Investigation of in-plane and out-of-plane micro-hole drilling on 2D-Cf/ SiC composites

Carbon fiber-reinforced silicon carbide matrix composites (Cf/SiCs) are extensively utilized in the field of aviation and aerospace because of their superior mechanical qualities. However, it is difficult to machine highquality small holes on them. To investigate the characteristics of micro-drilling on Cf/SiCs, the polycrystalline diamond (PCD) tool was used to machine holes on the in-plan and out-of-plan surfaces of Cf/SiC composites. The drilling force, the hole morphology and quality were explored. The mechanisms of material removal and tool wear were studied. The size effect during the micro-drilling process was also investigated. The outcomes showed that the out-of-plane drilling process yielded more thrust force and torque than the in-plane drilling process. The main forms of damage at the hole entrance and exit are tearing and burrs during in-plane drilling. The damage is mainly in the form of edge breaking caused by debonding and fracture of longitudinal fiber during out-of-plane drilling. The surface defects of the hole exit and entrance during out-of-plane drilling are fewer than those during in-plane drilling. The roundness errors of holes during in-plane drilling are fewer than those during out-of-plane drilling. Additionally, the surface roughness of the hole wall during in-plane drilling is less. Besides, brittle and ductile removal areas were observed at different fiber orientation angles (FOA). Furthermore, the rapid rise in specific cutting energy and the deterioration of surface quality when the feed rate is much smaller than the cutting edge proves the presence of the size effect. A new observation was that the abrasive wear of the flank face and chisel edge during out-of-plane drilling was more severe than that of in-plane drilling.