Study On The Effect Of "Stone-and-cement" Nanostructured APEI-GO Interphase On The Interfacial Performance At Elevated Temperature And The Hydrothermal Behavior Of Carbon Fiber Composite

With the development of carbon fiber composites,the demand for heat-resistance carbon fiber reinforced composite materials is increasing rapidly,and the performance of carbon fiber composites at high temperature has become another goal after the pursult of light-weight requirements.At present,the overall properties of the composites are largely limited by the poor interfacial adhesion of the composite.Therefore,the research key and hotspot of high temperature resistant composites is to establish a scientific method to improve the interface performance at elevated temperature.Based on the design concept of synergistic enhancement via "mechanical bonding and chemical bonding",graphene oxide(GO)and amino polyetherimide(APEI)were introduced on the surface of desized carbon fiber by electrophoretic deposition and dip-coating,the "cement-and-sand"-like APEI-GO multiscale interface was constructed successfully.The effect of the APEI-GO multi-scale interface on the interfacial performance and moisture resistance of the T800 carbon fiber/epoxy matrix composite was systematically studied at room temperature and high temperature,and the theoretical basis and basic data for the study of improving the interfacial performance at high temperature and moisture resistance are provided.Based on the grafting method,triethylenetetramine aminated modified polyetherimide(APEI)was prepared,and then the anodizing,EPD and dip-coating methods were successfully used to construct the"cement-and-sand"-like APEI-GO multiscale interface.The structure of the modified product(APEI)was characterized by means of FT-IR and TGA.The results of SEM,AFM,XPS,and contact angle test showed that the activated carbon fibers could deposit GO more efficiently,and the surface roughness and the chemical activity of carbon fibers were significantly increased by the introduction of APEI-GO multi-scale interface.The effect of APEI-GO multi-scale interface on the interfacial properties at high temperature of composites was systematically studied.The interfacial strength at different temperatures was characterized by means of the transverse fiber bundle tensile test(TFBT)and fiber bundle pull-out test(FBPT).The transverse fiber bundle tensile(TFBT)and fiber bundle pull-out(FBPT)of APEI-GO@CF/EP composite was 54.3%and 115.6%higher than CF-commercial/EP composites at 180?,respectively.Acoustic emission(AE)technology was used to study the destruction process of the composite.The glass transition temperature and interface activation energy of the interface phase were characterized by differential scanning calorimeter(DSC)and dynamic thermal mechanical performance analyzer(DMTA).The micromechanical model of the interface was characterized by the mechanical model of atomic force microscope(f-AFM).The test results showed that the Tg and activation energy of the composite interface were effectively increased by the APEI-GO multi-scale interface,and the thickness of the interface modulus transition layer was also increased.Thus,the interfacial performance at high temperature was remarkably improved.In addition,based on the study of the interface properties at high temperature,the moisture resistance of the interface was analyzed.When reached the saturated moisture absorption,the interlaminar shear strength retention rate of APEI-GO@CF/EP composite could reach 91.7%.The cross-link density of the interface phase was effectively increased by the APEI-GO multi-scale interface structure,thereby the diffusion of water vapor was prevented and the moisture resistance of the interface was improved.