Research On Thermo-Mechanical-Coupled Properties Of Metallic Honeycomb Structure Of High-Speed Vehicle

The hypersonic vehicle is already concerned by military power countries in the world, it will greatly changed the future military science and technology and have revolutionary consequences for the war. Metal thermal protection system (MTPS) has become the first choice for reusable launch vehicle (RLV) and high-speed vehicle as a widespread passive thermal protection system in sub-high-temperature (below 1000℃) area, it has some predominant advantages such as large-size, reusability, and low cost in the whole life period. MTPS consists of three parts basically:High-Temperature alloys honeycomb panel structure, integrated insulation structure and coating connecting structure. Presently, the insulation capability of the MTPS is much less than the performance requirements of the high-speed vehicles which faces ultra-high heat and long hypersonic cruise thermal environment. To improve the performance of the MTPS, introduction phase change materials (PCM), the response of MTPS under thermo-mechanical-coupled condition was analyzed. The main contents were respectively presented as follows.With the thermal environment of the MTPS, two typical phase change materials is introduced, by changing the PCM's position in the vertical direction under the principle of thickness and basic structure invariable, the thermal analysis of the development MTPS is completed. It is found that the high-temperature PCM make very small effect to improve the insulation ability, and will decrease the insulation ability when it is at a inappropriate position. On the contrary, the insulation ability of the MTPS improved by the low-temperature PCM improved significantly. The effect of PCM it directly related to the heat flux where is the PCM placed, the insulation ability will get better when the heat flux became lower. The PCM's energy storage density and thermal conductivity is the other two important factors related to the insulation ability of the TPS.Base on the optimal solution of the improved MTPS previously obtained, the influence of side panel, bracket and gap on unheating surface's temperature was analysised. For the development and function of the bracket, select the Z-shaped box bracket structure, the local calibration model is build to the heat concentration problem calculation. Change the angle of declination of the Z-shaped bracket will get a certain extent improve to the thermal performance. For the short heat path, the heat concentration problem caused by the gap is more seriously. By the results, the heat concentration problem of the improved MTPS is much better than the traditional MTPS, but it also should focus on to the designers. The possibility to improve the thermal performance of the improved MTPS by change the structure and layout of the side panel, bracket and gap or using load-bearing PCM coating structure is also discussed.Finally, the temperature field, displacement field and stress field of the typical structure of MTPS under thermo-mechanical-coupled load were computed by finite element method. As the full structure has good plane symmetry, it is feasible to analysis one fourth of the full structure. The indirect method of thermal-structure coupling was used. The proposed model was used to analyze the improved MTPS under the simplified reentry thermo-mechanical-coupled load of X-33 space areoplane. The max temperature of the bottom of MTPS is higher than the previously result by the two side panel and bracket coupled influence. The metal honeycomb sandwich panel and the metal connecting structure were the main mechanical load bearing components, the stress concentration phenomenon was appear around the upper position of the metal connecting structure. The maximum elongation of the MTPS structure is 0.78mm, while the maximum equivalent stress is 31.5MPa, which is far smaller than the yielding limit of Haynes214. The results showed that this type of MTPS can satisfy the service requirement, and the thermal and structure performance potential for improvement of this MTPS will satisfy the requirements of the future spacecraft.