Carbon fiber products processing process and prospect discussion

Carbon fiber is used in aerospace and military, sporting goods, automotive industry products has been widely known, with the development of carbon fiber large filament bundle and the decline of carbon fiber prices, some new markets are developing rapidly. At present, carbon fiber has been listed as a key new product supported by the national chemical fiber industry, and has become a hot spot for research and development in the domestic new material industry, so carbon fiber composite materials have a good prospect of development and application.

Carbon fiber is a kind of fibrous carbon material with carbon content above 95%, usually combined with resin, metal, ceramic and other matrix as composite materials, generally not used alone, compared with traditional metal materials, carbon fiber density is only 1/5 of steel, while the strength can reach 7-10 times of steel, where epoxy resin-based carbon fiber composites are widely used in the automotive industry, rail transportation, medical equipment In addition, carbon fiber materials are also widely used in petroleum, metallurgy, textile and other fields. Due to the limitation of domestic technical capacity, China is still dependent on the import of high-end carbon fiber materials, and the formation of domestic deep processing phenomenon. At present, there are thousands of domestic manufacturers engaged in carbon fiber composite products, but due to the capacity production, carbon fiber products still need to be imported in large quantities. According to relevant reports, in the first half of 2014, China's imports of carbon fiber and products amounted to 5513.2 tons, with annual imports of about 10,000 tons, and the import dependency still hovers at a high level.

The reason for this is that China's carbon fiber production and downstream product manufacturing technology still lags behind that of the United States, Japan and other European and American countries. At present, the domestic carbon fiber composite molding process mainly includes hand paste molding process, winding molding process, pultrusion molding process, resin transfer molding process and molding process. The resin transfer molding process (RTM) is a common molding process used by domestic carbon fiber downstream manufacturers, and the molded parts have excellent performance and are suitable for annual production of about 50,000 sets. It is recognized as a low-cost composite molding technology in the world. The technology is developing rapidly and has been widely adopted in the automotive industry. For example, Wuxi VIA New Material Technology Co., Ltd. manufactured an I-shaped carbon fiber structural part for China CNR Group. The structural part is 780mm long, 42mm waist height, 6mm waist thickness, 52mm leg width, tested strength far exceeds the original I-beam, and the weight is only 750g, effective weight reduction of 62%, the part has the advantages of acid and alkali resistance and other corrosion, low density, long life, etc., for the development of lightweight trains to produce greater economic benefits.

In addition, vacuum bagging is also one of the processes of carbon fiber composite products production, the main advantage of this process is the use of ordinary wet lay-up technology, usually can obtain high carbon fiber content of composite materials, epoxy resin can be better impregnated with carbon fiber. The main disadvantage is that the additional process increases the labor and cost and requires a high level of operator skill and low production efficiency. The hand paste molding process, it is in turn in the mold cavity surface coated or layered release agent, gel coat, moderate viscosity of epoxy resin (gel coat gel after coating) and carbon fiber, hand-held rollers or brushes to make the epoxy resin impregnated carbon fiber, and to drive out the air bubbles, and compact the base. The operation is repeated several times until the designed thickness of the product is reached. The main advantages of this process are room temperature molding, low investment in equipment, low depreciation of the mold, and the ability to manufacture large products. The main disadvantages are that it is labor-intensive, the quality of the products is determined by the skill of workers, and the resin used for hand gluing is low in molecular weight, which may be harmful to human health and safety than the resin with high molecular weight.

The manufacturing technology of carbon fiber composite products involves three aspects: material, design and technology, and these three aspects influence each other and are indispensable. After nearly 40 years of research, application and development of domestic carbon fiber materials, although great progress has been made, the development progress is still worrying due to the cost and recycling factors. From the current point of view, in addition to the cost factor, the production and manufacturing of carbon fiber composites are different from traditional metals, both in terms of structural design, material selection and process manufacturing lack of experience and data accumulation, as well as the lack of new design standards. In addition, only when the recycling problem is completely solved, carbon fiber composites can reduce the cost and be widely used.

With the further development of carbon fiber preparation technology and carbon fiber surface treatment technology, the comprehensive performance of epoxy resin/carbon fiber composites will be improved, which will greatly promote the development of epoxy resin/carbon fiber composites and effectively broaden the application fields of epoxy resin/carbon fiber composites. At present, the country has strengthened the attention and support to carbon fiber industry at the strategic level, and built a platform to promote the upstream production process improvement and downstream manufacturing and application by vigorously carrying out the cooperation mode of industry-academia-research.