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连续纤维增韧的碳化硅复合材料(以下简称C/SiC),作为超高速飞行器热结构使用时,有可能在高温环境下受到高速撞击的作用,因此,掌握其在极端环境(高温、高应变率)下的力学性能是进行结构安全设计的基础。本文采用具有高温实验能力的分离式Hopkinson杆,在293~1273K温度范围内进行了动态压缩力学性能测试,研究了环境温度和加载速率对材料力学性能的影响。结果表明:C/SiC复合材料的高温压缩力学性能主要受应力氧化损伤和残余应力的共同影响。实验温度低于873K时,应力氧化损伤的影响很小,而由于增强纤维和基体界面残余应力的释放使界面结合强度增大,复合材料的压缩强度随温度的升高而增大;当实验温度高于873K时,应力氧化损伤加剧,其对压缩强度的削弱超过残余应力释放对强度的贡献,材料的压缩强度随温度的升高逐渐降低。由于应力氧化损伤受应变率的影响很大,当温度由873K升高至1273K时,高应变率下压缩强度降低的程度要比应变率为0.0001/s时低得多。
Continuous fiber-reinforced silicon carbide composites (hereinafter referred to as C / SiC), when used as a thermal structure of a superhigh-speed aircraft, may be subjected to high-speed impact in a high-temperature environment. Therefore, Rate) under the mechanical properties of structural safety design is the basis. In this paper, the dynamic Hopkinson bar with high temperature experimental capability was used to test the dynamic mechanical properties at 293 ~ 1273K. The effects of ambient temperature and loading rate on the mechanical properties of the material were studied. The results show that the mechanical properties of C / SiC composites at high temperature are mainly affected by stress oxidation damage and residual stress. When the experimental temperature is lower than 873K, the effect of stress oxidation damage is small. However, the compressive strength of the composites increases with the increase of temperature due to the release of residual stress at the interface between the reinforcing fibers and the matrix, Above 873K, the stress oxidation damage aggravated, and its weakened compressive strength exceeded the contribution of residual stress release to the strength, and the compressive strength of the material decreased with increasing temperature. As the stress oxidation damage is greatly affected by the strain rate, when the temperature is increased from 873K to 1273K, the compressive strength decreases at a high strain rate much lower than when the strain rate is 0.0001 / s.