Study On Modified Carbon Fibers/Epoxy Resin Composites Interfacial Properties

Carbon fiber reinforced polymers(CFRPs)are versatile engineering materials that are used to different engineering applications owing to their high specific modulus,easy processing molding,corrosion resistance and so on.CFRPs are mainly composed of resin matrix and carbon fibers(CFs),which can be made in the form of continuous or uncontinuous unidirectional CFs,fabric or stacked fabric layers with different fibre orientations to fit different strength standards.Interfacial bonding between resin matrix and CFs reinforcement plays an important role in the overall performance of CFRPs.However,limited by the smooth surface,low surface energy and chemical inertness of CF,the interfacial bonding strength of CFs and resin matrix is still unsatisfactory.Therefore,it is necessary to modify the surface of CFs to improve the interfacial bonding of the composites.In this paper,continuous coating was used to modify the CFs with silanized nanocrystalline cellulose(NCC)for enhancing interfacial adhesion of CF/epoxy composites.NCC was prepared from cellulose powder by acid hydrolysis method and was silanized with 3-Aminopropyltriethoxysilane.Different mass fractions of AMEO-NCC were dispersed in E51/toluene containing 1.0 wt% E51.Then it was coated on the surface of CFs and the surface morphology was observed by SEM.The surface wettability of CFs was observed by the contact angle measuring instrument.Then the composites was prepared by the modified CFs and epoxy resin,and the interfacial shear strength(IFSS),interlayer shear strength(ILSS)and flexural properties were tested.The results showed that the interfacial property is the best when the content of the coated silane NCC is 0.3 wt%.An effective improvement the interfacial strength of CFRPs was revealed via the citric acid polymerization on the surface of CFs.Firstly,the polycitric acid(PCA)was grafted onto the surface of CFs,and then p-Phenylenediamine was grafted to enhance the interfacial properties.FTIR and XPS were applied to study the surface structures and reaction mechanisms.The surface appearance of the CFs was detected by SEM.The results of IFSS and ILSS test indicate that the IFSS of PCA treated CFRP increased by 31.5% for bare CFs without treat and p-Phenylenediamine grafting PCA treated CFs increases by 79.3% and 36.1% compared with untreated CF and oxidized CFs.