Electromechanical Behavior of the Copper-Based Graphene- and Al2O3- Reinforced Hybrid Composite Electric Motor Brushes

This study investigates the fabrication and characterization of electric motor brushes, which serve as critical conductive and wear-resistant components in direct contact with the motor’s rotor. Copper-matrix composites reinforced with varying concentrations of graphene and alumina (Al2O3) were produced across two distinct experimental groups. Following an 8-hour mechanical alloying process, the composite powders were consolidated using a single-acting hydraulic press. The resulting compacts were then sintered at 900°C (1 hour) in a reducing environment. Electromechanical evaluations were conducted in triplicate at a constant spring pressure (100 kPa), varying rotational speeds (8–32 m/s), and current densities (4–16 A/cm2). The study further assessed the electrical conductivity, porosity, hardness, and mass loss of each specimen. Results indicate that electrical conductivity declined as the reinforcement ratio increased. Regarding tribological performance, the minimum friction force (0.08 N) was recorded for the 5 wt. % graphene and 1 wt. % Al2O3 composition. Meanwhile, the lowest voltage drop (0.03 V) was observed in the 10 wt. % Gr and 0.5 wt. % Al2O3 sample. Although hardness generally decreased with higher reinforcement content. On the other hand, the copper-based composite containing 10 wt. % Gr and 0.5 wt. % Al2O3 exhibited the maximum hardness value of 13.8 HB.