3D C/C复合材料的热膨胀性能

The thermal expansion behavior of 3D C/C composites

通过测定热膨胀系数(CTE),分析了不同密度以及高温处理前后热解炭基三维编织炭/炭复合材料(3DC/C复合材料)的热膨胀行为,并与PAN基炭纤维以及热解炭的热膨胀性能作了比较。结果表明:PAN基炭纤维在1200℃以后,出现明显的负膨胀。从室温到100℃,C/C复合材料呈负膨胀状态,CTE与密度成正比;从100℃到1000℃,C/C复合材料的CTE-温度曲线基本遵循热解炭基体的热膨胀规律变化;超过1000℃以后,CTE-温度曲线出现峰值,表明热解炭的膨胀受纤维的限制。复合材料的热膨胀行为由纤维和基体二者决定。

Three dimensional braided carbon/carbon composites （3D C/C composites） were fabricated by chemical vapor infiltration. The thermal expansion behavior of these materials with various densities before and after heat treatment was investigated. It is found that PAN-based carbon fibers （CFs） have an obviously negative coefficient of thermal expansion （CTE） after heat treatment at 1 200 ℃. The CTE of the 3D C/C composites is negative from room temperature to 100 ℃ and is proportion to their density. In the temperature range of 100-1 000 ℃,CTE vs. T curves have an almost a constant slope and expansion behavior of the composite is similar to that of pyrocarbon. When the temperature is above 1 000 ℃,a peak is found in the CTE vs. T curves,indicating that expansion of the pyrocarbon is limited by CFs and the thermal expansion behavior of the composites is determined by both CFs and matrix.