| With the continuous improvement of the hypersonic vehicle speed, and the service flight environment is getting worse and worse, in order to ensure the aircraft flight safety and stability. Therefore, it is necessary to research on aircraft nose cone and other key hot end components of thermal protection. As the hot end of the hypersonic aircraft key structure, thermal structural nose in flight will face very severe aerodynamic heating, in order to ensure the overall performance of hypersonic aircraft, vehicle nose does not allow large deformation, Therefore, the thermal protective structure of aircraft nose must meet the requirements of the long time oxidation and ablation. Ultra-high temperature ceramic composites due to high temperature, oxidation ablation and other outstanding features, is one of best choices for the vehicle nose and other key hottest components. However, ultra-high temperature ceramic materials are difficult to densification and the intrinsic brittleness and other characteristics increased the difficulty of preparation and processing of high-performance thermal protection structural material. Therefore, to prepare thermal protection structural nose with ultra-high temperature ceramic materials, processing and related performance assessment is of great significance.In this paper, based on the thermal protection structural requirements of the aircraft nose cone and combined with nose service characteristics, we designed the front end of the back-end cylindrical hemispherical modular structure, with the help of ANSYS software to establish a model for the analysis of the nose cone thermal protection structural temperature field. The results showed that the highest temperature of the nose section and to select the nosecone thermal protection materials depending on the temperature field analysis.This article selected Zr B2-Si C-G ultra-high temperature ceramic composite material as a nose thermal structures component preparation system. Hot pressing sintering were used to sinter nose thermal structure material, so it can guarantee a dense material, and to maintain good mechanical properties. The effects of different parameters on Zr B2-20 vol.%Si C-G composite ceramic were studied, such as graphite content, sintering temperature and so on. The results showed that under 1900 ℃/30MPa/1h hot pressing conditions Zr B2-20 vol.%Si C-10 vol.%G overall performance is more excellent material, including flexural strength of 487 MPa, fracture toughness 6.2MPa.m1/2, the relative density 99.7%.This dissertation adopted the ELID grinding technology of the ceramic sintering material for the nose thermal protection structural components processing molding, and the thermal structure grinding surface roughness are orthogonal experiment, systematic analysis of the relationship between the grinding process parameters and surface roughness. Final grinding process to determine the best combination: size w40#, wheel speed 26.2m/s, grinding depth 0.005 mm, workpiece speed 35r/min. And using ultrasonic testing(UT) and X-ray inspection(RT) combined method to process non-destructive testing for thermal structure nose ultra-high temperature ceramic body, indicating that the content of microscopic pores of ceramics internal and surface is relatively small, this showed that the nose cone thermal structure material has excellent overall performance.The phenomenon for the antioxidant ablation of the Zr B2-20 vol.%Si C-10 vol.%G component materials were studied in detail. the ground assessment test results show that macroscopic morphology of the nose thermal protection structural ultra-high temperature ceramics materials is relatively intact and can maintain good integrity; no micro-cracks are showing a good antioxidant ablation performance. Combined with ultra-high temperature ceramics of thermal structure nose ground examination results were analyzed oxidation mechanism. |
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