Ultrasonic-Assisted Grinding (UAG) is a novel manufacturing technology that shows promising promise for use in processing Ceramic Matrix Composites (CMCs). Nevertheless, analyzing the material removal process of CMCs with multidirectional structure during UAG is challenging, impeding the progress and improvement of the UAG process. This work examined the impact of ultrasonic vibration on the dynamic mechanical characteristics during processing. Additionally, we experimentally elucidated the material removal mechanism of CMCs during the scratching process under the influence of vertical vibration. The results indicate that the introduction of ultrasonic vibration causes a strain rate effect, resulting in a modification of the material removal mechanism, subsequently impacting the processing quality. Ultrasonic vibration increases the dynamic strength and brittleness of the fibers in CMCs, leading to more cracks at fracture, which changes from the original bending fracture to shear fracture. In addition, ultrasonic vibration can effectively inhibit the impact of scratching depth and anisotropy on the removal mechanism of CMCs, resulting in a more uniform surface of CMCs after processing.

SiC_f/SiC ceramic matrix composites (SiC_f/SiC composites) are difficult to drill small holes due to their heterogeneity, high hardness, and low electrical conductivity. In order to solve the difficulties of poor quality and low efficiency when drilling small holes, a novel femtosecond laser rotary drilling (FLRD) technique is proposed. Beam kinematic paths and experimental studies were carried out to analyze the effects of processing parameters on the drilling results in the two-step drilling process. In the through-hole drilling stage, the material removal rate increases with increasing laser power, decreasing feed speed and decreasing pitch. As for the finishing stage of drilling, the exit diameter increased with increasing laser power and decreasing feed speed. The drilling parameters were selected by taking the processing efficiency of through-hole and the quality of finished hole as the constraint criteria. Holes with a diameter of 500 μm were drilled using FLRD in 3 mm thick SiC_f/SiC composites with a drilling time < 150 s. The hole aspect ratio was 6, the taper < 0.2°, and there was no significant thermal damage at the orifice or the wall of the hole. The FLRD provides a solution for precision machining of small holes in difficult-to-machine materials by offering the advantages of high processing quality and short drilling times.