Investigation on scratching force and material removal mechanism of 3D SiCf/C–SiC composites during single grain scratching

Abstract

As one of the novel fiber-reinforced ceramic matrix composites, SiCf/C-SiC composites are difficult to machine materials and the material removal mechanism is not completely clear yet. Single grain scratching tests with gradual depth have been carried out to analyze the influence of fiber orientation and woven structure on the material removal mechanism and scratching force in three typical scratched surfaces defined by the fiber orientation. Results indicate that the scratching force waveform is affected by the weaving method, fibers orientation, and porosity distribution of the scratched area, resulting in periodic fluctuations. Diamond indenter causes greater damage to the surface of SiCf/C-SiC composites when scratching along transverse fibers, while leaving narrow but deep grooves on the surface when scratching along perpendicular fibers. The dominant mode of material removal of SiCf/C-SiC composites is brittle fracture, and the damage features mainly include direct fiber breakage, matrix fragmentation, fiber pullout, fiber outcropping.