The Machining Characteristics of Drilling Multidirectional CFRP Using Wire Electrical Discharge Machining

Abstract This paper examines the feasibility of wire electrical discharge machining (WEDM) on drilling multidirectional carbon-fibre-reinforced plastic (CFRP) composite laminates using high-performance wire electrodes. A full factorial experimental array of 8 (23) tests was employed to evaluate the effect of varying the machining parameters including pulse-on time (0.6 and 0.9 µs), pulse-off time (4 and 6 µs), and wire type (Compeed and Topas Plus D) on the material removal rate (MRR), top and bottom delamination factor (DFT and DFB) and surface integrity. The results revealed that the MRR varied between 1.35 and 2.9 mm3/min and increased by high pulse on time and low pulse off time as a result of the higher discharge energy generated. Despite, none of the parameters having a significant effect on MRR, the pulse-off time was found to have the largest percentage contribution ratio (PCR), with a value of 71.8%. The Topas Plus D wire exhibited a higher MRR (up to 21%) under the same cutting conditions compared to the Compeed wire electrode. Regarding the delamination, the top and bottom factors ranged from 1.06 to 1.20 and 1.08 to 1.25 respectively. The pulse-on time and its interaction with the pulse-off time had the highest PCR on DFT, with values of 26.86% and 38.21%, respectively, according to ANOVA, which showed that none of the parameters had a significant impact on delamination. Optical micrographs of the workpiece revealed the presence of defects in terms of poor hole quality/roundness error, frayed fibres, excessive delamination, and adhered debris (including wire electrode contaminants) on both the top and bottom surfaces. These defects tended to be more noticeable in experiments using the Compeed wire electrode, probably as a result of the higher discharge energies.