中文摘要：

采用场发射扫描电子显微镜、广角X射线衍射、元素分析、高分辨透射电子显微镜对东丽T700S、T700G和东邦UT500 3种碳纤维的表面和断面形貌、化学组成及石墨微晶等微观组织结构进行了表征,比较了这3种碳纤维的微观结构差异,并分析了这些差异对力学性能的影响。结果表明,T700G碳元素含量较高,氮元素含量较低,它的石墨微晶尺寸较大,取向度较高,这是它比T700S拉伸模量高但断裂伸长率低的原因;UT500的表面结构与断面结构不如T700S和T700G好,微晶尺寸也较小,但它的直径略细,而且石墨微晶内（002）晶面排列比T700S和T700G更规整,导致UT500的综合力学性能略优于T700S和T700G。

英文摘要：

Field emission scanning electron microscope, X-ray diffractometer, elemental analysis and high-reso- lution transmission electron microscope were used to characterize the surface and fracture feature, chemical composition and graphite microcrystalline structure of three kinds of carbon fibers including Toray T700S, T700G and Toho UT500. The microstructure differences of the three carbon fibers were compared and the effects of these differences in mierostructure on mechanical properties of carbon fiber were analyzed. Rustles showed that TT00G has a higher carbon content and a lower nitrogen content, larger graphite crystallite size and orientation degree, which are the reasons that it has higher tensile modulus but lower elongation at break than T700S; surface and fracture feature of UT500 were slightly worse than T700S and T700G and its graphite crys- tallite size is smaller; however, the diameter of UT500 is a little thinner and the （002） crystal faces in graphite microcrystalline arrange more ordered than TT00S and TT00G, which cause the comprehensive mechanical prop- erty of UT500 is a bit better than that of T700S and T700G