Effects of Adding Graphite to Epoxy Resin on its Mechanical Properties and Mild-to-Severe Wear Performance at its Heat Distortion Temperature

In this study, epoxy/graphite composites were fabricated based on different weight fractions (0, 3, 6, and 9 wt.%) of graphite powder for bearing applications. The mechanical and tribological properties were assessed. Adhesive wear tests covered the severe regions, where the interface temperature (IFT) exceeded the heat distortion temperature (HDT) of the epoxy. Graphite additions improved elastic modulus and hardness but decreased fracture strain and toughness of the composites. The tribological behaviors in the mild wear region were improved as the graphite content increased. In the mild wear region, the increase in graphite additions showed a good improvement by reducing the specific wear rate (SWR) and coefficient of friction (COF). In the severe wear region, the neat epoxy and higher graphite concentrations exhibited a dramatic increase in SWR, whereas the lowest addition of 3 wt.% exhibited good wear performance. For epoxy, the reason was that IFT exceeded its HDT, while the aggregation of graphite particles was the main reason in the case of higher graphite concentrations. SEM examinations showed severe wear signs—high ploughing and fracture—when IFT exceeded the HDT. However, by reducing the IFT, graphite additions did not show such severe wear features due to the accelerated heat dissipation.