Date of Award
Doctor of Philosophy
Regenerative braking in conjunction with friction braking represents one of the most common braking strategies employed in electric and hybrid vehicles. As the friction brake accounts for about 5 to 85% of total braking in these “blended scenarios”, this warrants for more research into the development of new lightweight, wear resistant, and sustainable friction materials and also for reviewing the existing testing procedures.This research primarily focuses on generation of new knowledge related to development of environmentally friendly, lightweight friction material for vehicles with regenerative braking systems. A sample formulation was initially developed from knowledge gained by literature review and analysis of existing commercially available brake linings. Design of experiments based on Taguchi method and other statistical analysis tools were used to optimize the sample formulation. The density, porosity, shore D hardness, thermal stability, damping capacity of these pads were measured and compared with commercially available friction material. Pads were tested against commercially available rotors (ASTM A48 C30 gray cast iron) coated with ceramic material. Friction performance tests were completed using Universal Mechanical Tester (Tribolab by Bruker) and the scaled-down ISO SAE J2522 procedure. Friction surfaces of pads and rotors were analyzed in order to understand their surface chemistry and morphology, as well as their impact on performance of the tested friction material. The final optimized pad based on design of experiments (DOE 9) showed high and stable friction levels in high temperature sections (Section 9, Section 12.2 and Section 14 in ISO/SAE J2522 testing procedure) and excellent recovery capabilities at lower temperatures (Section 10, Section 13 and Section 15). This pad material was compatible with coated rotors, had low wear, and meets all the industry specifications and standards. SEM and EDX analysis showed that the pads developed stable friction layer on the friction surfaces and this capacity to develop friction material contributed towards overall friction stability of the material.
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