Study On The Preparation And Properties Of Carbon Fibers Surface Modification Reinforced Epoxy Resin Composites

Carbon fiber reinforced polymer composites?CFRPs?with excellent physicochemical performance including high specific strength,stiffness,low weight,corrosion resistance,great thermal stability and easy modeling,which have been widely used in aerospace,defense,transportation,wind power generation and sport utilities.Indeed,the interface between fibers and matrix is an important factor to enhance the overall mechanical properties of composites.However,the carbon fibers surface are smooth,chemical inertness and low surface energy,causing weak interfacial adhesion between fibers and matrix.Therefore,the surface of carbon fibers need to modification.In recently,many methods for surface modification of fibers have been developed to enhance the interfacial properties of composites through increasing the polarity,surface roughness and surface energy.Unfortunately,most of these methods involves the sacrificing of intrinsic strength of fiber,long time,toxic polar organic reagents,etc.In this paper,from the perspective of the structural characteristics of carbon fiber and epoxy resin and the interface microstructure of the composites,without sacrificing the intrinsic strength of single fiber and reducing environmental pollution.With the outstanding performance of silica?SiO₂?,graphene oxide?GO?and polyetheramine?PEA?were introduced the surface of CF by physical or chemical interaction.These modification methods improved the wettability,mechanical interlocking and chemical bonding between fibers and resin matrix,and then enhancing the interfacial or mechanical properties of carbon fiber/epoxy resin composites.The negative charged GO and positive charged SiO₂?amino functionalized,SiO₂-NH₂?were deposited onto CF surface via a facile,green and effective Layer-by-Layer?LbL?self assembly method on which polyelectrolytes-PEI was utilized as the“bridge”based on electrostatic interactions.The effects of different layers of GO/SiO₂ multilayers films on surface microstructure,chemical composition and intrinsic properties of carbon fiber and interfacial or mechanical performance of its composites were investigated systematically.The introduction of GO/SiO₂ multilayers films greatly improved the fiber roughness,surface energy and chemical groups,and the scanning electron microscopy?SEM?revealed the GO/SiO₂ multilayers films were compact and homogeneous coverage onto CF surfaces.Compared to that of Untreated-CF composites,the interfacial shear strength?IFSS?,interlaminar shear strength?ILSS?and flexural strength of CF composites with assembly 5layers were increased by 86.1%,89.3%and 30.4%,respectively.Moreover,the dynamic mechanical properties?DMA?and energy dispersive spectroscopy?EDS?mapping of CF composites also show a great interfacial adhesion.Meanwhile,the tensile strength?TS?of single fiber increased from 3.52 GPa to 3.68 GPa after LbL self assembly of GO/SiO₂.On the other hand,the PEA with different varying molecular chain lengths were coated onto CF surface by chemically grafting method in mild aqueous solution.Atomic force microscope?AFM?shows the introduction of PEA could improve the surface roughness,polarity and wettability of CF,and the amino group at one end of PEA react with epoxy resin,which enhancing the interfacial adhesion between fibers and resin matrix.Compared to that of Untreated-CF composites,the IFSS and ILSS of CF-D400 composites were increased by 91.2%and 46.6%,respectively.In addition,the flexural strength also has shown an increase of 37.1%.Meanwhile,the modification procedure did not bring deterioration the TS of single fiber.