Browse Publications Technical Papers 2024-01-3056
2024-09-08

Moisture Adsorption and Compression Deformation Behavior of Semimet vs. NAO Brake Pads: Effect of Pad Cure Temperatures and Moisture Adsorption on Low-Speed Friction 2024-01-3056

Moisture adsorption and compression deformation behaviors of Semimet and Non-Asbestos Organic brake pads were studied and compared for the pads cured at 120, 180 and 240 0C. The 2 types of pads were very similar in moisture adsorption behavior despite significant differences in composition. After being subjected to humidity and repeated compression to 160 bars, they all deform via the poroviscoelastoplastic mechanism, become harder to compress, and do not fully recover the original thickness after the pressure is released for 24 hours. In the case of the Semimet pads, the highest deformation occurs with the 240 0C-cure pads. In the case of the NAO pads, the highest deformation occurs with the 120 0C-cure pads. In addition, the effect of pad cure temperatures and moisture adsorption on low-speed friction was investigated: in both cases, the highest friction is associated with the pad cure temperature of 240 0C. As pad properties change all the time in storage and in service because of continuously changing humidity, brake temperature and pressure, one must question any approach trying to relate unused virgin pad properties to brake friction and noise in service, including any attempt to model or simulate brake friction and noise using virgin pad properties.

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