Surface morphology on carbon fiber composites by rotary ultrasonic milling

Carbon-carbon composites (C/C composites) is typical high temperature resistant material. Therefore it is applied in solid rocket motor (SRM) throat mostly. Because the throat is mostly single piece and mini-batch, which is not suitable for mold forming. Usually, numerical control machining is still the main method. Due to high strength and heterogeneous composites, the machining damage defects are obvious and quality is poor. Thus, from the perspective of C/C composites ablation resistance, rotary ultrasonic machining technology effect on C/C composites surface defects and damage is investigated. Moreover, the influence of ultrasonic vibration on fiber cutting angle and machined surface morphology is analyzed. Meanwhile, based on comparative experiment, fiber pull-out length and surface porosity are presented as characterization parameters. The results show that ultrasonic vibration not only improves fiber cutting angle effectively, but also reduces pores and cracks on machined surfaces. Moreover, it reduces fiber pull-out length by 10%–50% numerically when along fiber milling. When fiber is perpendicular to the cutting direction, the pull-out length becomes shorter. The above study provides a theoretical basis for subsequent machined damage influence on ablation resistance of C/C throat.