Preparation,mechanical And Tribological Properties Of Carbon Fiber Fabric Reinforced PI-based Composites

Polyimide(PI)is widely used in aerospace,automotive,microelectronics and other fields of advanced polymer materials,due to its easily synthesis,superior comprehensive performance.However,mechanical and tribological properties of pure PI can not meet the high requirements of some high precision fields.Carbon fiber fabric(CF)reinforced polymer composites have been extensively applied in modern automobile,ocean,aviation and other fields because of their advantages of anti-corrosion and wear resistance,noise reduction,high specific strength and easy processing.However,there is a huge difference between modulus and structure,thermal expansion coefficient and thermal conductivity and other physical properties between the fibers and resin.These distinctions will give the interface into different stresses,cause the transfer of stress to be uneven.In addition,due to the lack of active groups on CF surface,the interfacial bonding property of composites between fibers and polymer matrix is poor,which affects the thermal and mechanical properties of composites.Therefore,how to effectively regulate the surface of CF to achieve functionalization and reliability,promote the transfer of stress between interface of polymer matrix and CF,and modulate the structure of interface.It is still a challenge to optimize the strength and tribological properties of CF/PI composites.In order to develop advanced lightweight composites with high strength,excellent wear resistance and high temperature resistance,this paper has done the following research:1)The continuity of CF was used to improve the dispersion and stress transfer of the enhanced phase in PI matrix,based on the high activity of dopamine,a layer of polydopamine(PDA)was covalently grafted on the surface of CF.PDA introduced abundant amino and hydroxyl functional groups into CF,which enhanced the surface activity of CF.Therefore,the interfacial compatibility of matrix and fibers was greatly improved,made it covalent crosslinked with matrix.The application of three-dimension carbon fiber fabric can evenly extend the stress to every position of the material,the increase of thermal diffusion capacity can promptly emit heat generated during the friction process.Finally,the thermal,mechanical and tribological properties of PDA-CF/PI composite had been also significantly improved.2)The active groups on CF surface increased after modification with PDA.In order to further improve the interfacial adhesion of CF/PI and enhance the crosslinking degree between CF and PI matrix,the surface roughness of CF was improved.?-FeOOH was grown on the surface of PDA-CF composite by co-precipitation method.?-FeOOH has a special structure of tetragonal system,thus increase the surface roughness and contact area,more PI resin embedded into the trenches and grooves,resulting in mechanical interlocking.The adhesion between the PI resin and CF was enhanced.The results showed that ?-FeOOH and PDA interacted on enhancement of carbon fibers,which improved the surface activity of ?-FeOOH.The FeOOH-PDA-CF/PI composite prepared from surface functionalized carbon fiber fabric and polyimide matrix exhibit excellent thermal,mechanical properties and wear resistance.3)Polyaniline(PA)was grown onto surface of CF in situ by low temperature polymerization,then polyaniline nanofibers(PAN)can be obtained by reducing the concentration of aniline in the reaction solution and prolonging the reaction time.PAN containing the same amount of amino functional groups as PA,so the surface chemical activity of CF can be improved by the growing of PAN.At the same time,the fiber structure is arranged vertically on the surface of CF,which increases the roughness of CF surface and enhances the compatibility between CF and PI matrix.PAN modification can not only increase the chemical bond of CF surface,but also change the surface structure and roughness of CF.Through the comparative study of PA-CF composite and PAN-CF composite,it showed that the increase of interfacial adhesion promotes the formation of the transfer film during friction.In the composite,PAN helped carbon fibers bear part of external force and act as co-carrier of force with CF in the composite.Therefore,the CF/PI composite present superior tensile performance after the addition of PAN.In addition,the friction coefficient and anti-wear performance wear resistance of the composites were both increased.