Effect Of Modified Polyetheretherketon Sizing Agentt On Micro-Interfacial Proerties Of Carbon Fiber Composite Materials

With the development of science and technology,industrial production has placed higher demands on various properties of materials.Carbon fiber reinforced polyetheretherketone resin(CF/PEEK)composites have a wide range of applications in aerospace,military,automotive industry and energy equipment because of their excellent mechanical properties and thermal stability.The interface between CF and PEEK largely affects the mechanical properties of CF/PEEK composites,which serve as a bridge and link for stress transfer,and good interfacial properties are critical.The sizing agent can form a protective layer on the CF surface to avoid the production of hairy filaments in the CF process.The sizing agent treatment is more widely used due to the advantages of simple treatment process,flexible method,and easy industrial production,while a suitable sizing agent will enhance the wettability with the resin matrix while protecting CF.no cross-linkable chemically active functional groups are observed in the molecular structure of PEEK,and no chemical reactions occur during curing.The introduction of reactive functional groups on the PEEK backbone and their use as sizing agents for CF/PEEK composites can greatly improve the interfacial compatibility between CF and the PEEK matrix.In this thesis,a series of sizing agents based on the modification of polyetheretherketone itself were developed with the aim of bringing their properties into full play.First,this thesis designs and synthesizes modified PEEK with three different side groups.three PEEK resins containing three different polar side groups,namely sulfonic acid group,nitro group and methyl group,were successfully prepared using electrophilic substitution and nucleophilic substitution.two types of modified PEEK,partially crystalline and amorphous,were obtained by controlling different reaction conditions.the structure and crystallinity of the products were characterized and analyzed using nuclear magnetic resonance spectroscopy(NMR),Fourier infrared spectroscopy(FT-IR)and differential scanning calorimetry(DSC).The thermogravimetric analysis(TGA)showed that the modified PEEK still has good thermal stability and meets the demand for high temperature resistance of sizing agents in industrial production.Next,solution sizing was achieved by dissolving crystalline modified PEEK(S,N,C-PEEK)into a solution of pentafluorophenol.Electron microscopy(SEM)was used to determine the optimal mass fraction of resin in the sizing agent.Water-soluble modified PEEK(SS-PEEK)was dissolved into a mixture of water and acetone,and acidified and unacidified multi-walled carbon nanotubes(MWCNTs)in equal proportion to the resin were added to construct a composite phase interface for further investigation of the effect of the mixed sizing agent on the interfacial properties.X-ray electron spectroscopy(XPS)was used to confirm the changes in the chemical composition of the fiber surface after sizing of both types of modified PEEK.Finally,the interfacial property evaluation device of the composite showed that the interfacial strength(IFSS)between CF and PEEK resin was enhanced to some extent using crystalline and water-soluble modified PEEK sizing.The observation of interfacial crystalline diffraction between CF and PEEK by polarized light microscopy(POM)showed that the crystalline properties of modified PEEK(S,N,C-PEEK)had a large effect on IFSS.The MWCNTs in the hybrid sizing agent played an enhancing role to increase the mechanical riveting interaction compared to the resin-based sizing agent.Aging experiments have shown that crystalline sizing agents possess excellent chemical stability,making this type of sizing agent more versatile in the use environment.