The strong anisotropy of the 3D braided C/SiC composite materials exists.In addition, Property data in each direction is insufficiently accumulated and the composite strength prediction method has not been well developed. In order to identify problems in the application of ramjet nozzle made of the 3D braided C/SiC composite material, and to find the corresponding solutions, strength prediction and experimental research were carried out for the ramjet nozzle. Composite nozzles ruptured under low pressures in the pressure test were analyzed so as to find reasons and solutions for the early failure. The results showed that the C/SiC nozzle throat was of low density, resulting in low strength and weak bearing capability, which was the local destruction reason for the first strength verification test. In order to improve the strength of the nozzle, it needs to be ensured that the throat deposition density should be above 1.9g/cm3by design and control of the deposition flow field parameters according to the geometry of the nozzle. The improved nozzle was verified by the experiment.The experimental and the calculation results were basically consistent,and it meets the requirements. To ensure the even distribution of the nozzle density, density distribution of the nozzle throat and longitudinal directions should be non-destructively tested using industry CT.
