Study On Graphene Oxide Modified Carbon Fiber/Epoxy Resin Composites With Different Fiber Surface Properties

The large number of oxygen-containing functional groups contained on the surface of graphene oxide(GO)and its good compatibility with the resin matrix make it have great potential for modification of carbon fiber resin matrix composites.There are many varieties of carbon fiber(CF),but different CFs have different surface properties.In the process of GO modification of CF-reinforced epoxy resin(EP)matrix composites(CF/EP),the surface properties of CF will greatly affect the performance of composite materials.In this paper,the GO modified CF/EP composite is prepared by using three different CFs(domestic basic standard CCF300 carbon fiber,domestic high strength medium model CCF800 carbon fiber,domestic high strength high model CCM40J carbon fiber)as reinforcement Materials.Through the dynamic thermomechanical properties,interlayer shear properties,and micro-morphology of the composite materials,the modification effects of GO on the composite materials with different surface properties after normal and hygrothermal treatment treatment were studied.The effects of the surface properties of GO and CF on the composite material were studied through dynamic thermomechanical properties.The study showed that the addition of an appropriate amount of GO significantly increased the glass transition temperature(Tg)of the composite material,and the modification effect of 0.5%GO was the most significant.The Tg of 0.5%GO/CCF300/EP,0.5%GO/CCM40J/EP,0.5%GO/CCF800/EP composites is improved compared to unmodified CCF300/EP,CCM40J/EP,CCF800/EP composites,respectively 13.3?,10.5?,6?.Both the surface oxygen-carbon ratio and the surface groove of the carbon fiber will affect the Tg of the composite material.Among them,GO improved the Tg of the CCF300 composite with the highest surface oxygen-carbon ratio,followed by the CCM40J composite with deeper and denser surface grooves.GO/CF/EP after hygrothermal treatment,the Tg retention rate of GO/CF/EP is slightly lower than that of CF/EP.But GO/CF/EP after hygrothermal treatment,GO still has a certain improvement effect on the heat resistance of the three composite materials.Among them,GO/CCF300/EP composites with higher oxygen-carbon ratio have the greatest improvement.The influence of the surface properties of GO and CF on the composite material was studied by using the interlayer shear properties.The research shows that with the increase of GO content,the interlayer shear strength of GO/CF/EP increases first and then decreases.When the amount of GO added is 0.1%,the interlayer shear strength of the three types of GO/CF/EP reaches the maximum.The interlayer shear strength of 0.1%GO/CCF300/EP is 20.9%higher than that of CCF300/EP.The interlayer shear strength of 0.1%GO/CCM40J/EP is 10.7%higher than that of CCM40J/EP.The interlayer shear strength of 0.1%GO/CCM40J/EP is 15.3%higher than CCF800/EP.Among them,GO improved the CCF300 composite material with the highest surface oxygen-carbon ratio.GO/CF/EP after hygrothermal treatment,GO also improves the interlayer shear properties of the three CF/EP composites.Among them,CCF800 composites containing more surface treatment agents have the greatest improvement.However,GO keeps the retention rate of interlayer shear strength of the three types of GO/CF/EP after hygrothermal treatment to be lower than that of the corresponding CF/EP composite materials.The modification mechanism of the composite material was analyzed using micro-morphology.The results show that under normal conditions,the CF surface is smooth after the CF/EP is destroyed,and there are obvious peeling marks at the interface between EP and CF.After adding GO to modify,the CF surface in GO/CF/EP is obviously adhered to the resin,and the adhesion between the resin and CF is also tighter.The addition of GO improves the interaction between GO-EP-CF,improves the ability of GO/CF/EP composites to resist crack propagation,and effectively improves the interface properties of composites.After GO/CF/EP is subjected to hygrothermal treatment,water and heat cause the interface between the resin matrix and the fiber/matrix to be destroyed,thereby reducing the mechanical properties of CF/EP.In addition,the hydrophilic groups of GO also increase the erosion effect of water on GO/CF/EP,thereby exacerbating the decrease in the mechanical properties of GO/CF/EP.