Longitudinal ultrasonic vibration effects on grinding mechanism in side and end grinding of 2.5D Cf/SiC composites

As typical ablation-resistant materials, carbon fiber–reinforced ceramic matrix composites (CMCs) are widely used as hot-end components such as rocket launcher nozzles. Nevertheless, their characteristics of anisotropic and hard-brittle bring processing challenges. Rotary ultrasound–assisted machining (RUM) is an effective machining method for hard-brittle materials. In this paper, we established a single abrasive grit trajectory model and elucidated the trajectory characteristics of the grits under ultrasonic-assisted side grinding (UASG) and ultrasonic-assisted end grinding (UAEG). Then the effects of longitudinal ultrasonic vibration on the grinding force, and surface quality in UASG and UAEG of 2.5D Cf/SiC composites were investigated by the single-factor test. Finally, the grinding mechanism under the two processing methods was revealed. The experimental results showed that the longitudinal vibration in the two machining methods has different effects on the grinding force and surface roughness. After the application of longitudinal vibration, the reduction of grinding force in the side grinding process was the largest. However, the reduction of surface roughness in the end grinding process was the largest, which was 35.6%. For the removal of each phase of 2.5D Cf/SiC composites, the brittle fracture, fiber debonding, and breakage of the matrix could be reduced after applying ultrasonic vibration in both processing methods.