Influence of Drilling Parameters on Tool Wear, Delamination, and Surface Integrity of 3D Carbon–Carbon Composites

Abstract

Carbon fibre-reinforced carbon matrix (C/C) composites are advanced engineering materials widely employed in aerospace and thermal protection systems due to their excellent strength retention and thermal stability at extremely high temperatures in non-oxidizing environments. However, their anisotropic and heterogeneous structure makes them difficult to machine, often resulting in defects such as delamination, fibre pull-out, surface damage, and rapid tool wear during drilling operations. In the present study, the drilling performance of 3D carbon–carbon composites was experimentally investigated using carbide-based drill tools under dry machining conditions. Drilling experiments were conducted at spindle speeds of 300, 700, and 1000 rpm and feed rates of 20, 40, and 60 mm/min. The effects of machining parameters on tool wear, drilling temperature, hole roundness, delamination factor, and surface roughness were evaluated using optical microscopy, coordinate measuring machine (CMM) measurements, and surface characterization techniques. The results revealed that tool wear was primarily characterized by edge chipping, abrasion, and carbon particle adhesion. The drilling temperature remained relatively stable, ranging from 36.06 °C to 36.96 °C, owing to the high thermal conductivity of the composite. The minimum delamination factor of 1.0063 was obtained at 700 rpm, whereas the best surface finish (1.121 μm) and dimensional accuracy were achieved at 1000 rpm. The study demonstrates that appropriate selection of drilling parameters significantly improves hole quality and machinability of 3D carbon–carbon composites. The findings provide useful guidelines for optimizing drilling operations in aerospace and other high-temperature engineering applications.