Numerical and experimental study on the amplitude effect of ultrasonic vibration-assisted milling of 3D needle-punched Cf/SiC composite

The anisotropy, heterogeneity, and high hardness of C f /SiC composite bring great difficulties to its efficient and high-quality processing. Ultrasonic vibration-assisted milling (UVAM) has been shown to positively affect the machining quality of C f /SiC. This work focuses on the effect of ultrasonic amplitude on 3D needle-punched C f /SiC composites machining under different fiber cutting angles, and few related studies have been reported. By analyzing the simplified cutting model for both forward and reverse cutting, the influence of ultrasonic amplitude on tool-fiber contact characteristics was investigated. Under fiber cutting angles of 0°, 45°, 90°, and 135°, finite element simulations based on the orthogonal cutting model and UVAM experiments with different amplitudes were performed. The results showed that the alternating friction force caused by the harmonic vibration promoted the damaging effect of the tool on the fiber and SiC matrix. At 0° and 135°, localized fiber failure occurred early. And at 45° and 90°, the shear failure of the fiber was strengthened, which alleviated the damage to the low-strength matrix and the interface layer. Compared with conventional milling, the resultant force showed a downward trend, and typical defects such as pits, fiber pullout, matrix voids, and interface debonding on the machined surface were suppressed in UVAM. As the amplitude increased, the machined surface became smoother, and the surface roughness Sa at all angles decreased by more than 30%. According to the response surface method, the influence order of machining parameters on Sa was obtained: feed rate > amplitude > cutting speed. Sa predictive regression model with only a 5% deviation from the experimental value has good accuracy and reliability. This work shows that reasonable control of ultrasonic parameters and fiber cutting angle in UVAM significantly affects the machining quality improvement of 3D needle-punched C f /SiC components.