Microstructure Characterization And Property Analysis Of T800 Carbon Fibers And Graphite Fibers

High performance carbon fiber,the key material in the field of aerospace,is widely used in the construction of national defense economy,because its light weight,high strength,high modulus and low thermal expansion coefficient etc.The microstructure,the microcrystalline structure,the skin-core structure and relative hardness of three kinds of high strength carbon fibers and three kinds of high modulus graphite fibers were studied by using scanning electron microscopy(SEM),Raman spectroscopy,X-ray diffraction(XRD)and transmission electron microscope(TEM).A new sample preparation method was proposed to detect the sections of carbon fiber by Raman Scattering Spectrum and transmission electron microscope,and the radial,axial and equatorial homogenization degree of Toray T800 S and two domestic T800 grade carbon fibers were analyzed by Raman spectroscopy,at the same time,the skin-core structure of the three kinds of carbon fibers were analyzed by TEM,in order to provide a theoretical reference for the production of high performance carbon fiber in China.The SEM results showed that the surface of Toray T800 S was smooth,and there was a groove with good orientation along the axial direction on the surface of two kinds of domestic T800-class carbon fiber.The fracture morphology of three kinds of carbon fibers was nearly round,and the roundness of the cross section of Dongli was the highest..The grooves on the surface of three high-modulus series of graphite fiber were deeper and denser than the high-strength series of carbon fiber,and the roundness of cross-sectionis was lower than the high-strength series.The surface smoothness and roundness of order from large to small was P311F>CCM46J>CCM40J,indicated that the surface of P311 F graphite fiber is the most dense,and the graphitization temperature is highest.The results of Raman and TEM indicated that three T800-class carbon fibers all have skin-core structures,the core diameter of JHT55 was about 1.60 ~ 1.78μm,but the 1.13 ~ 1.60μm of T800 S and P278 F.In addition,the homogeneities in the equatorial direction of three high-strength carbon fiber was also diffreent,but The Toray T800 S carbon fiber has the highest homogeneity.The graphitization degree of the three kinds of high modulus graphite fibers is very hig,and the lattice fringe arrangement regularity was increased from CCM40 J to P311 F,It can be proved that the structure of P311 F graphite fiber is close to the ideal graphite,whin lead to a higher tensile moduls.Toray T800 S has the largest crystallite size and the lowest internal porosity among the high-strength carbon fibers,which was an important reason to maintain high strength while maintaining a high modulus.The interplanar spacing002 d of P311 F graphite fiber is the smallest among the three high modulus series graphite fibers,the porosity of the three is decreasing from CCM40 J,CCM46J to P311 F.The hardness of carbon fiber in high strength series and high modulus series is as follows:T800S> P278F> JHT55,P311F> CCM46J> CCM40 J,which is consistent with the tensile modulus size,and indicated that the Modulus of carbon fiber can be reflected by the relative hardness by AFM.The mechanical properties of carbon fiber were determined by its all microstructure characterization,the smoother surface,less diameter,and improving the homogenization,retaining some amorphous structure contributed to the improvement of the strength of carbon fiber;increasing the crystallite size,the degree of orientationalong the fiber axis,reducing of the porosity,is conducive to improving the modulus of the graphite fiber.