Micro-hole drilling of 2.5D C/SiC composite with picosecond laser: Numerical modeling and experimental validation on hole shape evolution

Micro-holes of 2.5D C/SiC composites produced by picosecond laser are widely used in aerospace, military, and automotive industries. An accurate numerical model is crucial to illustrate the formation mechanism of hole shape and ablation characteristics. This paper proposes a two-dimensional transient numerical model based on solid-liquid-gas coupling in micro-hole drilling of 2.5D C/SiC composites with a picosecond laser. In the stage of solid-liquid phase transition, original mass, energy, and momentum conservation equations are optimized by considering surface tension, gravity, and hydrostatic pressure. In the stage of liquid-gas phase change, the mass transfer during the material evaporation is considered and used as a source term to optimize the level set equation. The effectiveness of the proposed model is validated by picosecond laser micro-hole drilling experiments on 2.5D C/SiC composites. Compared with the existing research, the results show that the proposed can accurately depict hole shape evolution in picosecond laser drilling of 2.5D C/SiC composites, not only including entrance, exit diameter, and hole taper, but also the hole profile and its dynamic variation. In addition, the model effectively simulates the thermal effect phenomena, such as thermal damage, pressure concentration, and recast layer. And the thermal damage is found to be the main cause of the hole quality variation, which changes from severe to smooth along the hole entrance to exit. The research provides important support for high-quality micro-hole machining of 2.5D C/SiC composites with the picosecond laser.