Study On Sizing And The Effect On Properties Of Carbon Fiber

Carbon fiber and its composites have various good properties: high specificstrength, high specific modulus, high temperature resistance, corrosion resistance,fatigue resistance, low thermal expansion coefficient, and so on. So they offerversatile applications in many fields. However, carbon fibers are brittle materialsand are easy to occur fluffs and filament breakages in the manufacturing process.Meanwhile, the strength of carbon fibers will decrease. Therefore, sizing for carbonfibers are necessary. Sizing is one important assistant material in the industries ofcarbon fibers，which have many special applications in protecting and improving thefiber surface properties and so on．At present, domestic investigations in this area isbehind overseas ones，the main reasons are ascribed to great1ag in the industries ofcarbon fibers and blockage of foreign technologies．Therefore，it is indispensable forus through self-reliance to renovate high performance sizing．The research hasimportant significance for promoting the domestic general self-production of carbonfibers．This paper investigates the effect of the sizing agent types and concentration onthe microstructure and mechanical properties of carbon fiber in different precursorby single fiber fragment test, SEM and TG, based on the extensive survey for theoverseas and domestic develop of sizing．Meanwhile, the contribution of sizing oninterfacial bonding properties of composites is investigated.The relativemechanisms of sizing are introduced．The main conclusions are as follows：(1) As a comparison with unsized carbon fiber, after solvent type and emulsiontype sizing treatment，the surface morphology of mesophase pitch based carbon fiberCF511D and PAN carbon fiber occur larger changes, and the different concentrationsizing agents have diverse influences on the surface morphology. Sizing agentdistribute uniformly on the surface of the carbon fibers which are sized properly, andthe amount of sizing agent is appropriate.(2) As a comparison with unsized carbon fiber, after solvent type and emulsiontype sizing treatment，the surface roughness of mesophase pitch based carbon fiberCF511D and PAN carbon fiber are increase.(3) The strength of carbon fibers are increased by sizing treatment, indicatingthat sizing treatment can recover the number of surface defects, which improves the mechanical properties of carbon fibers.(4) According to the weibull plots of the strength of sized carbon fibers, weibullmodulus is increased by sizing treatment, demonstrating that scattering is decreasedby appropriate concentration sizing treatment. The scattering of strength can belessened by appropriate sizing treatment.(5)The different concentration sizing agents have diverse influences on theinterfacial shear strength of carbon fibers reinforced plastics. Not all sizing agentcan improve the interfacial property, and it is necessary to choose appropriate sizingagent. For mesophase pitch based carbon fiber CF511D, the appropriate sizing agentconcentration is about1%.