Assessing wire EDM as a novel approach for CFRP drilling: performance and thermal analysis across lay-up configurations

Abstract

Conventional drilling of carbon fibre–reinforced plastic (CFRP) presents significant challenges due to the material’s abrasive nature and anisotropic properties, leading to tool wear, delamination, and surface damage. To address these challenges, this study pioneers the use of wire electrical discharge machining (WEDM) to evaluate the drilling performance of thick CFRP lay-up configurations mainly unidirectional and multidirectional, marking the first application of WEDM for CFRP drilling. The study evaluates material removal rate (MRR), delamination factor (DF), and surface damage while employing an analytical solution to estimate surface temperature and heat conduction in the laminates. An eight-full factorial experimental design was employed, involving variations in ignition current (3 A and 5 A) and pulse-off time (4 µs and 8 µs). The findings revealed that the multidirectional lay-up achieved an MRR of 2.85 mm3/min, significantly outperforming the unidirectional lay-up’s MRR of 0.95 mm3/min, representing a 300% increase at 5 A and 4 µs. However, the increase in discharge energy led to surface damage such as delamination, frayed fibres, and irregular circularity, especially evident in the unidirectional lay-up. For delamination, the multidirectional lay-up had the highest top DF of 1.4 at 5 A and 6 µs, while the unidirectional lay-up achieved the peak bottom DF of 1.24 at the same levels. While none of the parameters significantly affected the responses, the current exhibited the highest contribution ratios. Analytical predictions of the thermal distribution indicated a 45-µm delamination length at the laminate surface and depth, aligning closely with experimental predictions of 30–50 µm.