Interfacial Modification Of Carbon Fiber Reinforced Polyphenylene Sulfide And Its Composite Structure And Properties

Carbon fiber reinforced thermoplastic resin matrix composite（CFRTP）has the advantages of high strength,light weight,short processing cycle,good impact resistance and recyclability.Therefore,CFRTP gradually become one of the development directions of a new generation of carbon fiber composite materials.Among the common thermoplastic resins,polyphenylene sulfide（PPS）is one of the preferred resin matrixes for CFRTP due to its extremely low moisture absorption,outstanding thermal stability,good crystallinity and excellent solvent resistance.As early as the end of the last century,CF/PPS composite materials have been used in the tail wing of the Gulfstream G650 high-end business jet.In recent years,with the development of the aviation industry,CF/PPS composite materials have been widely used by Airbus,Boeing and other companies in secondary bearing structures such as aileron wing ribs,rudder leading edges and elevator auxiliary rib.However,due to the extremely high carbon content of carbon fiber and the large surface inertness,the infiltration effect of carbon fiber with PPS matrix is not good when preparing composite materials.Therefore,it is necessary to improve the wettability between CF and PPS through interface optimization to further improve CF/PPS.The interface bond strength and mechanical properties of composite materials.This thesis first systematically studied the effect of isothermal crystallization temperature on the structures and properties of CF/PPS composite materials.The mechanical properties of CF/PPS composite materials were improved by controlling the PPS crystal structure in the composites.Subsequently,KH570/PEK-C was used for surface treatment of the carbon fiber,and a thermoplastic resin transition layer was introduced at the interface of the composite material which further strengthened the interface bonding ability of the CF/PPS composite materials.Finally,on the basis of the above work,GO was introduced into the interface of the CF/PPS composite materials,and the interface performance of the CF/PPS composite materials was further improved through the combined action of chemical bonding,mechanical bonding and intermolecular entanglement.First,CF/PPS composite laminates were prepared by hot pressing using carbon fiber twill cloth and PPS film.The effect of PPS crystallinity and grain size on the mechanical properties of CF/PPS composite materials at different isothermal crystallization temperatures was systematically discussed.The results indicated that isothermal crystallization treatment can increase the crystallinity of PPS in the CF/PPS composite material while reducing its average grain size.When the isothermal crystallization temperature is 230 ℃,the average grain size of PPS in the CF/PPS composite material is reduced by 37.5% compared with the CF/PPS composite without isothermal crystallization treatment,and the crystallinity was increased by 12.07%.At this time,the CF/PPS composite materials has good interface bonding strength and rigidity.The interlaminar shear strength,flexural strength and flexural modulus reached 23.8 MPa,709 MPa and 81.9 GPa,respectively,which were increased by 47.8%,62.6% and 11.4% compared with the natural cooling composite material.When the isothermal crystallization temperature is too high,the PPS in the CF/PPS composite materials becomes hard and brittle due to the oxidative cross-linking reaction.At this time,the crystallinity of the PPS in the composite material is only 30.56%.And under this condition the mechanical properties of CF/PPS composite materials are poor.Subsequently,on the basis of isothermal crystallization treatment of CF/PPS composite materials,the influence of CF on the structure and properties of CF/PPS composite materials with PEI,PES and PEK-C three thermoplastic resin solutions（solvent: DMAC）was explored.XPS analysis shown that after surface treatment of CF with PEK-C solution,the number of oxygencontaining functional groups on the surface of CF can be greatly increased;At the same time,comparing the mechanical properties of the composites after treating CF with the three solutions of PEI,PES and PEK-C,it could be found that the interlaminar shear strength,flexural strength and flexural modulus of the composites after PEK-C solution treated CF are the best.When further investigating the effect of PEK-C solution concentration on the structure and properties of CF/PPS composite materials,it was found that with the increased of PEK-C solution concentration,the interlayer shear strength,flexural strength and flexural modulus of CF/PPS composite materials displayed the tendency to first increase and then decrease.And when the concentration of the PEKC solution is 0.5 wt%,the CF/PPS composite has the best interfacial and mechanical properties,at this time,the interlayer shear strength,flexural strength and flexural modulus are 38.45 MPa and839 MPa and 85.8 GPa,respectively.Finally,different concentrations of KH570 solution and 0.5 wt% PEK-C solution was employed to carry out the surface treatment of carbon fiber,and prepare the corresponding CF/PPS composite materials.The structures and properties of CF/PPS composite materials were studied after CF being treated by KH570/PEK-C.According to XPS analysis,after coating CF with 2 wt%KH570 solution and 0.5 wt% PEK-C solution,the O/C ratio and the bond content of C=O on the surface of CF increased by 137.5% and 122.6%,respectively compared with CF treated with 0.5wt%PEK-C solution,indicating that KH570 pre-treated carbon fiber can effectively improve the bonding ability of PEK-C and CF.At the same time,through the mechanical test,it is found that compared with the CF/PPS composite prepared by only using the PEK-C solution to treat the CF,the 2 wt%KH570 solution and the 0.5 wt% PEK-C solution were used simultaneously to deal with CF,the flexural strength and interlaminar shear strength of CF/PPS composite materials were increased by13.6% and 38.4%,respectively.On the basis of the above work,different concentrations of GO are introduced into the CF/PPS composite materials interface.The results demonstrated that when the GO concentration was 0.05 wt%,the interface bonding strength and mechanical properties of the CF/PPS composite were the best.The interlaminar shear strength and flexural strength were 56.2MPa and 1107 MPa,respectively,which were 5.4% and 16.2% higher than that of the composite without GO.