Characterization On Structure Of China-made Carbon Fiber And Interfacial Structure And Propertie Of Its Composite

Carbon fiber, has wide applications in national defense, aeronautics, gymnas- tics and transportation for their high specific strength, high specific modulus, wear resistance, erosion, fatigue and other excellent performance. With the development in the last five years, China now can produce performance-steady CF, which corre- sponds to T300.The mechanical properties of carbon fiber are mainly affected by its microstructure. Microstructure parameters, such as the layer spacing d002, the thickness of microcrystal Lc, the average diameter of the microcrystal La, were characterized by X-ray diffraction (XRD) and Raman spectroscopy respectively. With the improving of the graphitization degree of carbon fiber, d002 was decreasing, Lc and La was increasing. Comparison to the available, d002 of two kinds of GCF which are CCF-300 and ST300A are bigger than T300, Lc and La are between T300 and T700.Interface phase is one of the basic elements of composites and its structure and properties play a very important role on properties of materials. TDE-85 epoxy resin (diglycidyl-4,5-epoxycyclonexan-1,2-dicarboxylate), which is a cycloaliphati-c glycidyl type of three-functional epoxy resin with advantages of low viscosity, good process performance, easy operation, no volatile flavor and light color transparency, is applied in many high-tech fieles. In this paper, interfacial structure and properties of continuous carbon fibers reinforced CF/TDE-85 are studied.Surface morphology, surface chemical composition and interfacial structure of CF/TDE-85 composites were characterized by Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS) respectively. Interfacial properties were measured by using the dynamic contact angle method and the microdebonding experiments. The results showed that: T700 and T1000 have more smooth surface. Numbers of grooves and indications which exist on the surface of CCF-300 and ST300A are between T300 and T800. The diameters of T800 and T1000 are less than the other four carbon fibers; the results indicated that sizing agent on carbon fibers has greatly improved the surface activity, but the new chemical structure is not strong. So the action with the fibers is weak chemical or physical interaction. And there were new functional groups which can not be completely removed in on the interface of fiber and polymer, which can induced strong physical and chemical interaction on the interface of CF/TDE-85 and formed a good bonding. The amount of surface oxygen groups is 45.11% on T300/TDE-85, which is higher than 42.55% on CCF-300/TDE-85 and 35.25% on ST300A/TDE-85; Increasing the amount of -COOH(-COOR), the surface energy of T series carbon fibers are raising. And increasing the amount of oxygen groups, the surface energy of CCF-300 and ST300A are raising; The main factor affecting the stress transfer between the matrix and fiber is the surface oxygen groups of carbon fiber. Surface grooves, mechanical engagement and the wettability between matrix and fiber play a very small role to the interface intensity.