Multi-scale Component Construction Of Carbon Fiber Surface And Study Of Its Composite Interface Performance

Carbon fiber(CF)has been applied widely in different domain due to its high-stiffness,high-strength,light-weight and excellent thermal and electrical conductivity.However,there are several problems with CF reinforced composites: weak interphase between fibers and the matrix,inefficiency and injured fibers.In this dissertation,our objective was to meet two requirements of different projects: a,the tensile strength(TS)of CF was greatly improved while the interface shear strength(IFSS)of the composites was improved,electro-chemical and electrophoretic deposition(EPD)were adopt to modify CF by introducing silver nanoparticles(Ag NPs)and graphene oxide(GO);b,IFSS of the composites was greatly improved without damaging fiber body,chemical grafting was adopt to modify CF by introducing polyether amine(D400)and GO.Morphology-controllable Ag NPs were deposited on CF surface via a facile and green EPD method in the presence of PVP for the fisrst time.It was found that the presence of PVP and its molar ratio(in terms of repeating unit)relative to silver nitrate both played important roles in determining the geometric shape and size of the Ag NPs(dendritic silver and particulate silver).The results suggested that time and concentration had a great effect on the content of silver,size of Ag NPs and surface roughness.TS and IFSS of Ag-loaded CF was improved by 29.2% and 57.2%,respectively.Electrical conductivity was two times higher than untreated CF.A layer of GO was deposited on continuous CFs by electrophoretic deposition(EPD)in isopropyl alcohol under ultrasonic treatment for the first time.After heat-treatment,TS of CF and IFSS of CF/epoxy composites were enhanced by 27.3% and 69.9%,respectively.CF which coverd by GO was partly reduced during the heat-treatment,and ionic bonds between CF and GO sheets became covalent bonds.CF/Ag NPs/graphene oxide(CF/Ag/GO)was prepared by electrochemical deposition and EPD.These Ag NPs and GO sheets worked very well in a ferocious synergy on the surfaces of CF.TS and IFSS of composites were enhanced by 31.3% and 86.1%,respectively.D400 was chemically grafted onto CF surface to prepare CF/D400 in water.We proved the presence of D400 with amino group could improve the surface energy and wettability of CF,and react with epoxy,which were responsible for the enhancement of IFSS of the ACF/D400 composites by 72.6%.The improvement of IFSS could be controlled by adjusting the concentration of D400.CF/D400/GO was prepared by chemical grafting,D400 as media.First,the influnce of surface morphology of GO grafted CF was realized via the sizes of GO.There were two types of CF and graphene connection:(1)the edges of GO connected with the CF surface,like “upright”;(2)the faces of GO connected with the CF surface,like “lying”.The “upright-liked” GO sheets were standing on the debonding fiber surface,which ensured that the mechanical interlocking and wettability between porcket-liked GO covered CF and matrix becomes much stronger.This could be good for transferring load and suppressing crack propagation in epoxy matrix.And the interfacial failure might transfer from adhesive mode to dominant cohesive mode which occurred in matrix.IFSS was improved by 82.1% to untreated CF.