Phenolic-based composites for automotive frictional materials contain a variety of inorganic fillers and modifiers in addition to combination of the base resin and fibers (mostly asbestos). The frictional behavior under low speed conditions cannot provide sufficient foundation for the prediction of friction and wear behavior at high speed because the temperature rise courses chemical changes in some frictional constituents of the composite system.
In the previous papers the high speed friction behavior of carbon and glass fiber composites has been studied. The purpose of this paper is to enable a clear interpretation of high speed friction performance of Aramid fiber composites comparing with two other systems. The following results have obtained:
(1) Frictional coefficient was reduced by incoeporation of the aramid fibers under low speed and high speed conditions. However, frictional coefficient increased under medium speed conditions when the fiber content was high.
(2) Frictional flucturations during sliding was significantly reduced with increasing amount of fibers for all sliding condition.
(3) The rate of wear was reduced with increasing amount of fibers and increasing with sliding speed. The aramid-fiber system was more resistant to wear than carbon fiber and glass fiber systems.

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A carbon fiber reinforced Nylon 66 was molded by a typical injection molding machine. The average fiber length and the breadth distribution of the length were examined in detail as a function of the fiber content or the injection conditions.
The fiber length became shorter with an increase of the fiber content. It is considered that the breaking of the fibers is mainly caused by the interference of the fibers, and the increase of viscosity. An increase in the injection speed led to considerably shorter fiber lengths. This is considered to be due to an increase in the shearing force with increasing flow speed of the resin. In these cases, the breadth of distribution of the length decreased slightly with decreasing length. On the contrary, the extent of decrease in fiber length became small with an increase of screw speed, and the breadth of the distribution remained nearly constant.

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