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In this study, the hyperbranched polyester (HBP) was grafted onto the surface of graphene oxide (GO) to prepare functionalised GO (fGO). Results of X-ray photoelectron spectra, Thermogravimetric analysis, Fourier transform infrared spectroscopy and Transmission Electron Microscopy confirmed the success of grafting. Moreover, the anti-corrosion performance and barrier properties of the bare steel, and steel with epoxy (EP) coating, steel coated with EP/GO and EP/fGO were comparatively studied. It was found that EP/fGO showed enhanced anti-corrosion capability and barrier properties to H 2 O and O 2 compared with EP/GO, attributed to the surface modification of GO by HBP. Moreover, the role of surface modification using HBP on the performance of EP/GO composite coating was also discussed, related mechanism was proposed.

Abstract:Due to the problems of potential corrosion and thermal expansion differences between traditional metal connecting pieces and carbon fiber poles, it is difficult for them to meet the operating requirements of truss structures in the environment of stratosphere. Based on the large scale composite space truss structure of stratosphere aerostats, the carbon fiber flange connection joints were studied in the present paper. Adopting the three-dimensional full fivedirectional braiding technology, Toray T700S -12K carbon fiber is used as the raw material to manufacture flange joint preform, and to manufacture flange forming by RTM(resin transfer molding) process. As demonstrated by tensile and bending tests, the composite flange joints have better mechanical properties than flanges manufactured by aviation aluminum alloy, and meet requirements of stratosphere truss structure connecting pieces. In conjunction with the results of finite element analysis, mechanical properties can be further enhanced by the improvements of the braiding process, the forming process and the physical dimension.

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Combined experimental and numerical methods were used to study the mechanical properties of multiwalled carbon nanotubes (MWCNTs) enhanced composite T-joints in this article. Herein, an enhanced interface model was created based on the interface mechanical properties with MWCNTs obtained by a flatwise tension test and a single-lap shear test. Then, the finite element model of composite T-joints with MWCNTs was developed with a cohesive zone model to study the damage initiation, evolution, and final failure process of T-joints. Meanwhile, a quasi-static tensile test of the T-joints was carried out to compare with the numerical analysis results. The study results showed that the out-of-plane tensile strength and the in-plane shear strength of MWCNTs enhanced composite increased by up to 26.3%(@3 g/m 2) and 23.4%(@2 g/m 2), respectively. The properties of the filler, which was the weakest part of the T-joints, can be enhanced by adding MWCNTs. The overall bearing capacity of the T-joints was 18.8%(@2 g/m 2 MWCNTs) increase under tensile loading. Predictions given by the FEM of composite T-joints were in good agreement with the experimental results. This article provides a method for analyzing and predicting the complex composite structure enhanced with MWCNTs, which can be used for functional structure design.