Hole exit quality and machined surface integrity of 2D Cf/SiC composites drilled by PCD tools

The brittle matrix and the anisotropic reinforcing phase of Cf/SiC composites bring great challenges to the machining process. Polycrystalline diamond (PCD) tool was used to drill 2D Cf/SiC composites. The influence of thrust force on hole exit defects was analyzed, and the transformation rule of material removal mechanism and surface generation of hole were studied. With the increase of feed rate, the thrust force increased and the hole exit defects increased. Specific drilling energy was used as an index to quantitatively describe the energy consumption of material removal. With the increase of feed rate and the decrease of cutting speed, the brittle fracture mode of carbon fibers changed from micro-brittle fracture inside carbon fiber to macro-brittle fracture. Although the machined surface of carbon fibers produced by micro-brittle fracture was composed of many micro-fracture, the hole surface was flat overall. Therefore, the hole surface roughness was small.