ABSTRACTThe present work investigates the effect of applying direct current electric voltage to the sliding surfaces on the friction coefficient displayed by epoxy composites sliding against dry and water wetted steel surface. Iron and copper particles and wires were used to fill and reinforce epoxy matrix. It was found that, when no voltage was applying on the contact surfaces friction coefficient of the epoxy composites displayed the highest values. As the voltage was applied to the contact surfaces friction coefficient significantly decreased. Significant friction decrease was observed for epoxy composites filled by graphite. PTFE addition into epoxy composites displayed further friction decrease. As the voltage increased friction coefficient decreased, where the same trend was observed regardless the voltage charge. In the presence of water on the sliding surfaces the effect of graphite diminished, where water exchanged the electric static charge between the two sliding surfaces. As the voltage increased friction coefficient drastically decreased. Based on the low value of friction it is recommended to use this sliding condition in application. Composites reinforced by iron wires displayed drastic decrease in friction coefficient, while slight friction increase was accompanied to the performance of composites filled by iron particles. Reinforcing epoxy by copper wires displayed relatively lower friction values than that observed for composites reinforced by iron wires. In the presence of water on the sliding surfaces, significant friction increase was observed for composites reinforced by iron wires and iron particles. As the voltage increased friction coefficient significantly increased. Based on these observations it can be recommended to avoid the application of those composites when water is the lubricating medium. Friction coefficient of the tested composites reinforced by copper wires showed lower values than that observed for iron wires.
A. M. Samy (Mon,) studied this question.