Machinability of carbon/epoxy composites by electrical discharge machining

Abstract

Through-thickness drilling of carbon/epoxy laminate by electrical discharge machining (EDM) was conducted using copper and graphite electrodes. Gap current and pulse-on time were varied and their effect on machinability of the composite laminate was assessed in terms of material removal rate, electrode wear, delamination factor, hole taper and deviation in hole size. It was found that the highest material removal rates were obtained with graphite electrode at the highest current and highest pulse-on time. On the other hand, these conditions also corresponded to the highest electrode wear rate, highest delamination damage and largest deviation in hole size. Hole taper was the least at these settings. An optimum set of conditions for EDM drilling could not be found within the ranges of parameters tested. However, due to the interaction between process parameters it is found that at intermediate levels of pulse-on time levels of delamination damage and deviation in hole size are the smallest. Therefore, effective EDM drilling with high MRR and low damage may be performed at high currents and intermediate pulse-on time.