Structural And Damping Properties Of 3-D Braided Carbon Fibers Reinforced Epoxy Composites

Carbon fiber reinforced epoxy resin matrix composites are widely used in aerospace,high-speed railway,military and construction,due to this kind light weight composites with high specific strength and modulus,excellent mechanical properties and chemical corrosion resistance.But with the development of mechanical systems towards high-speed and automation,carbon fiber reinforced composites are more susceptible to vibration in mechanical systems.The high frequency vibration reduces the stability and safety of the mechanical system,accelerates the fatigue damage of the carbon fiber reinforced composites and shortens the service period of the composites.Therefore,it is a hot research topic to improve the damping performance of carbon fiber reinforced composites and prepare the structure-damping composite.Modified carbon fiber reinforced epoxy resin matrix composites were prepared by the method of resin transfer molding（RTM）.The surface of carbon fibers were modified by the double coating of PVDF&PDA and the carbon nanotubes（CNTs）coated by PDA.The mechanical properties of bending,shear and impact test and damping properties of composites were studied.Based on the results of mechanical test and vibration test,the damping mechanism and interface strengthening mechanism of modified composite were studied.The results show that the modification of PVDF&PDA double coating is simple,and the viscoelastic layer of PVDF increases the damping factor of the composite by70.6%.In addition,the PDA coating improves the bonding strength between carbon fiber and matrix,and maintains the excellent mechanics of the composite material.The method of chemical vapor deposition（CVD）was used to synthesize CNTs on the surface of CF3D to effectively improve the dispersion of CNTs in the resin matrix and improve the damping property of the composites.The CNTs synthesized on the surface of CF_3D by CVD proves can effectively optimize the dispersion of CNTs in resin matrix,so the damping property of composites is improved.Using poly-dopamine to modify the surface of the CNTs to improve the surfacial chemical activity of CNTs and improve the dispersion of CNTs in epoxy resin matrix.After treated by CNT@PDA,the attenuation coefficient of CNT@PDA-CF_3D/EP has improved 160%,and the flexule strength only decreased 8.5%compared with CF3D/EP.The modified composites have high damping properties while maintaining higher mechanical properties.The aim of preparing high damping and high strength structure-damping composites was achieved by controlling the micro interface of the composites.In addition,the research results are of guiding significance to the development and performance improvement of new structure-damping composites.