Study On Atomic Oxygen Erosion Resistance For The Interface Of Modified Carbon Fiber/epoxy Composites

When spacecraft is traveling in low earth orbit (LEO), atomic oxygen (AO), which is the most predominant and active species, may severely influence the lifetime of the spacecraft. CF/EP composites have wide applications in spacecraft materials, but they are particularly vulnerable to AO. Therefore, this paper proposed a new method in order to improve AO erosion resistance for the interface of carbon fiber/epoxy (CF/EP) composites. According to the characteristics of carbon fiber and epoxy resin, we chose the two modified systems, Au/thiols and hydroxylated surface/organic silane.In order to study the interface of Au/thiols self-assembly modified CF/EP composites, we selected the two aryl thiols molecules, respectively, amino thiophenol (ATP) and hydroxy thiophenol (HTP). Firstly, gold-plated CF was characterized by Scanning electron microscope (SEM), Atomic force microscopy (AFM) and X-ray diffraction (XRD). The results showed that the gold coating was uniform, dense and high purity. Secondly, the self-assembly films were analyzed by X-ray photoelectron spectroscopy (XPS) and surface-enhanced Raman scattering spectroscopy (SERS). The results indicated that two aromatic thiols indeed chemisorbed onto the Au-plated CF surface. From the interfacial shear strength (IFSS) test, it is noticed that, IFSS after Au-plated decreased. While after Au/CF surface were assembled with HTP and ATP, both of IFSS increased. Furthermore, with the extension of atomic oxygen exposure time, the IFSS of unmodified CF/EP composite materials declined dramatically, with a decrease of12.49%within2hours. While IFSS of microcomposites modified with Au coating, HTP and ATP decreased only6.73%,3.70%and1.28%within8h. AFM test of CF after atomic oxygen exposure gave the same conclusion that the Au coating and the two aryl thiols self-assembly modification could effectively protect the interface from atomic oxygen erosion.To study the interface of organic silane modified CF/EP composites, we chose three kinds of molecules, respectively, methyltrimethoxysilane(MS), y-aminopropyltriethoxysilane(APS) and y-glycidoxypropyl trimethoxysilane (GPS). Firstly, the carbon fiber surface, which had been oxidized and reduced, was characterized by XPS and capillary method. The results showed that the CF surface obtained more-OH functional groups. Secondly, the modified CF was characterized by XPS, FTIR and AFM. The results indicated that the organic silane molecules indeed chemisorbed onto the CF surface. Compared with untreated CF, IFSS of treated CF improved, which sequence was GPS>APS>MS. From the change trend of IFSS after atomic oxygen exposure, IFSS of modified microcomposites decreased a little,6.73%,3.70%and1.28%within8h. This means that the resistance to atomic oxygen of the interface of CF/EP composites was improved. Similarly, CF of AFM test after AO exposure had such a conclusion.