A Novel Hybrid Coating Modified Aramid Fiber Composites And Its Interfacial Properties

Aramid fibers are high-performance fibers that have attracted commercial and academicinterest because of its excellent tensile strength, modulus, toughness, high temperature resistanceand impact resistance properties. Aramid fiber-reinforced polymer composites are widely used inaerospace, automotives, and industries because of their outstanding properties, such as highspecific strength, low density, and flexible design. However, it is known that aramid fibers havetwo troublesome problems. The first is poor surface activity. Aramid fiber-reinforced polymercomposites demonstrate poor interfacial adhesion because aramid fibers exhibit chemicalresistance to the active groups of the polymer matrix. The second shortcoming is poor UVresistance, the UV radiation could deteriorate the structure of aramid fibers and their mechanicalproperties.In order to overcome the two critical disadvantages of aramid fibers, novel hybrid coatingswere prepared and used to the surface modification of aramid fibers. This paper studied theeffect of hybrid coating treatment on the aramid fiber, especially the UV resistance performance.Further, with the modified aramid fiber as a reinforcing material for preparing compositematerials, study on the effect on improving the interface of aramid fiber composite materials.In this study, silicon/shape memory polyurethane (SiO2/SMPU) hybrid coatings wereprepared using a sol–gel process with moisture in the air as the source. The structural andmorphology of the SiO2/SMPU hybrid coatings were studied by scanning electron microscope(SEM), transmission electron microscope (TEM), etc. Results indicated that the hybrid coatingsexhibited size distribution from11.9nm to61.7nm and good dispersion. In addition, the hybridsols were characterized by transparency and excellent storability even after six months whenstored in an inert atmosphere. Thus, this capability has the potential to widen the industrialapplications of coatings.Then, aramid fibers were pretreated conventional methods and modified using synthesizedSiO2/SMPU hybrid coatings. The chemical structure, morphology, physical activity andapplication performance of aramid fiber by analysis and testing through the infrared spectroscopy (FTIR), X ray photoelectron spectroscopy (XPS), atomic force microscopy(AFM), scanning electron microscope (SEM), etc. The results showed, after hybrid coatingstreatment, UV resistance performance of aramid fiber is improved obviously.Further, this paper focuses on the mechanism discussion of the interfacial bonding andfracture morphology through the single fiber fragmentation test (SFFT) and scanning electronmicroscope observation method. According to the research on the modification of SiO2/SMPUhybrid coatings, results show that specific surface area and more polar groups are formed on thesurface of aramid fiber, which come from the "pizza-like structure coatings. Therefore, fiberand resin formed a more optimized interface through the mechanical binding and wettingadsorption, the mechanical properties of the composite can play better. Finally, interfacial shearstrength (IFSS) of the aramid fiber reinforced shape memory polyurethane resin compositesimproved by70%, aramid fiber reinforced epoxy resin composites improved by50%. Theresults showed, after hybrid coatings treatment, interfacial adhesion performance of aramidfiber-reinforced polymer composites is improved obviously.