Papers by Keyword: Vacuum Pressure

Abstract: The properties of a composite are depending on the manufacturing process, fiber and its configuration, epoxy used etc. The present research deals with the tensile and wear behaviour of the composites manufactured using Hand Layup (HL) and Vacuum Infusion Process (VIP) with structural and non-structural epoxy combination. 4-layerd (all the layers are oriented in the longitudinal direction) unidirectional CFRP was manufactured using VIP and those results were compared with the HL made samples. The addition of structural epoxy in the resin mixer have shown a significant effect on its fiber volume fraction, tensile and erosion properties. The effect of vacuum pressure in mould cavity on the tensile strength of the CFRP composite was also studied. The morphologies of the CFRP composites made with VIP and HL were studied with the help of the scanning electron microscopy (SEM). The CFRP composites manufactured through VIP have shown a greater tensile strength but it was poor in wear resistance. The addition of structural adhesive to the resin system enhanced the wear resistance. Hence it made the VIP a recommended process for composite manufacturing where both tensile and wear properties are required.

Abstract: An on-line monitoring system of vacuum pressure for 35KV vacuum tube is designed in this paper. The operation principle, hardware structure and software plan are explained in details. The system can valuate the internal pressure of the vacuum tube by monitoring the static charge of the shields using electrical field sensors with rotating electrode. At the same time, the data-collecting machine and the controller are developed for long-range and on-line monitoring. The result shows that such system runs steadily and reliably. It can estimate the vacuum degree accurately laying 35cm from the vacuum tube. Besides, it is steady and anti-jamming with less-cost.

Abstract: The vacuum pressure of vacuum circuit breakers (VCBs) is an important condition to ensure its operational performance, online monitoring of the vacuum pressure of VCBs is an important issue for reducing the accident rate of VCBs and the losses of personnel and property, achieving the intelligence of VCBs. In this paper, 10kV ring network switch cabinet (RNSC) is regarded as the object of study, to achieve its online monitoring. Through analyzing the magnetic field outside the vacuum arc extinguish chambers when the vacuum pressure of VCBs increases, a new method which is based on the comparison of the interphase magnetic field between the corresponding vacuum arc extinguish chambers in RNSCs then monitor the vacuum pressure of VCBs is proposed and demonstrated, and the result established a theoretical basis on the research of the online monitoring system of the vacuum pressure for the vacuum arc extinguish chambers.

Abstract: Sugar palm frond fibre has a potential to be as reinforcement in natural fibres reinforced polyester composites. This paper investigates the tensile properties of sugar palm frond fibre reinforced polyester composites. The sugar palm frond fibres were mixed with polyester composites at the 5 % fibre volume fraction with three different vacuum pressure of 5, 10 and 15 psi. The composites panels were fabricated using a vacuum bagging techniques. The tensile test was carried out in accordance to ASTM D638 respectively. The results showed that the vacuum pressure at 15 psi gave maximum value for tensile strength and tensile modulus. The results indicate that by increasing the vacuum pressure, it created a better bonding between fibre and the matrix. Minitab software was used to perform the one-way ANOVA analysis to measure the significant. From the analysis, there is a significant effect of vacuum pressure on the tensile properties.

Abstract: When the aircraft skin is in the process of trimming and on the flexible vacuum cup fixture, by analyzing the stress to the aircraft skin and studying the relationship between vacuum pressure and deformation of aircraft skin, vacuum pressure, vacuum force and cutting parameters, the relationship which between vacuum pressure of flexible fixture and cutting parameters, clamping points of flexible fixture, friction coefficient of cup and aircraft skin, the maximum deformation allowed on aircraft skin is obtained. It provides a methodology to improve the precision of trimming of aircraft skin components.

Abstract: A new technique for construction of steel tube-confined concrete (STCC), i.e., vacuum-assisted pumping technique was put forward in this paper, and the simulation research both in laboratory and on the building site had been done. The test results showed that the formation of air membrane between steel tube and core concrete could be effectively inhibited by controlling the air content of concrete through optimizing design for mix proportion of concrete and by regulating the vacuum pressure in steel tube during the process of concrete pumping, and thus the density of concrete was increased and the bond between steel tube and concrete was improved. Therefore, the performance of STCC structure such as the ultimate load-bearing capacity was enhanced. Moreover, this new technique can decrease the difficulty of concrete pumping. The technology had been applied in the construction of Yichang Yangtze River Bridge in Yichang-Wanxian railway.

Abstract: The microstructure (i.e., fibre volume fraction, void content, and fibre misalignment) of unidirectional carbon fibre-reinforced polymer (CFRP) composites was optimised by controlling several parameters during manufacture, namely: (i) compressive pressure (0.25~1.25 MPa, in steps of 0.25 MPa), (ii) vacuum pressure (−0.15, −0.20, −0.30, −0.45, and −0.65 MPa), and (iii) holding temperature (100~140 oC, in steps of 10 oC), applied during autoclave curing with the holding time being 30 minutes for all specimens. Optical micrographs captured from cross-sectional, through-the thickness areas, and in-plane areas of the resulting composites were evaluated and analysed in order to describe their microstructural characteristics.