The preparation of thermoplastic carbon fiber composites is difficult, so it is necessary not only to select a sizing agent that can improve the interface strength between fiber and matrix, but also to select a reasonable preparation process. At present, the mainstream processes in the industry are molten impregnation method, mud method and so on. No matter what kind of process, the equipment, technology and experience involved are more difficult than thermoset carbon fiber.
Summary of processing technology for continuous carbon fiber thermoplastic composites
However, considering the various performance advantages of thermoplastic carbon fiber composite materials, as long as the level of science and technology can barely meet the preparation standards, I believe that no matter how difficult and complicated, there will be many scholars and institutions competing to try, once the breakthrough, it may become a legend in the material industry.
Among thermoplastic carbon fiber composites, continuous carbon fiber reinforced thermoplastic polymer composites have the best performance, and continuous carbon fiber better inherits the mechanical properties of carbon fiber, so a variety of experiments and attempts in the industry are mostly concentrated here.
Continuous carbon fiber thermoplastic composites can be processed into industrial parts with different shapes but high strength, which can provide a strong help for scientific and technological exploration in aerospace, rail transit, cutting-edge medical and other fields. In order to process continuous carbon fiber thermoplastic composites into the required products, it is necessary to deeply understand the performance of the composite materials, so as to conclude the feasible processing methods.
Summary of processing technology for continuous carbon fiber thermoplastic composites
Continuous carbon fiber thermoplastic composites can be hot-pressed
Since the melting and solidification process of thermoplastic polymers only involves physical changes, there is no need to cure by chemical reaction, which makes thermoplastic composites not only adopt the processing method of thermosetting composites, but also have the possibility of rapid processing. In addition to the basic hot pressing, the thermoplastic carbon fiber composite can also use the stamping process.
1, hot pressing: hot pressing of thermoplastic composite material is the prepreg in the mold after laying, by heating pressure molding technology, hot pressing molding operation is simple, stable quality, is the most widely used thermoplastic composite rapid prototyping technology. At present, it has developed into a mature thermoplastic composite parts manufacturing and processing technology, and has been mature in a variety of models of civil aircraft.
2, stamping molding: stamping molding is a common method of processing and molding continuous fiber reinforced high-performance thermoplastic composite materials. The forming cycle of the stamping process is short (several minutes), and the production efficiency is high. In addition, the stamping process can produce high-strength and high-toughness thermoplastic carbon fiber parts.
Description of the stamping process: First of all, the continuous fiber composite prepreg is cut and laid, and then placed in the oven and heated to about 20~40℃ higher than the matrix melting/softening temperature. The heated multilayer prepreg preform is then quickly transferred to a controlled closing speed press equipped with a specific mold. When the press is closed, the prepreg deforms and fits the mold, where the molten matrix flows under pressure in the mold and fills the mold cavity. After that, a certain pressure is maintained throughout the cooling consolidation process, and when the temperature of the mold is cooled below the melting/softening temperature of the matrix, the matrix will be cooled and solidified rapidly.
Summary of processing technology for continuous carbon fiber thermoplastic composites
Continuous carbon fiber thermoplastic composites can be welded
The thermoplastic carbon fiber composite has a special processing method, welding, because of its thermal remodeling characteristics. Welding process, also known as fusion joining, is an assembly process by using thermoplastic resin as solder, melting and cooling to bond specific surfaces of composite materials.
Thermoset carbon fiber composite materials made of industrial parts, the use of bonding, mechanical connection and embedded, and thermoplastic carbon fiber composite materials have a new choice. Compared with the traditional bonding and mechanical connection, the welding technology is better matched with the matrix, and the welding process is faster and the effect is better.
According to the different heat production mechanism, welding technology can be divided into ultrasonic welding, induction welding, resistance welding and microwave welding. Among them, resistance welding has low equipment requirements, the highest technical maturity, simple energy acquisition, simple and reliable process control, and strong material system applicability, which is suitable for welding of large-size structural parts, so it has been widely used.
Summary of processing technology for continuous carbon fiber thermoplastic composites
Continuous carbon fiber thermoplastic composites can be automatically laid
A major application direction of thermoplastic carbon fiber composite material in the future is aircraft manufacturing, aircraft wings, flaps, tail fins, and surface skin can be made with this material mixed with other materials, which involves an important problem, that is, how to improve processing efficiency?
Whether it is thermosetting or thermoplastic carbon fiber, they have a drawback, that is, batch processing is difficult, and production capacity can not be greatly improved. In response to this problem, scientific research and technical personnel put forward the corresponding solution, that is, the use of automatic laying technology for automatic processing, the use of machines and procedures instead of manual work, liberation of production capacity, to achieve the rapid improvement of processing efficiency.
The principle of automatic laying technology is that the laying head transmits the prepreg wire/prepreg belt at a certain Angle according to a certain movement law, and presses on the die surface by a constant speed roller to achieve automatic laying of composite materials. In the laying process, the prepreg wire/prepreg belt is first heated by a heating device, and then pressure is applied to the prepreg wire/prepreg belt with a press roller. The prepreg wire/prepreg belt is consolidated in situ under high temperature and high pressure environment. The use of automatic laying technology can significantly reduce production costs and shorten processing time. Automatic laying is not limited by the size of the processing site and parts, and the composite material components are formed once in the laying process, which is suitable for the laying and forming of large-size curved components.
Automatic laying processing can complete the work with high repeatability, and according to the upgrade of the program, it can complete the work with higher complexity, but there will still be many bugs in the actual operation, which need to be repaired and repeatedly verified. Laying speed, laying pressure, laying temperature and other parameters need to go through a lot of regulation in order to achieve the desired level of automatic laying.
