Effect of high graphite filler contents on the mechanical and tribological failure behavior of epoxy matrix composites

This work evaluates the effect of the presence of high graphite contents on the mechanical and tribological properties of epoxy matrix and carbon fiber reinforced epoxy matrix composites. Epoxy matrix composites containing 0-30 wt%-graphite were prepared by hand mixing. Graphite/epoxy fiber composites containing 0-11.5 wt%-graphite were also prepared. The produced materials were characterized regarding mechanical properties, including experimental and numerical analysis, and sliding wear resistance. Experimental results show that the addition of high graphite amounts results in materials with increasingly high elastic modulus. However it also results in increased brittle behavior, significantly reducing failure strain for additions above 12.5 wt%. Shear modulus and flexural shear modulus also increase with graphite addition. The presence of graphite in the epoxy matrix decreases subsurface fatigue wear and increases wear resistance, as a result of graphite lubricant action. Graphite/epoxy composites reinforced with carbon fiber present higher mechanical performance than conventional carbon fiber reinforced epoxy matrix composites. Attained results show that a maximum graphite concentration must be found to allow equilibrium between increased stiffness and wear resistance, and reduced fracture behavior. Nevertheless increasing graphite concentration above values commonly used in the literature appears to open an opportunity window for the processing of low cost hybrid materials combining high specific strength, increased conductivity and self-lubricant properties.