Prepatation Of Polymer Microsphere-Carbon Fiber Reinforcement And Study Of Composite Interface Proformance

Carbon fiber reinforced polymer matrix composites(CFRPC)are widely applied in civilian,military and other fields due to their excellent performance characteristics.However,the fiber surface show chemical inertness and the functional activity is lowered,resulting in poor interfacial compatibility with the resin matrix,thereby affecting the overall performance and service life of the composites.Therefore,it is necessary to modify the fiber surface.The surface modification methods for carbon fiber mainly includes physical and chemical modification methods,and the modification mainly involves changing surface composition and surface roughness of the fiber.Introducing micro-nano structural materials into the fiber surface can simultaneously improve fiber surface roughness and surface functional activity.It has been reported that the surface modification for carbon fiber is carried out by electrophoretic deposition.Positively-charged polymer microsphere is electrophoretically adsorbed onto the fiber surface.The method is simple and rapid.But the composition,structure and morphology of the microspheres are single,and only is PMMA microspheres with spherical,smooth surface which is compatible with PMMA resin substrate.and the surface lacks functional groups.In-situ growth of polyphosphazene hybrid microspheres orito the acidified fiber surface by chemical grafting,but strong acid treatment damages fiber body.And the chemical reaction step is complicated,time-consuming.the conditions are harsh.For this purpose,it puts forward the idea of the thesis:electrophoresis and chemical grafting methods are used to modify the fiber surface by introducing polymer microspheres with controllable adjustment of composition,structure,size and morphology into the fiber surface,which can greatly increase the surface roughness and surface energy of the fiber,improve interfacial adhesion and enhance mechanical interlocking of composites.Thus obtain the high performance resin-based composites.The main work of the thesis is described as follows:1.Electrophoretic deposition of polymer microspheres on carbon fiber surface-improving interfacial properties of composites:(1)P(St-GMA)particles were prepared by one-pot dispersion polymerization two-step method.Different sizes particles with surface morphology spherical,core-shell,surface roughness and raspberry-like are produced by varying the second comonomer content and dispersion medium.The surface amine and thiol functionalized P(St-GMA)particles are prepared by chemical reaction;(2)The effects of voltage,time and functional microsphere type on the particles loading rate on fiber surface are studied.And electrophoresis parameters are determined to be 15v(voltage)and 90s(time).The changes of surface composition,wettability and interfacial properties of composites after electrophoretic deposition modification are investigated.The electrophoresis voltage is 15v,time is 90s,and the particles are P(St-35%GMA)-NH2-270nm with rough surface,the fiber surface particles is distributed uniformly,the particle loading rate is 14.9%,and the surface energy is maximum for 49.18 mN/m,increases by 97.43%,compared to the untreated fiber.The mechanical strengths(TFBT and IFSS)of the composites are 30.15 MPa and 51.13 MPa,which are 88.08%and 30.77%higher than those of the unmodified fiber composites.2.In-situ growth of click particles onto carbon fiber surface-improving interfacial properties of composites:(1)PDA coating is deposited on the fiber surface at room temperature,and the fiber surface is subjected to-NCO functionalization by surface amine group react with isocyanate group.Then in-situ click polymerization on the fiber surface to grow polymer particles.The effects of monomer feeding mode,click monomer types,feeding amount and ratio on the morphology,structural and properties of fiber surface are investigated.A methods of in-situ modification of fiber surface by thiol-isocyanate click-dispersion polymerization with PETMP and IPDI as click monomer is established by IPDI feed amount of 5mmol-NCO for first-stage.The Weibull parameter analysis method is used to evaluate the bulk strength before and after chemical modification.It is found that the strength of monofilament fiber modified by PDA and Click NPs(monomers of PETMP and IPDI)increases by 9.68%;(2)The effects of monomer feeding amount on the interfacial properties of composites is investigated.As the monomer feeding amount increases,the fiber surface energy and composite mechanical properties(TFBT and IFSS)increase first and then reduce,when the PETMP and IPDI monomer feeding ratio are[n(-SH):n(-NCO)=9:9mmol],the fiber have the highest surface energy and mechanical strength.When the fiber surface is further grafted with the curing agent TETA,the surface energy is further increased,and its value is 50.67 mN/m,which is 144.48%higher than that of unmodified CF.And interfacial strength(TFBT and IFSS)of composites increase by 150.97%and 76.42%,respectively;(3)According to the SEM image of TFBT mechanical failure and the fluorescence spectra of before and after IFSS mechanical debonding,the interface enhancement mechanism of composites is proposed:PDA coating and click particles as a polymer interphase-protective layer,when the composite is under load,it can reduce stress concentration,dissipate extra energy,change the crack transmission path,prevent the crack from directly extending to the fiber surface,and let the stress be evenly distributed and dispersed,thus enhancing the interface chemistry and physical mechanical interlocking effect.