## 6 Conclusions  
In this study, the thermal shock resistance and structural integrity of carbon fiber-reinforced pyrolytic carbon composites, coated with a silicon carbide gradient layer, were evaluated under thermal shock conditions (2173 K and 3 thermal shock cycles) using a CFEM approach and ML model. The key conclusions are as follows:  
1. Macroscopic thermal shock simulations indicate that microstructural organization plays a crucial role in thermal shock resistance. After three cycles at 2173 K, the incorporation of carbon fibers significantly enhances the mechanical performance of the coating, preserving both strength and structural integrity.
2. Our simulation results reveal that the porous carbon layer remains the weakest link in terms of mechanical performance, with a higher risk of coating delamination under thermal cycling. Improving the mechanical properties of the porous carbon layer is recommended.
3. Parametric analysis shows that fiber content has the most pronounced effect on the coating's overall performance. Higher fiber content leads to superior thermal shock resistance.
4. The coating demonstrates better thermal shock resistance at a thickness of 100 \(\upmu\)m. However, the improvement over 20 \(\upmu\)m is marginal, and performance deteriorates at 60 \(\upmu\)m.
5. A dense, void-free coating provides optimal thermal shock resistance for both the transition layer and substrate. Given the porous carbon substrate's susceptibility to damage, the A\({}_{1}\)B\({}_{3}\)C\({}_{3}\) configuration (void-free, 100 \(\upmu\)m thickness, and 60% fiber content) is recommended to enhance the overall resistance to thermal shocks. Additionally, since the interfaces between the coating and transition layer, as well as between the transition layer and substrate, are prone to damage, minimizing compositional differences across these interfaces is advised to further improve thermal shock resistance.
6. ML further supports the findings by identifying fiber content, porosity, and coating thickness as critical factors influencing thermal shock resistance. The ML models successfully predict the material behavior under thermal shock, allowing for the efficient design of coatings with enhanced performance, thus reducing the need for extensive experimental trials.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app142311025/s1](https://www.mdpi.com/article/10.3390/app142311025/s1)]([https://www.mdpi.com/article/10.3390/app142311025/s1](https://www.mdpi.com/article/10.3390/app142311025/s1)).  
Methodology, Y.X.; Software, Q.D.; Validation, J.C. and Z.S.; Investigation, Z.D.; Resources, J.X.; Data curation, H.Q.; Writing--original draft, Q.D., Y.X. and Z.D.; Visualization, Q.Z.; Supervision, C.P., Z.L. and K.G.; Funding acquisition, Z.L. and K.G. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Defense Industrial Technology Development Program (Grants No. JCKY2021130B0007), Major basic research projects on equipment (Grant No. 909010106301), Guangdong Basic and Applied Basic Research Foundation (Grant No. 2023A1515012156 and 2024A1515011656), \"Pioneer\" and \"Leading Goose\" R&D Program of Zhejiang (No. 2024 SSYS0085) and Science and Technology Planning Project of Guangzhou City, China (No. 202201010739). And The APC was funded by \"Pioneer\" and \"Leading Goose\" R&D Program of Zhejiang (No. 2024 SSYS0085).  
**Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors on request.  
**Conflicts of Interest:** Authors [PERSON], [PERSON], [PERSON] and [PERSON] were employed by the company Central Iron and Steel Research Institute and Gaona Aero Material Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.