This article focuses on experimental studies on the wetting behavior between different carbon fibers (CFs) and epoxy as function of temperature, hardener addition, and progressive curing of the resin. The results indicate that surface sizing plays a key role in wettability of the CF with epoxy. There is a critical temperature for good-wetting of DGEBA-DDS mixture/CF. Complete wetting can be obtained for resin/CF after a period of curing time. Moreover, chemical reactions can not only improve the wettability but also strengthen interactions between the curing resin and CF. These results could provide an essential implication for understanding the formation process of interphase region of CF/epoxy composites. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013