预制体结构对平板炭/炭复合材料增密过程的影响

Effect of preform structure on densification process of plate C/C composites

以不同纤维体积分数(21%、26%、32%)、不同布毡质量比(3:1,2:1,1:1)的针刺整体毡为预制体,采用化学气相渗透法(Chemical vapor infiltration,CVI)制备平板炭/炭(C/C)复合材料,研究预制体结构对CVI致密化过程的影响。结果表明:随纤维体积分数增加,整体毡的增密速率及最终密度都逐渐减小;布毡比对增密速率及最终密度影响很小。材料网胎中热解炭圆壳厚度沿材料厚度方向呈内部小、两侧大的对称分布;增加纤维体积分数或增加布毡比,材料内部的热解炭增厚程度随之减小。纤维体积分数为21%的预制体最适宜采用CVI工艺进行增密,增密80 h密度达到1.69 g/cm3,热解炭生长均匀。

Using needle-punched felt with different fiber volume fractions of 21%,26% and 32% and mass ratios of cloth to mat of 3：1,2：1 and 1：1 as preform,C/C composites were manufactured by the method of chemical vapour infiltration（CVI）.The effect of preform structure on densification process by CVI was analyzed.Results show that the densification rate and the final density of composites decrease with the increase of carbon fiber volume fraction.The ratio of cloth to mat has little effect on densification rate and the final density.The distribution of circle shell thickness of pyrolytic carbon in mat of all materials is symmetrical smaller in the middle and bigger in the laterals.The thickness of pyrolytic carbon in the middle of materials decreases with the increase of fiber content or ratio of cloth to mat.The CVI process is optimum to densify the felt with fiber volume fraction of 21% whose final density is 1.69 g/cm3 after 80 h infiltration,the pyrolytic carbon growth is even.