In this paper, either graphite (Gr) or carbon nanotubes (CNTs), or both of them were incorporated into carbon fabric reinforced phenolic (CFRP) composites, preparing by a dip-coating and heat molding process, the tribological properties of the resulting composites were investigated using a block-on-ring arrangement. The worn surfaces were observed by scanning electron microscope to understand the mechanism. Experimental results showed that the optimal Gr was more beneficial than CNTs in improving the tribological properties of the CFRP composites when they were singly incorporated. It is well worth noting that the friction and wear behavior of the CNTs-filled CFRP composites were improved further when Gr was added, indicating that there is a synergistic effect between them. Tribological tests under different sliding conditions revealed that the Gr and CNTs-filled CFRP composites seemed to be the most suitable for tribological applications under higher sliding speed and load, and oil lubrication.

The short carbon fiber reinforced polyimide (PI) composites filled with particulates of graphite were prepared by a heat molding technique. The friction and wear behaviors of PI composites sliding against GCr15 steel rings were evaluated on an M-2000 model ring-on-block test rig. It was found that the filler of graphite can significantly improve the wear resistance and decrease the friction coefficient of the PI composites. It was also found that the tribological properties of the short carbon fiber reinforced PI composites filled with graphite are closely related with the sliding condition such as sliding rate and the applied load.