An infrared microscope system was used to measure the temperatures at the interfaces of graphite-epoxy and carbon-PEEK composites in unidirectional sliding contact with sapphire. Effects of fiber orientation and velocity on tribological parameters were examined. Oscillating contact conditions with graphite-epoxy were also examined. Surface temperatures on the order of 100-160°C were measured at relatively low rates of frictional heat generation. The corresponding coefficients of friction were on the order of 0.45-0.65. In graphite-epoxy, fiber orientation was seen to affect coefficient of friction and wear significantly; but surface temperature was very little affected by fiber orientation. In carbon-PEEK, fiber orientation affected the coefficient of friction, wear and surface temperatures significantly. Surface temperatures in both materials initially increased with velocity, but stayed constant as the glass transition temperature of the matrix material was reached. The total wear is believed to be due to a combination of adhesive wear and fatigue wear. Comparison of the measured surface temperatures with theoretical predictions is done. A “two-velocity-regime” tribological model is proposed to explain the tribological behavior of polymer composites. / Master of Science