Experimental investigation on the drilling of carbon fiber-reinforced polymer composite using micro-electrochemical discharge machining process

Carbon fiber-reinforced polymer (CFRP) composites are widely used in aerospace, electronics, and high-performance engineering applications due to their excellent material properties. Drilling holes in CFRP presents significant challenges for conventional methods due to the material's anisotropic and heterogeneous nature, which can lead to issues such as delamination, fiber pull-out, and reduced dimensional accuracy. To overcome this challenge, advanced hybrid techniques like micro-electrochemical discharge machining (µ-ECDM) are widely used for machining these materials. This study examines the impact of key µ-ECDM parameters, including voltage, duty factor, electrolyte concentration, and frequency, on the quality of holes. The delamination factor and radial overcut (ROC) are analyzed as key response variables to evaluate machining performance. The experiments were conducted using the Box-Behnken design, with process optimization performed using response surface methodology. The optimal results indicate that the minimum observed values for DE and ROC, measured as 1.23 and 177.24 µm, respectively, were achieved under machining conditions of 40 V voltage, 60% duty factor, 15 wt.% of NaOH for the concentration, and 10 kHz pulse frequency. Field-emission scanning electron microscopy analysis revealed fiber breakage, along with the re-deposition and adhesion of fractured fibers and the matrix material around the edges of the micro-hole.