Electric discharge drilling of micro holes in CFRP laminates

Carbon fiber reinforced plastics (CFRPs) are being used in various applications due to their light weight and good mechanical properties. However, conventional hole making in CFRPs results in defects like delamination and fiber pullout. Literature confirms the feasibility of producing defect-free holes using electric discharge drilling (EDD). The researchers have studied macro EDD in CFRPs but drilling of micro holes in CFRPs using electric discharge drilling has not completely investigated. The present research endeavor is an attempt to experimentally investigate the micro EDD process for CFRPs. A tungsten carbide electrode of diameter 120 mu m was used as a tool electrode. Several experiments were conducted using different tool geometries (i.e. solid, single notch and double notch) at different values of voltage, capacitance and tool speed. Single notch electrode was found to be the best electrode in getting high material removal rate (MRR), moderate tool wear rate (TWR) and high aspect ratio (29.17). At lower values of discharge energy, a better surface quality was observed during morphological analysis. A comparison was performed between the aspect ratio achieved in the present study and that available in the literature, the tabulated results highlight the achievements of the present experimental endeavor.