【摘要】 采用化学气相沉积工艺对未处理和2 500℃热处理的炭纤维预制体进行致密化,对致密化后的C/C复合材料进行弯曲力学性能测试,借助偏光显微镜和扫描电子显微镜观察热解炭的组织、纤维的表面和弯曲试样断口的形貌。结果显示:高温热处理后,纤维表面变的更加光滑,表面出现很多沿纤维轴向的沟槽;致密化后的两种C/C复合材料的基体消光角约为21°,均为高织构热解炭;与未处理纤维增强C/C复合材料相比,经高温热处理后纤维增强的C/C复合材料的弯曲强度和模量均大幅下降,断裂特征由脆性转变为典型的假塑性,断口处有大量纤维拔出,纤维表面未粘附热解炭,表明对纤维进行高温热处理显著降低了纤维和热解炭基体的界面结合强度,导致材料强度降低,断裂呈假塑性。更多还原

【Abstract】 Untreated and 2 500 ℃ heat treated carbon fiber felts were densified by chemical vapor infiltration.The mechanical properties of the as-prepared carbon/carbon(C/C) composites were examined by three point bending test.Furthermore,texture of the pyrolytic carbon,surface morphology of carbon fibers and fracture surface morphology of the broken samples were observed by polarized microscopy and scanning electron microscopy.The results showed that after the high temperature heat treatment,the surface of the fibers became smoother and numerous grooves can be observed.The matrix of the both deposited C/C composites had an extinction angle of about 21°,indicating it was a high textured pyrolytic carbon.Compared with the untreated carbon fiber felt reinforced C/C composite,the high temperature treated carbon fiber felt reinforced C/C composite had a sharp decrease in flexural strength and modulus,and its failure exhibited a typical pseudo plastic mode.It cannot be found pyrolytic carbon wrapping the pulled-out fibers which illustrated that the heat treatment significantly weakened the fiber-matrix interface resulting in the low mechanical properties and pseudo plastic failure of the C/C composites.更多还原