A Tribological Investigation of Carbon Carbon Composites and the Affect of Roughness and Waviness Parameters on Friction Performance

Friction performance parameters of two types of carbon-carbon (CC) composites were tested using a sub-scale dynamometer for 100 stops. Worn surface profiles of each sample were measured using a Taylor Hobson Surtronic 3+ profilometer. Roughness and waviness parameters collected from the profilometry testing were compared to weight loss, thickness loss, effectiveness, stop time, and torque of each carbon-carbon composite type. The comparison shows for an increase in torque and effectiveness, and a decrease in stop time, with a 90% confidence there is a 29% decrease in skewness (Rsk), 150% decrease in high spot count (RHSC), an 18% increase in maximum valley depth (Rv), a 38% increase in mean spacing of local peaks (RS), and a 20% increase in mean arithmetic wavelength (Rla) with an increase in torque when roughness is analyzed. For waviness profiles, the comparison shows for an increase in torque and effectiveness, and a decrease in stop time, with a 90% confidence there is a 55% decrease in skewness (Rsk), 29% increase in high spot count (RHSC), a 31% increase in maximum valley depth (Rv), a 26% increase in mean spacing of local peak (RS), and a 4% increase in mean arithmetic wavelength (Rla). Furthermore, there are differences in both friction performance and surface topography between the CC composite types which can be attributed to the differences in fiber orientation and microstructure at the wear faces.