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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]

Abstract The understanding of dynamic damage and failure of thermo-oxidative aged 3D carbon fiber/epoxy braided composite is critical to its durability design. Here we aim at a fine description of damage and failure of aged composites under impact compression by means of experiment and finite element analysis (FEA). The composites and epoxy resins were aged in air at 110 °C, 130 °C and 150 °C for prescribed time, respectively. The failure processes were recorded with high-speed camera. We found that with the increase of ageing temperature, the interface damage becomes more serious and the epoxy resins tend to a rubbery behavior. For the composites aged at lower temperature (110 °C), the impact resistance degradation is mainly attributed to the degradation of epoxy resin. While interface degradation is found to be the dominant degradation mechanism when the composites aged at higher temperature (130 °C, 150 °C). FEA results showed that in the process of impact, the plastic deformation induced temperature and thermal stress of the aged composites decrease compared with the unaged composite. For the unaged composites and the composites aged at lower temperature, the damage of reins is the main factor that affects the energy absorption of fiber tows. The interface damage plays a more important role in the energy absorption of fiber tows when the composites aged at higher temperature. [ABSTRACT FROM AUTHOR]

Abstract When serving as a lightweight structural member in many areas, the dynamic mechanical behavior of fiber-reinforced polymeric matrix composites, especially under different strain rates, means a lot to the optimization of structure design as to high-speed impact. Under different loading rates and directions, we experimentally and numerically investigated the strain rate effect on the impact compressive behavior of 3-D angle-interlock woven composites (3-D AWCs) composed of carbon fiber and epoxy resin. Based on the factual geometrical architecture of 3-D AWC, the meso-scale model, which considers the interfacial damage between the reinforcements and matrix, was established to visually characterize the deformation history and damage morphologies of 3-D AWCs during impact compression process. Further, we performed high strain rate compressive tests on the split Hopkinson pressure bar (SHPB) apparatus integrated with a high-speed photography system for capturing images of progressive damage process to validate the proposed mesoscopic model. The stress-strain curves of various strain rates show strain rate effect varies depending on loading direction. The rate sensitivity on the compressive failure strength exists at weft direction and through-thickness direction except for warp direction. Moreover, both from images and finite element model results, the localized adiabatic shear band induced by intense plastic strain, initiates mainly from epoxy resin matrix and propagates along the interface at all three loading directions. [ABSTRACT FROM AUTHOR]

• Modified metal-organic framwork are applied to improve the radiation resistance of epoxy resins and investigate the anti irradiation mechanism of metal-organic framework. • UIO-66-OH nanoparticles can effectively improve the tensile modulus and thermal stability of epoxy resin. • 88.7% reduction in free radical concentration of UIO-66-OH / EP composite compared to epoxy resin. Understanding the degradation mechanism of epoxy resin under irradiation and enhancing the radiation resistance of epoxy resin are of great significance for its application in aerospace and nuclear industries. In this study, we investigated the radiation resistance of epoxy reinforced by UIO-66-OH metal-organic framework. Outstanding radiation resistance was achieved by using UIO-66-OH nanoparticles as radical scavengers to retard epoxy degradation. The introduction of UIO-66-OH reduces the content of free radicals generated after irradiation by 88.17%. UIO-66-OH also improves the mechanical and thermal properties of epoxy before and after irradiation. The scavenging radicals mechanism of hydrogen atom transfer of UIO-66-OH is more dominant than that of graphene oxide and carbon nanotubes. The radiation resistance of UIO-66-OH nanoparticles is related to hydroxyl functionalization and porous structure. This work provides a new idea and method for improving the stability of epoxy resin under gamma ray radiation. [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]

The steel fiber textile overcomes mostly the shortcomings of traditional reinforcement materials. However, the poor corrosion resistance severely limits service life. In this study, based on the mechanism of stress corrosion and electrochemical corrosion, the epoxy resin anti-corrosion coating was designed and prepared. First, the von Mises stress distribution of lamellar and spherical fillers in epoxy resin was studied by finite element simulation, which confirmed that the stress distribution of spherical SiO 2 filler was more uniform when it was stressed. In addition, to optimize the dispersion of spherical SiO 2 in epoxy resin, the spherical polyaniline@SiO 2 (PANI@SiO 2) composites with core-shell structure were produced with in situ polymerization method. Ultrasonic C scanning results showed that the addition of PANI@SiO 2 nano-filler can effectively reduce the defects in epoxy resin. Compared with bare steel fiber, the composites coating of 2 wt% PANI@SiO 2 /epoxy showed the most excellent resistance to stress corrosion and electrochemical corrosion. The capacitance diameter is two orders of magnitude higher, which has good stability in simulated concrete pore solution. This is due to the fact that the addition of PANI@SiO 2 nanomaterials improves the physical shielding properties of epoxy, creating a labyrinth effect, and that PANI can produce passivation on the metal surface. • The finite element results showed that the spherical filler could improve the stress corrosion resistance of the epoxy composite coating. • Spherical PANI@SiO 2 composites with core-shell structure were successfully prepared, and the coating rate of PANI reached 21.04 %. • The addition of PANI@SiO 2 nanofillers could effectively reduce the defects in the epoxy resin. • The impedance spectrum of the 2 wt% PANI@SiO 2 /EP anticorrosive coating was 6 × 105 Ω/cm2 and showed good stability. [ABSTRACT FROM AUTHOR]