PAN基碳纤维微晶结构对拉伸强度的影响

Effect of Crystallites Structure of PAN-based Carbon Fibers on Tensile Strength

碳纤维由微晶和非晶碳所构成。利用X射线衍射(XRD)和拉曼光谱(Raman)研究聚丙烯腈(PAN)基碳纤维微晶结构对拉伸强度的影响机理。结晶度、石墨化程度、微晶无序化程度、微晶尺寸都对拉伸强度有显著影响。结晶度、石墨化程度越大,微晶无序化程度越小拉伸强度越大。微晶尺寸越大拉伸强度越小。比较T300和T700,结晶度、石墨化程度的增加,微晶无序化程度的减小所导致的拉伸强度增量大于微晶尺寸增加所导致的拉伸强度减小量,从而使得T700的拉伸强度大于T300的拉伸强度,同理可知T800的拉伸强度大于T700的拉伸强度。比较M35J和M40J,结晶度、石墨化程度的增加,微晶无序化程度的减小所导致的拉伸强度增量小于微晶尺寸增加所导致的拉伸强度减小量,从而使得M40J的拉伸强度小于M35J的拉伸强度,同理可知M46J的拉伸强度小于M40J的拉伸强度。M35J,M40J和M46J内的较大的微晶对拉伸强度的影响起决定性作用。

Carbon fiber is composed of crystallite and amorphous carbon.The X-ray diffraction(XRD)and Raman spectroscopy were used to investigate the influencing mechanism of the microstructure of crystallites of polyacrylonitrile(PAN)-based carbon fibers on tensile strength.The results show that the crystallinity,the degree of graphitization,the degree of crystallites structural disorder and the crystallite size have obvious effects on tensile strength.The larger the crystallinity and the degree of graphitization,the larger the tensile strength;the smaller the degree of crystallites structural disor-der,the larger the tensile strength;the larger the crystallite size,the smaller the tensile strength.Comparing T300with T700,the increment of tensile strength,which is caused by the increase of the crystallinity and the degree of graphitization,and the decrease of the degree of crystallites structural disorder,is larger than the decrement of tensile strength,which is caused by the increase of the crys-tallite size.Therefore,the tensile strength of T700is larger than that of T300,and the same with that the tensile strength of T800is larger than that of T700.When M35J is compared with M40J,the increment of tensile strength,which is caused by the increase of the crystallinity and the degree of graphitization,and the decrease of the degree of crystallites structural disorder,is smaller than the decrement of tensile strength,which is caused by the increase of the crystallite size.Therefore,the tensile strength of M40J is smaller than that of M35J,and the same with that the tensile strength of M46J is smaller than that of M40J.In M35J,M40J and M46J,the bigger crystallite size is a crucial factor that affects the tensile strength.