New study on ablation thermal/stress in fiber laser trepan drilling of 2.5D C/SiC composites based on numerical modeling and experimental analysis

Fiber laser drilling is crucial for micro-machining 2.5D C/SiC ceramic matrix composites. However, the process inherently induces ablation damage that severely compromises the mechanical performance and fatigue life of components. To address this critical challenge, this study established a new thermal-stress numerical model in fiber laser trepan drilling of 2.5D C/SiC composites. The model reveals intricate mapping relationships among the evolving temperature field, stress field, and ablation characteristics. By comparing experimental and simulated hole diameters, taper, and hole profiles, simulation errors were found to be less than 10%, validating the model's accuracy. Importantly, the results show that the temperature gradient fundamentally governs the ablation morphology of the fibers. At high temperature (2279-2705 K), the fiber exhibits a needle-like morphology, while at low temperature (1929-2279 K), they display a tapered end morphology. Furthermore, a linear relationship was demonstrated between fiber extrusion deformation and thermal stress distribution. Critically, this work identifies reduced laser scanning speed as an effective strategy to mitigate fiber extrusion damage. This study provides valuable insights and a predictive tool essential for achieving low-damage micro-hole machining in 2.5D C/SiC composites using fiber lasers.