The process of forming carbon fibre products in a hot press comprises the following steps: pre-compaction of the mould lay-up, placing the laid-up components in the hot press, testing the vacuum tightness, curing and natural cooling; wherein the pre-compaction consists of laying down the prepreg, release cloth, one-way breathable film, breathable felt and vacuum bag film auxiliary material in turn on the mould; curing consists of laying down the prepreg, release cloth, one-way breathable film and vacuum bag film auxiliary material in turn on the mould; curing consists of laying down the prepreg, release cloth, one-way breathable film and vacuum bag film auxiliary material in turn on the mould. The curing process is carried out at a temperature of 60 to 200 r, a pressure of 1 to 6 bar and a curing time of 3 to 12 h. The carbon fibre products are obtained.
The hot press can process, as one of the methods of forming carbon fibre composite components, is also used in large numbers by many manufacturers of carbon fibre composite parts. By the hot press can process of composite products accounted for more than 50% of the overall production of composite products, the proportion of the aerospace sector is as high as 80%. In addition, in the electronics, weapons, transportation, sports equipment and new energy and other high-tech fields also have a wide range of applications.
Hot press tank forming is suitable for composite structures, honeycomb sandwich structures and metal or composite glued structures in the forming. It generally has the advantages of high precision of temperature and pressure control, safe and reliable structure, stable forming process, low energy consumption, simple operation and maintenance, etc. It is suitable for both large and complex type surfaces, plates and shells, as well as simple shaped plates, rods, tubes and blocks, and can also be used for gluing and assembling, and small pieces can be cured in multiple pieces at the same time.
The production process of the carbon fibre box is roughly the same: the carbon fibre prepreg is laid on the mould according to the lay-up requirements, after which the carbon fibre box is to be positioned on the mould for assembly and encapsulated in a vacuum bag. The encapsulated carbon fibre product is placed in a hot press tank. Under vacuum, after the procedures of heating up, pressurising, holding, cooling and unpressurising of the hot press tank equipment, the curing is achieved using the uniform temperature and uniform pressure provided simultaneously in the hot press tank, thus allowing the formation of carbon fibre composite parts with high surface and internal quality, complex shapes and huge areas.
Even if different carbon fibre products use the hot press can process, the methods and steps are similar, basically following the sequence of laying down the blank, making a vacuum bag, vacuum leak detection, entering the can, opening the heating procedure, pressurisation, holding pressure, lowering the temperature, lowering the pressure and stopping, and discharging the workpiece from the can, the main difference being the difference in the mould and the process parameters set according to the required properties of the product. After curing and demoulding the carbon fibre products can be inspected for appearance quality by visual inspection and gauging, non-destructive testing with the aid of ultrasound, X-ray, infrared etc., destructive testing by microscopic observation and sampling tests.
It is worth noting that inert gas pressurisation should be used when the temperature inside the tank is higher than 150°C or the pressure is greater than 1MPa. After the hot pressurised tank has started to pressurise, there is a possibility that the vacuum bag may leak, and when this is encountered, it should be dealt with according to the actual situation. If it is a slight air leakage, it is allowed to continue curing, and the use of atmospheric measures to slow down the rupture of the vacuum bag, in serious cases should be stopped to repair.
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