RESUMEN
The tack of prepreg is a key factor affecting the automatic tape laying process. During the manufacturing process of large composite parts, prepreg material may be stored at room temperature for several days, resulting in a decrease in its tack. In this study, a new tack test tool was designed, and the decay rate of prepreg tack at different temperatures was tested. We proposed a prepreg tack decay model, which assumes that the main factor in tack decay is the reduction in resin chain activity during storage. The maximum deviation between the model calculation results and the experimental results of the tack decay rate is 9.7%. This study also proposed a new statistical unit for prepreg tack, which can establish the relationship between the tack of prepreg and its remaining storage time and reduce prepreg management costs.
RESUMEN
In order to promote the application of composite insulators in coastal areas with high temperature, high humidity and high salt, it is of great importance to develop matrix resin with salt corrosion resistance for composite core rods. In this study, bisphenol A epoxy resin was modified by blending with alicyclic epoxy resin (2021P). Three different proportions of 2021P/DGEBA blend resins (0% 2021P/DGEBA, 10% 2021P/DGEBA and 20% 2021P/DGEBA) were prepared, and the high salt medium corrosion test was carried out. The physicochemical (FTIR, DMA, TGA) and electrical properties (dielectric loss, leakage current and breakdown field strength) of the blend resin before and after aging were tested and analyzed, and the optimal blend proportion was determined. The results showed that after salt aging, the Tg of 0% 2021P/DGEBA decreased to 122.99 °C, while the Tg of 10% 2021P/DGEBA reached 134.89 °C; The leakage current of 0% 2021P/DGEBA increased to 48.994 µA, while that of 10% 2021P/DGEBA only increased to 44.549 µA; The breakdown field strength of 0% 2021P/DGEBA dropped to 40.36 kv/mm, while that of 10% 2021P/DGEBA only dropped to 43.63 kv/mm. The introduction of 2021P enhanced the salt corrosion resistance of the blend resin, which could hinder the penetration, diffusion and erosion of external media (such as Na+, Cl-, H2O, etc.) to the matrix resin. The comprehensive properties of 10% 2021P/DGEBA blend system reached the best, which was better than other blending resins, showing great application potential.
RESUMEN
With the application of the composite cross-arm in power systems, comprehensive anti-aging performance is a key factor to determine whether it can operate safely. In order to study the influence of the operating environment on the external insulation characteristics of composite cross-arms of distribution networks, various aging conditions such as voltage, rain, temperature, humidity, salt fog and ultraviolet light were simulated in a climate chamber based on the real operation conditions of the 10-kV composite cross-arm. A multi-factor aging test of composite cross-arms with two kinds of cross-section shapes (T-shaped and square) was carried out for 5000 h. The change trends of leakage current and flashover voltage of the composite cross-arms before and after aging were analyzed. Finally, the aging mechanism of the silicone rubber sheaths was analyzed to further explain the reasons for the change of external insulation performance of composite cross-arms. The results show that the leakage current rising rate of T-shaped and square composite cross-arms after aging increases significantly, and the minimum flashover voltage decreases to 58.3 kV and 49.502 kV, respectively. The results of FTIR, SEM and hydrophobic angle tests show that, after aging, the performance of the silicone rubber outer sheath material decreases in varying degrees. In general, UV aging has the greatest influence on the external insulation characteristics of composite cross arms. Generally speaking, after 5000 h of multi factor aging, although the external insulation characteristics of the 10-kV composite cross-arm decreases to a certain extent, there is still enough margin to meet the normal operation.
RESUMEN
This article proposes a novel active localization method based on the mixed polarization multiple signal classification (MP-MUSIC) algorithm for positioning a metal target or an insulator target in the underwater environment by using a uniform circular antenna (UCA). The boundary element method (BEM) is introduced to analyze the boundary of the target by use of a matrix equation. In this method, an electric dipole source as a part of the locating system is set perpendicularly to the plane of the UCA. As a result, the UCA can only receive the induction field of the target. The potential of each electrode of the UCA is used as spatial-temporal localization data, and it does not need to obtain the field component in each direction compared with the conventional fields-based localization method, which can be easily implemented in practical engineering applications. A simulation model and a physical experiment are constructed. The simulation and the experiment results provide accurate positioning performance, with the help of verifying the effectiveness of the proposed localization method in underwater target locating.
