超低温对T700碳纤维/环氧复合材料弯曲性能的影响

研究正交铺层的碳纤维增强环氧树脂基复合材料（CFRP）在超低温的环境下的弯曲性能和损伤破坏形式。对复合材料试样进行不同时间的液氧浸泡处理和不同次数的常温/液氧温度热循环处理来模拟液氧燃料贮箱使用工况，通过配有超低温试验装置的力学试验机研究CFRP在不同超低温条件处理前后的低温弯曲强度和弯曲模量的变化规律；采用扫描电子显微镜（SEM）对破坏前后试样的微观形貌进行分析。结果表明，经过液氧浸泡及常温/液氧温度热循环处理的CFRP的超低温弯曲强度和模量变化趋势基本一致，均随时间和循环次数的增加先下降后上升，这种变化规律与其超低温环境下材料的微观结构变化密切相关。结合CFRP破坏前后的宏观和微观结构特性以及微裂纹的扩展规律，揭示了正交铺层CFRP超低温弯曲性能变化的 机理。

Influence of Cryogenic Temperature on Bending Properties of A T 700 Carbon Fiber/Epoxy Composite

The bending properties and damage mechanism of the cross-ply laminates of the carbon fiber reinforced plastics (CFRP) at cryogenic temperatures（-183℃）are investigated using a low temperature experiment device. The composite samples are immersed in liquid oxygen for different time and cycled in room temperature/ cryogenic temperature for distinct times to simulate the actual conditions of the liquid oxygen tank. Micro-morphologies and structures of the damaged composite specimens after different cryogenic temperature treatments are observed by scanning electron microscope(SEM). The results show that the flexural strength and flexural modulus of the treated specimens have the same variation trend. They first fall and then rise with the increasing immersing time and cycle index respectively. The variation of flexural strength and flexural modulus after different cryogenic temperature treatments are investigated, which are related to the microstructure change of composite at the cryogenic temperature. Combined with the macroscopic and microscopic structural characteristics of the damaged specimens and the law of the micro-cracks′ extension, the damage mechanism of bending properties of the composite at cryogenic temperature is revealed.