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The low-velocity impact finite element model of the carbon fiber-reinforced composite grid sandwich structure was established by ABAQUS. Its panels and grid are both carbon fiber-reinforced composite laminates. The constitutive relation of composite laminates is written into the VUMAT user subroutine using the Fortran language. Simulation of intralaminar failure behavior of composite laminates using the three-dimensional Hashin failure criterion. The quadratic stress criterion and the B-K energy criterion were used to simulate the interlaminar failure behavior, and the delamination damage of the composite panel and the interface debonding damage were simulated. The finite element models of four different types of composite grid sandwich structures, including quadrilateral configuration, triangular configuration, mixed configuration, and diamond configuration, were established. The influence of the single grid width and the height of the grid on the impact resistance of each composite grid configuration was studied. Compared with other geometric configurations, triangular grid sandwich structure provides the best energy absorption characteristics, and T-6-10 has the highest fracture absorption energy (15816.46 mJ). The damage propagation law of carbon fiber-reinforced composite grid sandwich structure under impact load is analyzed.

A water-soluble perylene bisimide derivative, N, N'-di(2-succinic acid)-perylene-3, 4, 9, 10-tetracarboxylic bisimide (PASP) was synthesized by using 3, 4, 9, 10-perylenetetracarboxylic dianhydride and L-aspartic acid as starting materials. The PASP were grafted onto graphitic carbon nitride (g-C3N4) via hydrothermal method to prepare PASP modified g-C3N4 hybrid photocatalyst (g-C3N4-PASP). The composition, structure, morphology and optical properties of the prepared g-C3N4-PASP samples were typically characterized by X-ray diffraction(XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), transmission electron microscopy(TEM), UV-Vis diffuse reflectance spectroscopy(UV-Vis DRS), and solid-state fluorescence spectroscopy. In addition, the photocatalytic activities of the prepared g-C3N4-PASP photocatalysts were evaluated by decomposition of methylene blue(MB) pollutant in water solution under visible light. The results reveal that PASP can be facilely linked to the g-C3N4 covalently via amide bond by hydrothermal treatment; compared to pristine g-C3N4, the g-C3N4-PASP possesses obviously higher specific surface area, dramatic red shifted absorption edge of 614 nm, and more efficient charge separation. Therefore, the visible light photo-catalytic degradation of MB pollution in water over the g-C3N4-PASP is notably improved. The g-C3N4-PASP could degrade 99.4% of MB dyes in 60 min under visible light irradiations (λ >420 nm), with a pseudo-first-order rate constant 2 times higher than that of pristine g-C3N4.

Expanded graphite (EG) based phase change material (PCM) has attracted significant concern in thermal management systems. In this paper, a series of composite PCMs composing of EG with different sizes (50, 80, and 100 mesh) as the substrate, and palmitic acid (PA) as the PCM, were prepared by vacuum impregnation method. The results shown that the size of EG particles effect the adsorption capacity of PA. The mass fraction of PA in PA/EG-50 reached 83.6% and the enthalpy of melting and solidification of PA/EG-50 are 160.13 J/g and 159.75 J/g, respectively. The thermal conductivity decreased slightly as the particle size of EG increased, and the thermal conductivity of PA/EG-100 is the highest of 4.86 W/(m·K). The TGA results show that all composite PCMs present good thermal stability below 200 °C. The electro-thermal conversion efficiency increased with the particle size of EG increasing, and the electro-thermal conversion efficiency of PA/EG-100 reached up to 91.39% under low-voltage conditions (1.9 V). These results throw light on the potential application of EG-based composite PCM, especially for the electro-thermal conversion. [ABSTRACT FROM AUTHOR]