The Investigation On Atomic Oxygen Erosion Resistance At The Interphase Of Carbon Fiber/Epoxy Composites

Due to outstanding material properties, carbon fiber/epoxy composites have been used extensively in equipment designed for the outer atmospheric service. However, serious erosion can occur to carbon fiber/epoxy composites from the interaction with atomic oxygen (AO) in low earth orbit (160-800km in altitude). Therefore, this paper proposed two modified methods in an attempt to improve the interfacial properties between carbon fibers and an epoxy matrix, and then improve atomic oxygen erosion resistance for the interface of CF/EP composites. Carbon fiber grafted with polyhedral oligomeric silsesquioxane (CF-POSS) hybrid reinforcement and the inorganic protective coating SiO2.In order to study the interface of POSS modified CF/EP composites, we selected three kinds of POSS, respectively, POSS-AM0265with amine group, POSS-EP0418and POSS-EP0409with epoxy groups. Firstly, carbon fiber grafted with POSS was characterized by X-ray photoelectron spectroscopies (XPS) and scanning electron microscopy (SEM). The results showed that the POSS particles grafted on the fiber surface, and the POSS-EP0409was high, the Si element was7.99%. Secondly, from the interfacial shear strength (IFSS) test, the results showed that POSS improved the CF/EP composites interface adhesive performance, the IFSS of CF/EP composites modified with EP0409increased by16.44%. The interlaminar shear strength (ILSS) and atomic force Microscopy were carried out to investigate the atomic oxygen erosion resistance at the interphase of carbon fiber/epoxy composites. It was noticed that, after carbon fiber surfaces were grafted with EP0418, EP0409and AM0265, the ILSS increased by5.56%,11.57%and3.22%. The atomic oxygen erosion resistance were better than that of untreated carbon fiber/epoxy composites, especially, the composites modified by EP0409. And, the ILSS of the composites declined obviously with the extension of exposure to atomic oxygen treatment, the untreated CF/EP composites had a large drop, with a drop of14.92%within8hours. While ILSS of CF/EP composites grafted with AM0265, EP0418and EP0409decreased only9.47%,5.66%and3.35%within8hours. Exposure to atomic oxygen treatment was carried out on the modified CF, the AFM test of CF gave the same conclusion that POSS had led AO-irradiated samples to form a SiO2passivation layer, which protected the underlying polymer from further AO attack and improved the interfacial adhesion.In order to study the interface of the inorganic protective coating SiO2modified CF/EP composites, we selected three kinds of concentration of SiO2coating, respectively,0.1%,0.5%and1.0%. Firstly, CF modified with SiO2 coating was characterized by X-ray photoelectron spectroscopies (XPS) and scanning electron microscopy (SEM). The results showed that the SiO2particles adsorbed on the fiber surface, and the0.5%SiO2coating was good. Secondly, from the interfacial shear strength (IFSS) test and interlaminar shear strength (ILSS), the results showed that SiO2improved the CF/EP composites interface adhesive performance, the IFSS increased by9.71%and the ILSS increased by9.85%. And, the ILSS of the composites declined with the extension of exposure to atomic oxygen treatment, the untreated CF/EP composites had a large drop, with a drop of14.92%within8hours. While ILSS of CF/EP composites modified with SiO2coating decreased only6.42%within8hours. Exposure to atomic oxygen treatment was carried out on the modified CF, the AFM test of CF gave the same conclusion that inorganic nano-SiO2protected the underlying polymer from further AO attack and improved the interfacial adhesion.