Adsorption and Desorption Effects on Carbon Brake Material Friction and Wear Characteristics

The characteristics of the friction materials used in aircraft brakes are extremely important to the performance and safe operation of transport airplanes. These characteristics can change during exposure to environmental effects in the duty cycle, which can lead to problems, such as abnormally low friction, or brake induced vibration. Water vapor in the atmosphere produces a direct lubricant effect on carbon. Observed transition temperatures within the range of 140°C to 200°C, associated with increases in friction and wear of carbon brake materials, are attributed to water vapor desorption. Friction and wear transitions in the range of 500°C to 900°C may be associated with oxygen desorption.