ICVI工艺参数对碳/碳复合材料快速均匀致密化的影响

Effect of ICVI process parameters on the rapid and uniform densification of Carbon/Carbon composite

为了研究碳/碳(C/C)复合材料的快速均匀致密化工艺,参考工业天然气的成分,以92%甲烷(CH4)、5%乙烷(C2H6)、3%丙烷(C3H6)组成的混合气作为前驱体,在沉积温度为1075℃时,采用等温化学气相渗透(ICVI)工艺,在不同系统压力和滞留时间下对16和26 mm两种厚度的碳纤维针刺预制体进行120 h致密化,制备C/C复合材料。对制备出的C/C复合材料进行轴向和径向切割取样,利用多功能密度测试仪研究压力和滞留时间对C/C复合材料致密化速度和均匀性的影响。结果表明:沉积温度为1075℃,滞留时间为1.0 s时,20 kPa下,经过120 h致密化后,16和26 mm厚度的C/C复合材料平均密度分别为1.45和1.43 g/cm3,较10 kPa压力下的平均密度(1.06和0.91 g/cm3)有明显提高,且厚度对C/C复合材料密度均匀性的影响减小。沉积温度为1075℃,压力为20 kPa时,将滞留时间降低到0.1 s,经过120 h致密化后,16和26 mm厚度的C/C复合材料平均密度均达到1.7 g/cm3以上,厚度对前驱气体在预制体内渗透效果的限制作用非常小;并且,在此实验条件下制备出沿气流方向密度均匀性比较理想的C/C复合材料。基于热解碳沉积反应机理,利用COMSOL软件对不同ICVI条件下C/C复合材料进行了致密化过程的数值模拟分析,模拟结果与实验中获得的C/C复合材料的致密化效果具有较高的一致性。

In order to study the rapid and uniform densification process of Carbon/Carbon(C/C)composites,referring to the composition of industrial natural gas,a mixture of 92%methane(CH4),5%ethane(C2H6)and 3%propane(C3H6)was used as the precursor for the densification of C/C composites.At the deposition temperature of 1075℃,the carbon fiber needled punched preforms of 16 mm and 26 mm in thickness were densified for 120 h by isothermal chemical vapor infiltration(ICVI)process under different system pressures and residence times to prepare C/C composites.The influence of pressure and residence time on the densification rate and uniformity of C/C composites was studied by multi-functional density tester.The results show that the average density of 16 mm and 26 mm thickness C/C composites was 1.45 g/cm3 and 1.43 g/cm3 respectively after 120 h densification at 1075℃and 1.0 s residence time,which is significantly higher than that at 10 kPa(1.06 g/cm3 and 0.91 g/cm3),and the thickness had little effect on the density uniformity of C/C composites.When the deposition temperature was 1075℃and the pressure was 20 kPa,the residence time was reduced to 0.1 s.After 120 h of densification,the average density of 16 mm and 26 mm thickness C/C composites was over 1.7 g/cm3,and the thickness had little effect on the permeability of precursor gas in the preform.Under the experimental conditions,C/C composites with ideal density uniformity along the air flow direction were prepared.The densification process of C/C composites under different ICVI conditions was simulated and discussed by numerical simulation using COMSOL software,which is consistent with the obtained experimental results.