AbstractsPhysics

As a very important component of automatic transmissions, torque converters are one of the most complicated parts in vehicles. Wet friction materials which are present in torque converter clutches attract attention because improvements made on these composite materials lead to better fuel efficiency and driving comfort. It is important to understand the possible interactions between wet friction materials and automatictransmission fluid (ATF) as the efficiency of the system highly depends on them.In the first part of this study, we report a novel method to measure the adsorption energy between a liquid adsorbate, ATF, and a solid adsorbent, wet friction material, using differential scanning calorimetry. Studies involving different adsorbents i.e. a wet friction material and its individual ingredients and different adsorbates i.e. a commercial ATF, base oil, and custom made oils were used for the development of the method. Besides, the measurements were useful for understanding possible types of intermolecular interactions occurring during adsorption.Secondly, excimer laser treatment was performed on the wet friction material together with its fiber components. It was shown that the adsorption energies of each adsorbent increased as a result of the treatment. Adsorption energy measurements were also performed on some minerals/clays which could be used as fillers in wet friction materials. Friction performances of some of these fillers, which were tested using an SAE#2 tester, showed a correlation with their adsorption energies. In order to provide better understanding for the performance of wet friction materials, different friction modifiers were used to study the friction performance and surface energies after adsorption. In case of both the friction modifier concentration and structure, the friction performances of the materials were found to correlate with their contact angles, contact angle hysteresis, and surface energies.In the last part of the study, polymer resin-based, paper-type wet friction materials were made using different fiber/filler ratios with the most commonly used ingredients in the industry. The effect of these ratios on the mechanical properties and porosities of the materials were characterized using different techniques. Once the tribological performances of these materials were evaluated, it was noted that the material consisting of 50/50 fiber/filler had the optimum composition considering the mechanical and tribological performance of the materials. Advisors/Committee Members: Sancaktar, Erol (Advisor).