This article reports the longitudinal compressive crashworthiness of three-dimensional four-step circular braided carbon/epoxy composite tubes at temperatures of 23, −50, and −100℃ under strain rate ranging from 340 to 760/s both experimentally and finite element analysis. The experimental results showed that the compression strength, stiffness, and specific energy absorption increased with the decrease in temperature and with the increase in strain rate. It also showed that, the compressive damage morphologies were sensitive to the change in temperature and strain rate. A coupled thermal-mechanical numerical analysis was conducted to find the thermo/mechanical coupling effect on the compressive crashworthiness of the three-dimensional composite tube. The temperature distributions in the braided preform and the resin during the impact compression were also calculated through finite element analysis. From the finite element analysis results, the inelastic heat generation was seen to be more in the preform than the matrix and its distribution and accumulation led to the damage progress along the loading direction.

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Poly (vinylidene fluoride) (PVdF) ultrafine porous fiber membranes with a three-dimensional network structure, high porosity and electrolyte uptake are prepared via a blend electrospinning and phase separation process under ultrasonic-assisted vibration. The structure and morphology of PVdF fiber membranes are investigated by the scanning electron microscope and porous structure parameter analyzer. The electrochemical performances of supercapacitor constructed with PVdF ultrafine porous fiber membrane as separator-cum-electrolyte are investigated. PVdF ultrafine porous fiber membranes possess high electrolyte uptake (360 wt%) and wide electrochemical stability windows (0.0 to 3.3 V). The activated electrode supercapacitor constructed by PVdF ultrafine porous fiber separator-cum-electrolyte exhibits superior specific capacity (39.5 F·g−1) even under high current density (100 mA·g−1).