Study On Carbon Fiber Composites Toughened By Interlayer Of Nano-particles Loaded With Polypropylene Nonwovens

In order to solve the"interlaminar failure"phenomenon of carbon fiber/epoxy resin（CF/EP）composites,improve its interlaminar fracture toughness,and enhance the comprehensive properties,the interlaminar toughening method was used to toughen CF/EP composites.Firstly,needle-like magnetic hydroxyl iron oxide（FeOOH）nanoparticles were prepared by liquid deposition-air oxidation,and the surface of FeOOH was chemically modified byγ-（methacryloxy）propyl trimethoxysilane（KH570）.The changes of surface functional groups,surface morphology,magnetic properties and atomic binding energy of nanoparticles were analyzed by means of fourier transform infrared spectroscopy（FTIR）,scanning electron microscope（SEM）,Vibrating sample magnetometer（VSM）,X-ray photoelectron spectrometer（XPS）and so on.Then,using polypropylene non-woven（PPNWF）as interlaminar base film material,conductive carbon black（CB）and FeOOH as loaded nanoparticles,PPNWF interlayer film materials loaded with different nanoparticles were prepared by infiltration method.The effects of FeOOH loading（2.9 g/m²,9.6 g/m²,16.5 g/m²,21 g/m²,30.5 g/m²）,modifier and magnetic field,and different ratios of CB and CB dispersant polyvinylpyrrolidone（PVP）（1:1,3:2,3:1）on the surface morphology of@PPNWF interlayer films were analyzed.Finally,using CF as the reinforced fiber material and EP as the polymer matrix material,the nano-particle@PPNWF/CF/EP composite laminate was successfully prepared by manual coating.The effects of different FeOOH@PPNWF interlayer films on the interlaminar fracture toughness of CF/EP composite laminate were studied.The effects of post-treatment temperature（80℃,150℃and 180℃）and pressure（0 MPa,3 MPa and 5 MPa）on the interlaminar fracture toughness and electrical conductivity of CB@PPNWF/CF/EP composite laminates were investigated systematically.At the same time,the fracture morphology of the composite laminate was studied by means of SEM,and the related toughening mechanism was studied.The main concluded are as follow:（1）Preparation and research of FeOOH@PPNWF/CF/EP composite laminate.Needle-like magnetic FeOOH nanoparticles with a length of 350-600 nm and a diameter of60-80 nm were successfully prepared by liquid phase deposition-air oxidation method.Moreover,with the increase of FeOOH loading,the interlaminar fracture toughness of Mode I and Mode II of CF/EP composite laminate increased at first and then decreased.When the load of FeOOH was 21 g/m²,the interlaminar performance of the composite laminate was the best.Compared with the uninterlay CF/EP composite laminate,the interlaminar toughness G_IC（1.06 k J/m²）and G_IIC（3.65 k J/m²）increased by 96%and 103%,respectively.This was attributed to the full infiltration of FeOOH nanoparticles in the EP matrix.At the same time,the interface roughness of EP was improved,and the shortcoming of brittleness of EP matrix was solved.And the pull-out,fracture,bridging and other behaviors of the FeOOH nanoparticles and the PPNWF fiber form a synergistic effect,which significantly enhanced the interlaminar fracture toughness of CF/EP.（2）Preparation and research of modified FeOOH@PPNWF/CF/EP composite laminate.After KH570 surface chemical modification of FeOOH,the interface interaction between FeOOH and EP matrix was enhanced,which induces more obvious plastic deformation and crack deflection of EP matrix.Under the action of the magnetic field,the needle-like FeOOH nanoparticles were arranged orderly between the EP matrix and CF and PPNWF fibers along the crack growth direction,which further promoted the deflection of the crack and improved the interlaminar fracture toughness.The mode I interlaminar toughness（1.48 k J/m²）of the FeOOH@PPNWF/CF/EP composite laminate modified by KH570 was significantly improved by 174%,and the mode II interlaminar toughness（3.83 k J/m²）was significantly increased by 113%.After magnetic field induction,the Mode I interlaminar toughness G_IC（1.62 k J/m²）of FeOOH@PPNWF/CF/EP composite laminate increased by 200%,and the Mode II interlaminar toughness G_IIC（3.76 k J/m²）increased by 109%.（3）Preparation and research of CB@PPNWF/CF/EP composite laminate.Because of the synergistic effect of CB particles and PPNWF,the toughening mechanism mainly included the enhancement of the toughness of EP matrix by CB,the debonding of the interface of CB particles,the enhancement of the interface of PP/EP by CB particles,the bridging,pulling out and breaking of PP fibers and so on.Moreover,the CB particles function as a bridge between the interlaminar of composite laminate,which significantly improves the problem of the decrease in the conductivity of the composite laminate layers due to the insulating material PPNWF interlayer film.The different temperature and pressure of post-treatment have different effects on the electrical conductivity and interlaminar fracture toughness of CF/EP composite laminate,and there are optimal conditions,so that the interlaminar toughness and electrical conductivity of CB@PPNWF/CF/EP composite plates are relatively better.Under the condition of post-treatment temperature of 80℃and pressure of 3 MPa,after the CB@PPNWF interlaminar modification,the interlaminar toughness G_IC（1.18 k J/m）of CF/EP composite laminate was increased by 115%,and the interlaminar volume The resistivity（52.54Ω·cm）decreased by 11.9%.