Preparation And Properties Of Carbon Fiber/electrospun Polyimide Composites

Carbon Fiber Reinforced Epoxy Composite(CF/EP)have excellent properties such as high strength and high modulus,so they are widely used in cutting-edge fields such as aerospace and aviation.However,due to the brittleness of the epoxy resin matrix,the structure made of advanced CF/EP has the potential risk of internal defect propagation under impact and fatigue loads.Therefore,in this paper,nano-scale thermoplastic Polyimide(PI)fiber membrane was used to toughen CF/EP composites.In this paper,based on electrospinning technology,CF/EP laminates toughened by PI nanofiber films with different surface densities were prepared,and the effects of PI nanofiber films on the interlaminar fracture toughness of type I and type II composites were studied.First,PI nanofiber membrane was prepared by electrostatic spinning technology.The influences of polymer solution concentration,spinning voltage,spinning speed,spinning distance and environmental humidity on fiber morphology and diameter were studied.The universal tensile testing machine,Thermogravimetry(TG),Differential scanning calorimetry(DSC)and water contact Angle test were used to test the mechanical properties,thermal stability and surface wetting properties of the fiber.Meanwhile,Fourier Transform Infrared Spectroscopy(FTIR)was used to characterize the structure of the fiber membrane.Using the autoclave process,PI nanofiber membrane was added between the CF/EP prepreg layers to prepare a composite material,and the interlaminar toughness of PI nanofiber membrane toughened CF/EP composite I at different surface densities was studied by Double Catilever Beam test(DCB).In the test,for the I-type interlaminar toughness,the load-open displacement curve was tested,and according to the Modified Beam Theory(MBT)Method,the interlaminar fracture toughness value and its average value(G_IC)were calculated after PI nanofiber membrane with different surface densities toughened the CF/EP composite material.The research shows that with the addition of PI nanofiber membrane,the peak load and G_IC of type I stratification are effectively enhanced.The unilateral notched 3-Poing End Notched Flexure test(3 ENF)was used to study the interlaminar toughness of CF/EP composites the type II toughened by PI nanofiber membranes with different areal densities.For the type II interlayer toughness test,the load-displacement curve was tested through the 3 ENF test.It was found that compared with the untoughened sample,the interlayer toughness value and the critical load of crack propagation after adding PI nanofiber membranes with different areal densities were slightly decreased.