An experimental study on mechanical properties of epoxy-matrix composites containing graphite filler

The current work studies the effect of the incorporation of different amounts of graphite filler on the mechanical properties of epoxy resin and of carbon fiber reinforced epoxy composites. Graphite-reinforced epoxy-matrix composites were prepared with graphite fractions ranging from 5 to 30 wt%. The carbon-fiber reinforced graphite/epoxy hybrids were prepared using a fixed amount of carbon fiber, and graphite incorporation in the epoxy of 7.5, 10 and 11.5 wt%. After cure the produced materials were submitted to tensile and to flexural three point bending tests. Examination of microstructural features and fracture surfaces were undertaken by optical microscopy and scanning electron microscopy. Increased graphite filler contents results in improved tensile modulus of the epoxy matrix. The 7.5, 10 and 11.5 wt%-graphite materials showed also an increase in the ultimate stress value with increasing filler. Introduction of reinforcement carbon fibers enhances tensile modulus. This increase is higher for the higher amounts of graphite filler in the matrix. This study shows that graphite/epoxy composites reinforced with carbon fiber present higher mechanical performance than conventional carbon fiber reinforced epoxy matrix composites.