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To address the urgent demand to test mechanical/thermal/oxidation key performance parameters for new ultra-high-temperature structures, a radiation thermo-mechanical joint test system that can perform fracture performance tests under an extremely high temperature oxidation environment (1500 °C) was designed and implemented. Key performance parameters, such as the fracture strength and time to failure of high-temperature-resistant C/SiC composite structure, were tested and measured in oxidation environments up to 1500 °C. In present test, when the temperature rises from 1000 °C to 1500 °C, the fracture load of C/SiC structure decreased by 47.5%, and the time to failure reduced to 50.1% of that at 1000 °C. This extremely high temperature load test system provides an important thermo-mechanical joint test technique to study the mechanical properties of structure and material for hypersonic aircraft under an oxidation environment. The test shows that a high-temperature preload significantly enhances the fracture strength of C/SiC composite structure. In present work, the fracture strength increases by 38% and the time to failure increases by 61.1% for C/SiC. The test results can be used to improve the safety, reliability, and strength of composite components of hypersonic aircraft under extreme thermal environments.

Because hypersonic vehicles face environments with extremely high temperatures in which the vehicles׳ outer shells experience single-sided heating and the temperature varies nonlinearly over time, a self-designed radiation and one-sided heating test apparatus is established in this paper, which can perform the thermal insulation performance test for lightweight ceramic thermal protection materials of hypersonic aircraft in extremely high-temperature/oxidation environments up to 1700 °C. Meanwhile, experimental research on thermal insulation performance of a lightweight ceramic material specimen and a novel ceramic-nanomaterial hybrid structure in high-temperature/oxidation environments up to 1700 °C was carried out. Different materials alone and in combination were analyzed and compared to select the most effective insulation scheme. It is found that the thermal insulation performance of the ceramic-nanomaterial hybrid thermal protection structure can be increased approximately 50% compared with that of the lightweight ceramic material specimen. Additionally, non-linear time-varying thermal environments with extremely high temperatures were generated and the thermal insulation performance tests were performed in this paper. The present work provides an important test method for the thermal protection design of hypersonic aircraft through the establishment and application of an extreme high-temperature/oxidation test system which can create one-sided heating, time-varying thermal environments.

Lightweight insulation materials are widely used to thermally protect high-speed aircraft, such as missiles. Thermal conductivity is an important parameter used to evaluate the efficiency of a material’s thermal insulation performance. Since thermal conductivities provided from material handbooks or manufacturers are discrete data for different temperature ranges, there is a deviation between those and actual parameters in terms of continuous nonlinear variations. Therefore, this study measures the thermal conductivities of lightweight thermal insulation materials at high temperatures, and the relationship between the thermal conductivity and temperature is obtained. A finite element model of the thermal insulation materials is also established and applied to numerically calculate the thermal insulation properties for high-temperature ceramic fiber insulation materials using the experimentally obtained nonlinear relationship between thermal conductivity and temperature. Additionally, a transient aerodynamic heating experiment simulation system is used to thermally test the same materials; the calculated and experimental results for the same materials are compared, which exhibit good consistency that demonstrates that accurate results can be obtained from the numerical computation using the relationship established from the experimentally measured conductivity and temperature.

Transient aerodynamic heating experiments with high-speed aircraft require temperature sensors that can carry out rapid and accurate electromotive force (EMF)–temperature conversions. A fast, high-precision non-linear EMF–temperature conversion method is proposed. In this method, the temperature values to be converted were pre-positioned using a non-linear mathematical model. Then, they were accurately positioned using an efficient binary search algorithm with a small scope. Thus, this method has rapid conversion speed and high calibration precision. This conversion precision is enhanced by one order of magnitude over that of the normal reference table, and the conversion time is 1% of that of the traditional piecewise linearization method. This method was employed in a transient aerodynamic heating experimental simulation system with high-speed aircraft. The experiment results show that, in the case of a high change rate of temperature and heat flux, accurate dynamic tracking can still be realized, and the experimental simulation results agree well with the pre-set environment. The developed temperature sensor calibration method is necessary for high-speed and high-precision aerodynamic heating experiments with hypersonic aircraft.

The randomization of deterministic fatigue damage equation leads to the stochastic differential equation and the Fokker-Planck equation affected by random fluctuation. By means of the solution of equation, the probability distribution of fatigue damage with the change of time is obtained. Then the statistical moment of fatigue life in consideration of the stationary random fluctuation is derived. Finally, the damage probability distributions during the fatigue crack initiation and fatigue crack growth are given.