Assessment of machined surface for SiC_f/SiC ceramic matrix composite during ultrasonic vibration-assisted milling-grinding

As a new advanced material, silicon carbon fiber-reinforced silicon carbon ceramic matrix composite has attracted increasing attention and would have a promising application in prospect owing to its superior properties such as low density, high strength, and high-temperature resistance. However, there is still no such standard criterion for machined surface quality evaluation of fiber-reinforced ceramic matrix composites or fiber-reinforced composites. Thus, in this paper, investigations have been performed on ultrasonic vibration-assisted milling-grinding SiC fiber-reinforced SiC-based ceramic matrix composite. It aims to propose a primary criterion for the machined surface assessment of fiber-reinforced composites. This study considered and tested fiber-reinforced composites such as SiC_f/SiC CMC, C_f/SiC CMC, and CFRP. Due to the large size of pits and voids in the machined surface, it was recommended to use non-contact measuring equipment for surface quality measurement. The 2D surface roughness value of every single machined surface differed much along different measuring directions and regions. Then, the 3D surface roughness was suggested for describing the machined surface quality as its data fluctuation was much more minor than the 2D roughness. The comparative analysis found that the measuring area size significantly influenced the 3D roughness result. This study used a measuring area of 13 × 13 mm², 11 × 11 mm², 7 × 7 mm² for SiC_f/SiC CMC, C_f/SiC CMC, and CFRP, respectively, taking into consideration the measuring time consumption and the reliability of measured data.