Densification and Texture Control in Carbon Fiber/Carbon Composites by Pressure Carbonization

采用压力碳化技术，研究了碳纤维/碳复合材料（C/C复合材料）中基体的致密化和织构控制过程。目前的工作包括三个部分；(1)商用C/C复合材料基体裂纹扩展的研究；(2)压力对沥青与酚醛树脂相互作用的影响，以及对合成碳织构的影响；(3)采用两种不同的前驱体和压力碳化法制备C/C复合材料的初步研究。在偏光显微镜下观察了C/C复合材料的裂纹扩展。C/C复合材料的基体织构决定其力学性能。良好的镶嵌织构是减缓变质裂纹扩展和获得高韧性C/C复合材料的关键。通过在沥青中掺入聚对苯二甲酸乙二醇酯（PET）或苯酚树脂，可以控制C/C复合材料基体中光学单元的大小。随着添加剂（PET或酚醛树脂）用量的增加，基体的织构通过中马赛克和精细马赛克织构，从粗马赛克到各向同性不断变化。在压力作用下，这两种前驱体的相互作用加速，得到了具有均匀光学织构的基体。在目前的工作中，由于所用的高压灭菌器尺寸有限和前驱体反复浸透的困难，我们无法获得足够高的密度和大尺寸的复合材料来研究其断裂行为。然而，我们可以通过混合两种不同的前驱体和在压力下碳化来确定碳纤维/碳复合材料获得高密度和控制基体织构的可能性。

By using pressure carbonization technique, the processes for densification and texture control of the matrix in carbon fiber/carbon composites (C/C composites) were investigated. The present work consisted of three parts; (1) the study on crack propagation in the matrix of a commercial C/C composite, (2) the study on the pressure effect on the interaction between pitch and phenol resin, and also on the texture of resultant carbons, and (3) the preliminary production of C/C composites by using two different precursors and by pressure carbonization.The crack propagation in a C/C composite was observed under polarized liaht microscope. The texture of the matrix of C/C composite was shown to govern its mechanical properties. A fine mosaic texture of the matrix was suggested to be essential for slowing down the propagation of deteriorative crack and for getting high toughness of the C/C composite.The size of optica units in the matrix of C/C composites was found to be controlled by mixing either polyethylene terephthalate(PET) or phenol resin into pitch. With increasing the amount of additives (PET or phenol resin), the texture of the matrix changed continuously from coarse mosaic to isotropic through medium and fine mosaic textures. The interaction between these two precursors was accelerated under pressure and the matrix with homogeneous optical texture was obtained.In the present work, we could not have the composites with sufficiently high density and large size for studying on their fracture behavior because of the limited size of the autoclave used and the difficulty of repeated precursor impregnation. However, we could confirm the possibility for carbon fiber/carbon composite to get high density and also to control the texture of the matrix by mixing two different precursors and by carbonization under pressure.