In the carbon fiber industry, the phrase "from raw materials to carbon fibers, the price changes from 1 to 3; processing carbon fiber into composite materials, the price can change from 3 to 10". It is not difficult to see that from carbon fiber to composite materials, the industrial chain is extended, and the added value added is more. Finally, the cost of carbon fiber in composite materials will drop to 20% to 30%.
Carbon fiber fabrics and prepregs are the intermediate links in the development of carbon fiber and are the only way to connect production and application. The development of carbon fiber prepregs is imperative, and it is also an effective means to lengthen the industrial chain and increase the added value of carbon fiber. According to the development experience of Yixing Tianniao and Jiangshan Technology, carbon fiber prepregs and fabrics are new high-performance composite materials, basic materials for defense military industrial enterprises, and advanced alternative materials for future civil industries. The carbon fiber prepreg production line with a width of 1.2 meters introduced by GM can meet the needs of military industry and civil products.
Carbon fiber prepreg products have shown a new development trend in recent years:
1. The advantages of large tow carbon fiber prepreg in the industrial field are prominent. The unidirectional carbon fiber prepreg has a surface density of up to 600 g / m2. This type of heavy prepreg greatly improves the efficiency of the prepreg and subsequent placement process. It is widely used in the field of wind power blades and automobiles.
2. The prepreg of non-autoclave process (OOA, Out of Autoclave) has been vigorously developed. This molding process greatly reduces the time and cost of the subsequent curing of the prepreg. These new prepregs can use the lower cost vacuum bag pressing method, advanced pultrusion method and hot molding method. Products such as Hexcel's HexPly® M 56, Tencate's TC 250, Cytec's Cycom 532, ACG's MTM 44-1.
3. Different prepreg product forms appear. Short-cut prepreg can use economical molding process, products such as Hexcel's He xmc, Dencate's MS series products; semi-prepreg, do not need to completely "wet" fiber during the prepreg process, in the subsequent process Complete infiltration in the middle, products such as Hexfit of He xcel.
4. Special prepreg for different applications. For example, in the automotive field, the requirements for short-time molding of parts are high. In order to meet the subsequent rapid prototyping process, a fast curing prepreg of less than 5 minutes must be developed. Products such as Hexcel ’s Hexply M77 can be cured at 150 ℃ for 2 minutes; Support beam-thick laminate
5. For the production of boards, Gurit has developed SparPregTM, which can obtain laminates with low porosity without compaction and other exhaust fabrics; in the field of composite molds, various companies have also developed corresponding prepreg products, such as Hexcel Hextool, ACG's DFormTM professional products.
6. Prepreg with structure and function. The carbon nanotubes or chopped carbon fibers are mixed in the resin, and then the carbon fiber tow or fabric is infiltrated to form a prepreg with a wave absorbing function.
7. Pre-preg co-cured with other materials. The prepreg can be cured together with the infused resin, it can be molded and cured with SMC, or it can be unidirectional prepreg (fabric prepreg) and SMC.
The above mentioned are all thermoset carbon fiber prepregs. In fact, in recent years, the development of foreign thermoplastic prepregs has been rapid. For example: the German Cetex Institute is engaged in the research and development of manufacturing technology and equipment for semi-finished textile products, functional parts and high-performance structures. It is attached to the Kemnitz University of Technology in Germany. The institute's Ce-Preg® thermoplastic prepreg is a semi-finished fiber composite material formed by continuous fibers and thermoplastic films.
Compared with thermosetting prepreg, thermoplastic prepreg does not require cold storage and transportation. The subsequent molding process is efficient and convenient, the material has high toughness, good impact resistance, and is particularly recyclable. It is in line with energy saving and emission reduction green. Environmental protection trends. However, there are four major problems with thermoplastic prepregs: First, the high viscosity of thermoplastic resins makes it very difficult to infiltrate fibers; Second, there is no suitable low-cost, high-efficiency and quality-prepared prepreg preparation method And equipment; third, the molding temperature of high-performance thermoplastic resin is above 350 ℃, the molding process of prepreg and its composite materials is very difficult; fourth, the price of high-performance thermoplastic resin is too expensive compared with general thermosetting resin. At present, thermoplastic prepregs with different resin mass fraction accuracy are obtained mainly through powder spraying, fiber blending, film rolling and other processes to meet the needs of various molding applications.