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Resin matrix composites (RCs) have better thermal and chemical stability, so they are widely used in engineering fields. In this study, the aging process and mechanism of two different types of resin-based three-dimensional four-way braided composites (H15 and S15) under different hygrothermal aging conditions were studied. The effect of aging behavior on the mechanical properties of RCs was also studied. Three different aging conditions were studied: Case I, 40 °C Soak; Case II, 70 °C Soak; and Case III, 70 °C-85% relative humidity (RH). It was found that the hygroscopic behavior of RCs in the process of moisture-heat aging conforms to Fick's second law. Higher temperatures and humidity lead to higher water absorption. The equilibrium hygroscopic content of H15 was 1.46% (Case II), and that of S15 was 2.51% (Case II). FT-IR revealed the different hygroscopic mechanisms of H15 and S15 in terms of aging behavior. On the whole, the infiltration behavior of water molecules is mainly exhibited in the process of wet and thermal aging. At the same time, the effect of the aging process on resin matrices was observed using SEM. It was found that the aging process led to the formation of microchannels on the substrate surface of S15, and the formation of these channels was the main reason for the better moisture absorption and lower mechanical strength of S15. At the same time, this study further found that temperature and oxygen content are the core influences on post-aging strength. The LVI experiment also showed that the structural changes and deterioration effects occurring after aging reduced the strength of the studied material. [ABSTRACT FROM AUTHOR]

The electronic and transport properties of a series of covalently functionalized graphene sheets m (FeBz) n -G (m , n = 1, 2) are calculated by density functional theory (DFT) and the nonequilibrium Green's function (NEGF) methods. All the studied systems are chemically stable due to the d – π interaction between Fe and graphene. Addition of (FeBz) n (n = 1, 2) introduces a half-metallic behavior: the up-spin state degradates into a semiconductor channel while the down-spin state behaves as a metallic channel. Particularly, two-fold anisotropy magnetism could be obtained, with the ferromagnetic ordering extending either parallel to the graphene plane originated from the Fe- d up-spin state or perpendicular due to the d -electron coupling along the Fe-Bz-Fe-Bz chain in the down-spin state. Because of the trapping effect, attaching (FeBz) n decreases the conductivity. Anisotropy inherited from graphene after functionalized with (FeBz) n (n = 1, 2): zigzag direction has higher conductivity than armchair direction. The number and alignment style of (FeBz) n (n = 1, 2), and the spin-polarized character, all have impacts on the transport property. Our findings provide useful guidelines for achieving graphene-based electronic and spintronic nanodevices by attaching other similar long multi-decker metal-arene systems. [Display omitted] • Electronic and transport properties of functionalized graphene m (FeBz) n -G (m , n = 1, 2) are calculated theoretically. • Addition of (FeBz) n (n = 1, 2) introduces half-metallic behavior. • Ferromagnetic ordering extends not only parallel to the graphene plane but perpendicular to it. • Conductivity is determined by anisotropy inherited from graphene, number and alignment of (FeBz) n , and spin polarization. [ABSTRACT FROM AUTHOR]