Study On Interlaminar Toughness Of CF/EP Composites Reinforced By Intercalation Film Based On Needle FeOOH

High-performance carbon fiber epoxy(CF/EP)composite materials have always been a key research work in the polymer field.However,the brittleness of EP can cause cracks and delamination in composite materials,and the surface of CF often exhibits high chemical inertness,resulting in the transfer of undesirable interfacial stress from the matrix to the fibers,thereby reducing the overall performance of the composite material.Therefore,improving the interlaminar fracture toughness of carbon fiber composites has become a common concern.In this paper,acicular magnetic iron oxyhydroxide(FeOOH)nanoparticles were prepared as the precursor by the liquid deposition-air oxidation method,and the magnetic field-oriented FeOOH-enhanced CF/EP composite laminate was prepared,and FeOOH synergetic was prepared based on the electrospinning technology.Polyvinylidene fluoride(PVDF)nanofiber intercalated reinforced CF/EP composite laminate and FeOOH blended PVDF electrospun intercalated film reinforced CF/EP composite laminate.The tensile testing machine carried out the double cantilever beam test(DCB)and the end notch bending test(ENF)on the composite laminates,and studied the type I interlaminar fracture toughness(G_IC)and type II interlaminar fracture toughness of different composite laminates(G_IIC)with the help of Fourier infrared spectroscopy(FTIR),transmission electron microscope(TEM),scanning electron microscope(SEM),vibrating sample magnetometer(VSM),X-ray diffraction(XRD)and tensile testing machine,etc.The micro morphology,the micro morphology of the fracture surface of the electrospun fiber membrane,the composite laminate,the magnetic properties of the particles,the change of functional groups,the composition of the fiber membrane,the chemical structure,and the mechanical properties were studied.The main conclusions are as follows:(1)Magnetic field-oriented needle-like FeOOH reinforced carbon fiber/epoxy resin laminates Type I and Type II interlayer fracture toughness:FeOOH particles and magnetic field-oriented MF-FeOOH particles are used as interlayer toughening nanofillers.The way of impregnation is to load the nano-particle absolute ethanol dispersion on the surface of carbon fiber to prepare FeOOH/CF and MF-FeOOH/CF,which are used as the intercalation of CF/EP composite laminates.Different areal densities(1.6 g/m²,2.4 g/m²,3.6 g/m²)FeOOH/CF/EP and MF-FeOOH/CF/EP(2.4 g/m²)toughening effect.The results show that when the areal density is 2.4 g/m²,FeOOH/CF/EP has the best toughening effect.Compared with the control(CF/EP),G_IC is increased by 38%and GIIC is increased by 76%.At the same time,the magnetic field-oriented MF-FeOOH/CF The interlayer fracture toughness of/EP is also improved.G_ICis increased by 62%and G_IIC is increased by 106%compared with the control sample.This is mainly due to the regular arrangement of FeOOH after magnetic field orientation,and the FeOOH forest forms a large area of nails between the layers.The tie structure contributes to the improvement of interlaminar fracture toughness.(2)Research on the interlayer fracture toughness of carbon fiber composites enhanced by FeOOH nano-particles and electrospinning fiber membrane intercalation:the polyvinylidene fluoride(PVDF)fiber membrane was prepared by electrospinning,and the anhydrous ethanol dispersion of FeOOH was loaded onto the surface of the carbon fiber by spraying.Two kinds of FeOOH/CF with different areal densities(1g/m²,2g/m²)were prepared,and the uniform dispersion of FeOOH on CF surface was observed by SEM.FeOOH/CF and PVDF nanofiber membranes were intercalated with CF/EP to prepare FeOOH and PVDF/CF/EP composite laminates with two surface densities.The results show that the G_IC and G_IIC of PVDF-CF/EP are only increased by 70%and 44%,respectively,and2g/m² FeOOH&PVDF/CF/EP shows the best toughening effect.G_IC and G_IIC are increased by 118%and 97%respectively.This is mainly attributed to the fact that the addition of FeOOH improves the fracture toughness of the matrix and also enhances the interfacial interaction with PVDF,which in turn strengthens the toughening behavior of PVDF.(3)Research on the fracture toughness of FeOOH@PVDF blended nanofiber reinforced carbon fiber composites:Electrospinning technology was used to mix FeOOH and PVDF together to prepare FeOOH@PVDF hybrid fiber membranes with different concentrations(0.5 wt%,1 wt%,2 wt%),the rough changes of FeOOH on the surface of PVDF were studied by SEM and TEM and compared with PVDF nanofiber membrane.The FeOOH@PVDF blended nanofiber membrane was used as the interlayer of CF/EP to prepare FeOOH@PVDF/CF/EP composite laminates.Among them,1wt%FeOOH@PVDF/CF/EP has the best toughening effect,the toughening effect of G_ICincreased by 180%and G_IIC increased by 150%.This is mainly attributed to the rough surface of FeOOH@PVDF blended fiber.Compared with PVDF,the composite laminate shows more obvious peeling,bridging,pull-out,stress and strain in the fracture process of the composite laminate,so as to absorb more energy,and ultimately affecting the composite laminate.The delamination resistance of the laminate has a positive effect.