Preparation Of Carbon Fiber Modified With Carbon Nanomaterials Sizing Agents And Study On Mechanical Properties Of Composites

Due to their high specific modulus,high specific strength and light weight,carbon fiber rein polymer composites(CFRP)has been widely used in aerospace,automobile manufacturing and other fields.However,the carbon fiber(CF)surface is chemical inert,which result in poor interface interaction between the fiber and the resin matrix.The the overall performance and service life of composites were limited by week interface adhesion.Therefore,it is necessary to modify the carbon fiber surface.In this study,the carbon nanotubes,graphene and graphene/carbon nanotubes mixture sizing agents were respectively introduced onto the surface of carbon fiber by coating method to prepare carbon nanomaterials/carbon fiber multiscale reinforcement.The modified carbon fiber/epoxy composities were manufactured by the hot-pressing molding process.Morphology of the carbon fiber surface,mechanical properties and interfacial properties of composites were characterized.The effect of carbon nanomaterials on strengthening and toughening mechanism of modify carbon fiber/epoxy composites was investigated.The main research contents and results are as follows:(1)The sizing agents of carbon nanotubes,graphene and graphene-carbon nanotubes mixture were separately prepared by sonication method.The desizing CF was sereparetly dipped in different sizing agents.The CF modified by different mass fractions of E51 sizing agent was characterized by thermo-gravimetric(TG)and results showed that the E51 was successfully applied to the fiber surface and improved the interface bonding effect between MWCNTs and the CF surface.The results of field emission scanning electron microscopy(FE-SEM)showed that carbon nanotubes,graphene and graphene-carbon nanotubes mixtures were successfully applied to the CF surface.A thermo-gravimetric(TG)was used to measure the relative weight content of epoxy.It was found that the content of epoxy on carbon fiber surface were higher when the epoxy concentration was 1wt%-1.5wt%.(2)The mechanical properties and interface properties of composites were characterized by electro-mechanical universal testing machines and results indicated that the monofilament and multifilament tensile strength of CF modified with 0.5 wt% MWCNTs sizing agents increased by 17.2% and 70.8% respectively compared to the desizing CF,the monofilament and multifilament tensile strength of CF modified with 0.5wt% GnP sizing agents increased by 13.8% and 70.2% respectively compared to the desizing CF,the monofilament and multifilament tensile strength of modified with 0.5wt% GnP-MWCNTs sizing agents increased by 27.6% and 73.4% respectively compared to the desizing CF.Compared with the desizing CF/epoxy composite,the tensile strength and bending strength of MWCNTs sizing agents modified CF/epoxy composites increased by 51.9% and 42.8% respectively,the tensile strength and bending strength of GnP sizing agents modified CF/epoxy composites increased by 50.1% and 41.1% respectively;the tensile strength and bending strength of GnP-MWCNTs sizing agents modified CF/epoxy composites increased by 71.4% and 53.3% respectively.The interlaminar shear strength of MWCNTs sizing agents,GnP sizing agents,and GnP-MWCNTs sizing agents modifying CF/epoxy composites increased by 72.9%,71.3% and 89.6% respectively.The FE-SEM results of the fracture morphology of composites show that there are more fibers in the fracture of the desizing CF/epoxy composite and the surface of the extracted fibers is smooth.However,only a small amount of fibers were extracted from the fractures of MWCNTs sizing agents,GnP sizing agents and GnP-MWCNTs sizing agents modified CF/epoxy composites.The fiber surface was covered with a large amount of resin and the fibers were tightly bonded.It indicated that the interfacial interaction between the CF modified by MWCNTs sizing agents,GnP sizing agents,GnP-MWCNTs sizing agents and the resin was enhanced and the interface strength was improved.The reason why GnP-MWCNTs modified CF and composites have the highest performance was that GnP inhibits the agglomeration of MWCNTs and improved the uniformity of dispersion on the surface of carbon fibers.The three-dimensional structure of GnP and MWCNTs increased the roughness and specific surface area of the CF surface greatly and enhanced the mechanical anchoring between fiber and resin matrix,thus making the mechanical properties of CF and composites modified by GnP-MWCNTs more excellent.