| Ultrahigh molecular weight polyethylene(UHMWPE) fiber, which is a linear chain structure of high crystallization and high orientation, is the third generation of high-performance fibers appearing following carbon fibers, Kevlar fibers. It can have a prospect used extensively in the fields of national defense , aviation and navigation, sports and medical treatment etc because of very low density, high-strength, high modulus, excellent energy absorbance, good impact resistance, good corrosion-resistance and so on.However, UHMWPE fibers and its composites have not been extensively applied in reality, because UHMWPE fibers are composed of methylene with linear long chain and non-polarity, don't have heavy polar group, fibers' surface has no active point, and ultrahigh drawn fibers' surface is quite smooth, so it is difficult for both fibers and resin to form chemical bond, fiber-matrix interfacial adhesive strength is low, mechanicals performances of the fiber composite are influenced; In addition, the high crystallization and high orientation have aggravated the anisotropic property of the fiber further, it makes that the crosswise strength of the fiber composite is low. Thus, it is limited as the application of the structural material.The common methods of surface modification on UHMWPE fiber is physical , chemical , physical-chemical method for improvement of the adhesive properties between fiber and matrix, such as low pressure plasma treatment, chemical reagent oxidation, surface grafting, calendering method , coating method and so on. In these methods, it is necessary to pump out the air close to the vacuum in production and treated fibers will be provided prescroption although the low pressure plasma treatment is small to environmental impact and the result is obvious, so it is difficult for this method to modify on UHMWPE fiber in industrialization. And atmospheric plasma treatment can solve this problem effectively.The optimization of surface modification about UHMWPE fiber was researched in order to investigate the integrative influences of two factors on mechanical properties and bonding property of treated fiber by the atmospheric plasma method of dielectric barrier discharge, with a central compound rotation of design under five levels, and longitudinal surface condition was observed by scanning electron microscope in the paper. The optimum technical parameters are as follow: treatment time, 4.667 minutes; treatment volt , 7375.677V, these optimum technical parameters was proved by experiment.In order to verify the improvement of bonding property of treated fiber by the optimum technical parameters, fiber reinforced composites were made by fibers and treated fibers separately, mechanic performances, which is longitudinal-wise , crosswise, hypoid-wise, and tested results were tested separately and compared between untreated and treated fiber reinforced composites.Through a series of experiments and analysis, following conclusions were got:1 , The fiber assemblies' strength had been damaged after plasma treatment, but the degree of damage was not high. It was observed that the vertical surface of treated fiber had formed the shallow holes of carving from photo of scanning electron microscope. This is main reason that bonding property of fiber could be improved.2, The bonding property between treated fiber by plasma and epoxy resin has greater improvement.3, The mechanics performances of longitudinal-wise, crosswise and hypoid-wise of composite, which is made of treated fiber and low density polyethylene film, have greater improvement. It is proved that treated fiber has got the result of modifying desirably.The modifying method on UHMWPE fiber with atmospheric argon plasma of dielectric barrier discharge can make bonding property of fiber get greater improvement, then, UNMWPE fiber will obtain heavy use in reality in the field of composites.
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