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Polyimide@graphene oxide (PI@GO) composites were prepared by way of a simple solution blending method. The nanoscale hardness and Young’s modulus of the composites were measured using nanoindentation based on atomic force microscopy (AFM). A nanoscale hardness of ~0.65 GPa and an elastic modulus of ~6.5 GPa were reached with a load of ~55 μN. The indentation recovery on the surface of PI@GO was evaluated. The results show that relatively low GO content can remarkably improve the nanoscale mechanical properties of PI.

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Filament-wound Composite Pressure Vessels (FCPV) have been used widely in the aerospace and commercial industries. Multi-type FCPVs have been applied to different mission scenes. In this paper, four types of domes (helical winding, helical winding ellipsoid, polar winding, polar winding ellipsoid) are studied based on a simplified parametric model, and a modified meridian computing method is employed for polar and helical winding domes after the inflection points. At last, four FCPV cases of different type of domes are calculated and discussed in detail. Results indicate that the parameters of the same winding pattern dome are similar, so it is suggested to use ellipsoid domes in prior for the convenience of fabrication and avoiding the inflection point at the meridian.

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Abstract-In this paper, a novel wideband quasi-Yagi antenna is proposed and investigated for multiple-input multiple-output (MIMO)/diversity antennas applications. An aperture-coupled balun is adopted with a curved Yagi radiator for the antenna to realize wideband property. The proposed quasi-Yagi antenna has high radiation efficiency and stable end-fire radiation patterns, operating in a wide bandwidth from 7 to 13.8 GHz. Then a pattern diversity antenna is developed using two elements, which are overlapped partly and placed in opposite orientations. The measured 10-dB bandwidth of the MIMO antenna is from 6.3 to 13.6 GHz. Meanwhile, isolation between the two ports is better than −26 dB. The radiation patterns and envelope correlation coefficients are also presented. The proposed pattern diversity antenna is validated to perform stable behaviours over a wide bandwidth, and it will find applications in wireless communications and radars systems.

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