Comprehensive Analysis of Lubricant and Nanofiller Contributions to Surface Roughness Control in Drilling of GFRP Composites

This study investigates the influence of hybrid additives and cutting parameters on the surface roughness (R_a) of drilled Glass Fiber Reinforced Polymer (GFRP) composites. Nine composite panels were fabricated with varying concentrations of wax (0%, 1%, 2%) and graphene (0%, 0.25%, 2%). Drilling experiments were conducted on a CNC milling machine using a range of cutting velocities (50–200 m/min) and feeds (0.02–0.08 mm/rev), and the resulting surface roughness was measured using a profilometer. The results demonstrate that cutting velocity is the most dominant parameter, contributing to 69% of the variability in surface roughness, followed by feed (16%). The incorporation of additives, specifically 1 wt% wax and 0.25 wt% graphene, produced a synergistic effect, yielding the lowest average surface roughness (≈2.9 µm) and the most stable machining process. Higher cutting velocities increased roughness due to thermal effects, while increasing feeds improved surface finish by reducing frictional heating. The findings indicate that an optimal combination of moderate additive concentrations and controlled machining parameters can significantly enhance the surface integrity and process repeatability in the drilling of GFRP composites.