Investigation on machined surface quality in ultrasonic-assisted grinding of C_f/SiC composites based on fracture mechanism of carbon fibers

As a kind of carbon fiber-rich material, the machined surface quality of C_f/SiC composites is greatly affected by the fracture mode of carbon fibers. Therefore, exploring the material removal mechanism of C_f/SiC composites in grinding through the different fracture mechanisms of carbon fibers from the perspective of microstructure is necessary. In research, the micro-scale fracture mechanism of carbon fibers and the transformation of mechanism were explored. The difference in fracture behavior of carbon fibers caused different energy consumption in material removal, which is instructive for monitoring the machining process with specific grinding energy. The difference of machined surface morphology was directly caused by the difference of material removal mechanism, which can be effectively characterized by the machined surface roughness. The transition of the material removal mechanism was determined by the maximum undeformed chip thicknesses. Ultrasonic-assisted grinding promoted the removal of carbon fibers in nano-scale brittle fractures by reducing the maximum undeformed chip thicknesses, thereby improving the quality of the machined surface.