CVI过程中三向正交预制体孔隙结构的演变及气体扩散行为  

Evolution of pore structure and gas diffusion behavior of three-dimensional orthogonal preforms during CVI process

作　　者：肖佳文 杨敏[1] 姚彧敏 黄成杰 李红[1] 任慕苏[1] 孙晋良[1] XIAO Jiawen;YANG Min;YAO Yumin;HUANG Chengjie;LI Hong;REN Musu;SUN Jinliang(Composite Materials Research Center,Shanghai University,Shanghai 200444,China)

机构地区：[1]上海大学复合材料研究中心,上海200444

出　　处：《上海大学学报(自然科学版)》2025年第1期58-67,共10页Journal of Shanghai University:Natural Science Edition

摘　　要：为探究碳纤维预制体孔隙结构对碳/碳材料致密化效率的影响,以织造参数不同的3种三向正交预制体为研究对象,采用相同的化学气相渗透(chemical vapor infiltration,CVI)工艺致密化,并研究气体在纤维束内、纤维束间孔隙中的扩散行为,探究不同类型孔隙对增重速率的影响.借助ImageJ软件计算CVI后3种预制体中纤维束内规则化模型孔隙的演变;借助显微观测法获得预制体参数,定量计算模型孔隙通道面积及气体扩散系数.研究结果表明,气体在纤维束内孔隙中扩散时,前期发生Fick扩散,后期以Knudsen扩散为主,束内孔隙数量主要通过影响前期增重速率来影响孔隙填充;纤维含量低的A3预制体中束间孔隙率高,孔隙截面积大,具有更高的扩散系数,束内单丝按同心圆式排列,在CVI过程中易形成闭孔,气体在纤维束间孔隙处主要发生Fick扩散,扩散系数主要受扩散通道面积和孔隙率影响,并对后期增重速率产生影响.To investigate the effects of the pore structures of carbonfiber preforms on the densification efficiency of carbon/carbon materials,three types of three-dimensional orthogonal preforms with different weaving parameters were investigated.The same chem-ical vapor infiltration(CVI)process was used to densify and study the diffusion behavior of gas in the pores within and between thefiber bundles,and the effects of different types of pores on the weight gain rate were explored.ImageJ software was used to calculate the evolution of the regularized model pores within thefiber bundles in the three types of preforms following CVI.In addition,the pore channel area and gas diffusion coefficient of the model were quantitatively calculated using a microscopic observation method.The results indicate that when gas diffuses into the pores of thefiber bundle,Fick diffusion occurs in the early stage and Knudsen diffusion dominates in the later stage.The number of pores in the bundle affects the weight gain rate in the early stage,which in turn leads to porefilling.The A3 preform with lowfiber content has high inter-bundle porosity,a large-pore cross-sectional area,and a higher diffusion coefficient.The monofilaments inside the bundle are arranged in a concentric circle,which easily form closed pores during CVI.The gas mainly undergoes Fick diffusion in the pores between thefiber bundles,and the diffusion channel area and porosity affect the diffusion coefficient,which in turn affects the subsequent weight gain rate.

关 键 词：碳纤维预制体 孔隙结构 化学气相渗透 (chemical vapor INFILTRATION CVI) 致密化 气体扩散 

分 类 号：TB332[一般工业技术—材料科学与工程]