The micrographs of epoxy resin on single carbon fiber at room temperature and the temperature dependent contact angle on single carbon fiber were investigated using field environmental scanning electron microscope (FESEM).The results showed that the contact angle decreases significantly with increasing temperature.The advantage of this experimental approach was that can directly reflected the wettability of epoxy resin to fiber.But the experimental process was complicated

and there were many influence factors.The reason is that the wettability of epoxy resin on parallel sheet can be improved at higher temperatures.The spreading procedures for the epoxy resin droplet on carbon fiber cluster were observed by means of drop shape analysis system (DSA) in parallel and perpendicular directions of the aligned fibers.It was found that the temperature dependent contact angles were quite distinct from the different observed directions.Moreover

the contact angles observed perpendicular to the direction of fibers are consistent with the results on the single carbon fiber

which indicates that the wetting behavior of epoxy resin to the fiber in the direction parallel to the fiber cluster can truly represent the wettability.Then

the complicated method about single fiber of using FESEM to understand the wettability of epoxy resin to fiber could be replaced by using DSA.It should save much time and energy for the practical industry.