Design of domain-limited CVI reactor for L-shaped C/C structure

New complex-shaped and thin-walled carbon/carbon (C/C) composites have become the main hot structural material for new hypersonic vehicles because of their superior properties. In the preparation of complex-shaped and thin-walled C/C composites by chemical vapor infiltration (CVI) method, problems such as slow density growth and inhomogeneity of density distribution have been hindering the development of C/C hot structure, in order to solve which, this paper proposes a design method for domain-limited CVI reactors for complex-shaped and thin-walled C/C structure, as well as conducts CVI experiments with the designed domain-limited reactor for a L-shaped and thin-walled C/C structure. A coupled multi-physical field model considering flow, diffusion, and chemical reactions was established, which was verified by comparison with experiments. The effects of diameter of hole, distance of neighboring holes, depth of hole and length of reactor on deposition quality were analyzed by simulation. The results showed that larger diameter of hole and smaller distance of neighboring holes would be more favorable for the accumulation of density of structure and depth of hole has little effect on deposition. The best solution is diameter of hole with 18 mm and distance of neighboring holes with 20 mm. Homogeneity of density can be improved by adjusting the specific length of the reactor. For the fabric sizes given in the study, when the specific length of the preform is 3.4, the deposition rate and homogeneity can reach a good level at the same time. This study is a guideline for optimization the quality of C/C structure during processing.