength, larger NaOH uptake, shallower striations, flatter fracture surface of composites, and better interlaminar shear strength compared to those treated by the conventional method. This indicated that the gradient method was more effective in restricting the etching reaction and improving the adhesion between the carbon fibers and matrix, and we give a suggested explanation of the mechanisms. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1059-1066, 2011