低温对碳纤维复合材料弯曲性能影响试验研究

由于航天运载器的轻量化需求，高性能碳纤维增强环氧树脂基复合材料(CFRP)已经应用于液体燃料贮箱的研制，但其服役环境苛刻，往往要经受-183~-253 ℃的超低温或多次低温循环过程．目前，对CFRP的低温力学性能，尤其是常-低温循环力学性能的研究仍比较局限，这制约了CFRP燃料贮箱的设计和研制进程．本文针对一种液氧相容的环氧树脂体系，采用热压罐工艺制备了CFRP单向板，并测试其在25 ℃、-55 ℃、 -120 ℃和-183 ℃下的弯曲力学性能．结果表明，弯曲强度和模量均随着温度降低而提高，当温度从25 ℃降低到-183 ℃时，弯曲强度提高约66.7 %，弯曲模量提高约10.3 %．同时，本文也研究了室温-液氧循环50~200次对弯曲力学性能及微裂纹萌生的影响．结果表明，200次循环后，单向板的弯曲强度基本没有降低，并且内部也无微裂纹产生．本文研究表明，该CFRP体系具有较为优异的低温力学性能和耐低温循环性能，在液体燃料贮箱领域有着巨大应用潜力．

Influence of Low Temperature on the Flexural Properties of Carbon Fibrous Composites

Due to the lightweight requirement of the launch vehicles, high-performance carbon fiber reinforced epoxy composites (CFRP) have already been used in the construction of the liquid propellant tanks. The service environment of CFRP is complex, usually facing low temperature of -183~-253 ℃ or even multiple low-temperature cycles. To date, related research about the low temperature performance, especially the low-temperature cycling performance of CFRP, is still very limited, which restricts the design and development of CFRP fuel tanks. In this paper, a liquid oxygen compatible epoxy resin system was used to prepare the CFRP unidirectional laminates through the autoclave process. The flexural mechanical properties at 25 ℃、-55 ℃、-120 ℃ and -183 ℃ were tested. The results show that both the flexural strength and the modulus increase with decreasing the temperature, and the flexural strength and modulus are respectively increased by 66.7 % and 10.3 % when the temperature is decreased from 25 ℃ to -183 ℃. Moreover, the effects of 50~200 cycles from room temperature to -183 ℃ on the flexural mechanical properties and the microcrack initiation were also explored. The results show that the performed 200 cycles have nearly no effects on the flexural strength of the unidirectional laminates, as well as on the generation of cracks. The study reveals that the CFRP system has outstanding low temperature mechanical properties and low-temperature cycling resistance, and thus has great application potential in fuel tanks.