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The serious damage caused to 3D braided carbon fiber (CF)/epoxy (EP) composites in high-energy irradiation environments is a pressing research topic that has not yet been reported. This study analyzed the γ-irradiation multi-scale damage of the matrix, interfaces, and near-interface regions in 3D braided CF/EP composites with three different braiding angles (18°, 28°, 38°) at atomic, microscopic, and macroscopic scales. The molecular structure and atomic charge information alterations of epoxy matrix were characterized using soft X-ray absorption spectroscopy (sXAS). When the irradiation dose reached 1000 KGy, the compressive strength of composites decreased by 20.88 %, 18.07 %, and 16.60 %, respectively, with an increase in the braiding angle. Micro-CT observation, along with statistical computing, confirmed that irradiation causes interface damage and increases the defect volume of 3D braided composites. Nanoindentation was used to compare the modulus of carbon fiber, interface, near-interface regions and matrix in irradiated composites and the function of CF/resin interface as an irradiation defect capture site in the irradiation resistance of resin-matrix composites has been newly established. In addition, the mechanism behind the effect of braiding angle on macroscopic properties was also analyzed. [Display omitted] • The braided structures exhibited varying responses to irradiation, with 3D-38° showing the highest performance retention. • Soft X-ray absorption spectrometry was developed to characterize the valence changes of oxygen and carbon in irradiated resin. • Interface as an irradiation defect capture site consumes most of the energy and reduces the damage of resin near the interface. [ABSTRACT FROM AUTHOR]

The silanized graphene oxide (KH-GO) with different mass fractions was dispersed in epoxy resin by a solution blending method and resin transfer molding process. The nano indentation method was used to test the micromechanical properties of GO/epoxy composites with different mass fractions, and the effect of GO on the hardness of epoxy matrix composites was quantitatively determined, and the influence of adding KH-GO on the thermal mechanical and bending properties of epoxy resin was discussed by dynamic thermal mechanical and universal strength machine tests. The experimental results show that the thermal and mechanical properties of composites are improved with the increase of the amount of KH-GO. Especially, when the content of KH-GO was 0.3%, the bending strength (125.4 MPa), hardness (281.0 MPa), and glass transition temperature (99.6°C) of composites reached the highest. It was proved that the composites showed its excellent performance and the silane coupling agent was successfully grafted to the graphene oxide by covalent bond, which effectively improved the interface compatibility of the reinforcing body and the matrix and was related to good dispersibility in the epoxy resin. This method is simple and effective, providing a certain reference value for the enhancement of the mechanical properties of the next generation of nanocomposites. [ABSTRACT FROM AUTHOR]