基于酚醛树脂的碳/碳复合材料在高温分解过程的微结构演变

采用热压成型方法制备碳/ 酚醛树脂预制体, 再经高温碳化得到开气孔率为27 %、密度约1. 27 g/ cm3并具有预期孔隙结构的碳/ 碳复合材料。研究了200～900 ℃预制体转化为碳/ 碳复合材料过程中, 材料的密度、开气孔率、失重率、以及内部微观结构随温度的变化。分析了材料在高温分解过程中微观结构演变规律。结果表明,酚醛树脂主要在400～700 ℃大量分解, 其分解速率约为其余温度范围的4 倍, 该温度范围失重率增加了14 %、开气孔率增加了18 %。在高于400 ℃时形成大量裂纹与孔隙, 随着温度升高裂纹增多并进一步扩展, 900 ℃碳化后形成一种连通的特征性微观裂缝网格模式。高温分解后碳/ 碳复合材料中总孔容约0. 17 cm3 / g , 其中81 %的孔隙半径在122. 190～2. 440μm 范围内。 

Microstructural evolution of phenolic resin-based carbon/ carboncomposites during pyrolysis

The carbon/ carbon (C/ C) composites within the mat rix-crack microst ructure were prepared by pyrolyzing carbon fiber/ phenolic resin composite which was compacted by hot pressing. The material density of C/ C composites was about 1. 27 g/ cm3 , and the open porosity was 27 % af ter pyrolysis at 900 ℃. The alterations of density ,open porosity and mass loss during pyrolysis from 200 ℃to 900 ℃were investigated. The microst ructural evolutionof phenolic resin2based C/ C composites during pyrolysis was analyzed. The phenolic resin mainly decomposed f rom400 ℃to 700 ℃, and the decomposition rate was 4 times that of other temperature ranges. A high amount of regularly spaced segmentation cracks formed above 400 ℃, and further increased and expanded with elevated temperature. A microscopic network of the characteristic interconnecting crack pattern within C/ C composites was developed af ter pyrolysis at 900 ℃. The total pore volume of C/ C composites was 0. 17cm3 / g , and 81 % of the poreswere in the radius range of 122. 190～2. 440μm.