Surface Modification Of Carbon Fiber And Properties Of Carbon Fiber Reinforced Resin Composites

The surface inertia of carbon fiber?CF?leads to interface problems between CF and the resin,which is a major factor limiting the mechanical properties of composites.In this thesis,the CF surface was modified by three different methods:?1?the collaborative coating of graphene oxide?GO?and SiO2;?2?two-step sizing of carbon point?CD?and sizing agent;?3?the coating of sizing agents with different nanoparticles,and the influences of modified CF on mechanical properties and interface of resin matrix composites were also discussed.Method one:the small layer GO?sGO?prepared by the centrifugal method and the SiO₂ modified by the silane coupling agent KH550 were used to coat together the surface of CF.First,the surface of CF with electrochemical treatment?ECF?was coated by s GO and then coated by SiO2,forming the layered structure of SiO2-sGO on the CF surface.Compared with ECF/epoxy resin?EP?composites,the interlaminar shear strength?ILSS?of SiO2-CF/EP composites,sGO-CF/EP composites and SiO2-sGO-CF/EP composites increased by 19.5%,10.99%and 33.45%,respectively.And the tensile strength increased by 8.24%,6.78%and 14.24%,respectively.Compared with the separate coating of sGO and SiO2,the coating of SiO2-sGO can more optimize the interface between CF and resin.Method two:three different sizing method were used to compare the enhanced effect of CD and epoxy sizing agent on CF composite materials,including?1?the coating of epoxy sizing agent?SD?;?2?one-step sizing of the mixture of CD and epoxy sizing agent?CD/SD?;?3?two-step sizing of CD and epoxy sizing agent?CF-SD?,namely,the desized CF?DCF?was first coated with CD,and then sized by epoxy sizing agent?SD?.The analyses of SEM and AFM showed that the two-step sizing method has the best sizing effect.The synergistic effect of interface micromorphology and sizing agent improved the sizing ratio and wettability of CF.Compared with DCF/EP composites,the ILSS values of CF-SD/EP,CF-CD/SD/EP and CF-0.15CD-SD/EP increased by 19.18%,21.41%,38.49%,respectively.Method three:in order to compare the effect of nano-particles sizing agent on the surface modification of CF,the CF surface was sized by the same sizing agent with three kinds of nano-particles?SiO2,carbon nanotubes?CNTs?and GO?with various concentrations.The three kinds of nano-particles sizing agent increased the mechanical properties of CF/polypropylene?CF/PP?composites to different degrees,but showing the same trend in the growth degree,That is,with the increase of the concentration of nano-particles,the mechanical properties of CF/PP composites increased and then decreased.Compared with CF coated by sizing agent/PP?CF-S/PP?composites,the best tensile strength of CF-2Si O2/PP,CF-5CNTs/PP and CF-1GO/PP increased by 4.8%,12.1%and 4.4%,respectively.In the meantime,the best bending strength of CF-2SiO₂/PP,CF-5CNTs/PP and CF-1GO/PP were improved by 9.3%,6.7%and 11.0%,respectively.