PERFORMANCE OF AUTOMOTIVE FRICTION MATERIALS AT HIGH HUMIDITY

Interaction of friction brakes with external environment can considerably influence their performance which could relate to friction instabilities and friction induced vibration and noise. Humidity can alter the chemistry of friction surfaces that could relate to unwanted phenomena which may increase the cost of product. In addition to the chemical phenomena leading to unwanted reactions, there are physical effects related to adsorption of humidity and to modification of adhesion, accompanied with changes in contact surfaces and contact mechanics. Rotors and brake pads form the braking system of an automotive. The braking efficiency can be well assessed by studying the interaction of rotors and brakes. This thesis discusses bench top friction testing data, microstructure, and friction surfaces of two rotors namely cast iron and steel tested with two different brake materials namely non-asbestos organic and low metallic pads at high humidity (80% RH). Along with friction performance noise, vibration, and harshness (NVH) analysis is correlated to microstructure of these two rotors. The tests that are done are performed on Bruker’s Universal Mechanical Tester using scaling laws. Scaling factor is calculated based on comparison of real and small-scale specimen apparent contact area. Vibrational response and sound pressure levels are collected and characterized by using National Instruments USB DAQ and Lab-view modules. The microstructure analysis and surface topography analysis of two different brake pads were done by using Scanning Electron Microscope linked with Energy Dispersive Micro analysis. The performance differences of all combinations result from formation of different friction layer chemistry