| Fiber reinforced polymer matrix composites have a lot of merits,such as high strength-to-weight ratio,good fatigue resistance,good shock-absorbing, good processing properties,good biocompatibility,et al.Glass fiber,carbon fiber,aramid fiber,ultra high molecular weight polyethylene fiber are always used as reinfocred material in composites. Because of high specific strength, high modulus, high temperature resistance, corrosion resistance and other excellent performances,the aramid fiber reinforced resin matrix composite materials have been widely used in aviation, aerospace, military, automotive, mechanical, electrical and electronic, petrochemical and other fields.But the amide group of aramid structure are separated by benzene ring,aramid fiber have high crystallinity,high molecular symmetry,poor activity of H atom of the amide group.So ILSS of aramid fiber/epoxy resin matrix composite is poor. The content of diamine is increased in aramid Ⅲ than Ⅱ.So aramid Ⅲ have low symmetry,high performance of composite,high bingding capacity between aramid and epoxy.The application of the aramid fiber is still limited to some degree for the structure.Different modified methods to aramid Ⅲ are studied systematically, such as phosphoric acid modified method,coupling agent KH550modified method,acetic anhydride modified method,aqua regia modified method and plasma modified method.The aramid fibers are investigated by SEM and ILSS before and after being modified.The results show that plasma modification method is the most significant method, Three influencing factor(plasma treatment time, plasma treatment atmosphere, plasma treatment power) are studied systematically on the basis of previous research foundation.Finally,the optimal technique condition(7min,O2atmosphere,200W) was obtained.According to the process conditions of aramid epoxy composites interlaminar shear strength can reach69MPa, The modified mothod is very effective.Influence of plasma treatment to surface properties of aramid fiber is studied systematically.The results show that the crystallinity decreased from58.27%to a minimum of36.78%, aramid fiber surface O/C ratio significantly, from untreated was increased from0.27to0.40after the plasma treatment.The data from curve fitting of C1s spectrum have promoted considerably than the previous data.-C-C-group of fiber surface are indecreased to a minimum value of51.4%, while the-C-O-,-C=O and O-C=O three group content are12.1%,5%,11%, when the plasma processing time is7min.The surface of aramid fiber have significantly etched traces and roughness, and surface free energy of aramid is increased from45.4mJ/m2to74.3mJ/m2.The wettability of fiber surface obviously enhanced by plasma modified method which is advantageous to enhance the binding properties of aramid fiber/epoxy resin. At last, the mechanism of plasma surface treatment is discussed.Content of C,O,N elements on the surface of aramid fiber are analysised by XPS to study the effect of plasma surface treatment mothod for the fiber by SEM to observe morphology of aramid fiber surface,by DCAA to measure the wetting angle of fiber surface.The results show that plasma modified method can improve fiber surface composition and introduce the containing oxygen groups,but there is still significant degradation effect.The aramid fiber should be used at the first time in order to ensure the plasma treatment effects, even if it can not be prepared at the first time, which can be stored no more than3days.Effects of plasma treatment (different plasma treated time,different plasma treated power,differernt plasma treated atmosphere) on aramid/epoxy interfacial are studied systematically, oxygen plasma treatment can improve aramid/epoxy composite interface bonding performance which is mainly based on synergism between the aramid fiber-epoxy resin matrix chemical bonding and the effect and mechanical chimeric role of synergy,The damaged form of aramid fiber/epoxy composite is mixed failure.Ageing resistance of aramid/epoxy composite is investigated systematically to verify stability of aramid/epoxy composite after plasma treated. Variation of composite are studied under the hot oxygen aging conditions or ultraviolet aging condition.The results show that ILSS of the composite is not reduced significantly under ultraviolet aging in the range of160hours, and ILSS of the composite is not reduced under differernt thermal oxygen aging temperature for30days too. The functional groups of composite had no obvious variation,which confirmed that the composite has ability of resistance to harsh environment, wide application range, excellent performance, stability and many other ad vantages.The composite modified after plasma is widely used in engineering application. Biometrics of composite is divined by Flynn-Wall-Ozawa method Based on TG data.without considering the other aging conditions and other influencing factors, The composite can be used41.273years. The data of composite has a strong guiding significance in the project ’s field. |
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