Investigation of milling performance and removal process mechanism of 3D SiCf/C-SiC composites using brazed diamond tools

Abstract

The present paper evaluates the machinability of brazed diamond tools for milling 3D SiCf/C-SiC composites. Defined three milling modes of fiber orientation, transverse, longitudinal, and perpendicular, and surfaces, SA (transverse and longitudinal), SB (transverse and perpendicular), and SC (longitudinal and perpendicular), are chosen to reveal factors influencing milling force and surface integrity. Besides, the removal process mechanism is analyzed through high-speed cameras. The results show that combining fiber orientations influences milling force waveform, whereas surface quality is related to fiber orientation and damage types. The lower cutting speeds obtain better surface quality on SA surfaces, while superior surface quality on SB and SC surfaces is attained with higher cutting speeds. Dominant damage modes include direct fiber breakage and matrix fragmentation. Moreover, the removal process is sequentially matrix cracking and fiber/matrix debonding, fiber breakage, and ultimate failure. Toughening mechanisms of composites containing fiber bridging and fiber pullout are observed during milling.