' Carbon fiber industry chain core links are many, including upstream raw silk production, the middle reaches carbonization link, downstream composite material and its application, after more than 10 years of research and development and breakthrough, at present our country carbon fiber's ' kabozi ' problem mainly in the downstream application link, namely the composite material and the product aspect.
' China Chemical Fiber Industry Association vice President He Yanli said. Carbon fiber is a carbon content in more than 95% of the high strength of the new fiber material, the reason its quality than the metal aluminum light, but the strength is higher than steel, but also capable of high-temperature, corrosion resistance, fatigue resistance, creep and other characteristics, one of the key composite auxiliary material is epoxy resin. Epoxy resin has excellent physical and electrical insulation properties, strong adhesion, can be bonded together carbon fiber.
But the current domestic production of high-end carbon fiber, the use of epoxy resin are all imported.
The difficulty of modifying the fragile epoxy resin According to the mechanical properties of carbon fiber can be divided into high-strength, ultra-high-strength, high modulus and ultra-high modulus type. In Japan Toray Company product Code, T refers to the cross-sectional area of 1 square centimeters of the number of units of the carbon fiber can withstand the tensile tonnage, that is, the higher the number of T, carbon fiber quality is better; modulus refers to the tensile modulus of external tension or pressure to restore the original shape.
At present, China has been able to produce T800, such as higher carbon fiber, but Japan Toray mastered this technology in the last century of the 90 's. Zhang Dingjin, chairman of China Composite Material Group Co., Ltd., said, compared to carbon fiber, China's high-end epoxy resin industry lags behind the international situation is even more serious.
Especially used in aircraft, aerospace and other fields of high-end carbon fiber.
Molecular structure containing epoxy group is collectively referred to as epoxy resin, in addition to carbon fiber, but also widely used in machinery, electronics, home appliances and civil engineering and other fields. High-end epoxy resin dependence on imports on the one hand and China's chemical industry is weak, on the other hand with the characteristics of epoxy resin. A molecule chain has more than two multiple functional groups of molecules, can be cross-linked reaction and form insoluble, not fused with three-direction reticular structure of the polymer.
The use environment of aeronautical structural parts is extremely harsh, carbon fiber composite materials must be able to withstand the long-term high temperature of hundred degrees Celsius and minus dozens of degrees Celsius at low temperatures, at the same time, under hot and humid conditions of glass transition temperature, elastic modulus and compressive strength can not be significantly reduced, this requires more senior officials can, epoxy value and viscosity of the appropriate products. The number of functional groups that can participate in a reaction in a molecule is called a functional, and some in the industry say it is not as high as the senses. The energy level is too high, the composite will be too hard and ductile.
Therefore, it must be specific to the use of different conditions, considering the intensity, modulus, toughness, high and low temperature, fatigue, etc., from the formula system, molecular structure to analyze, this is a very complex system work, and high technology content, research difficult.
Lack of intelligent automation equipment The greatest threat to the performance of continuous carbon fiber reinforced composites is the low velocity impact delamination damage of composites, which is also the core of the application of high-performance composites in aircraft structures.
One of the main reasons for the sensitivity of composite to impact delamination is that the toughness of epoxy resin is insufficient. In order to meet the requirements, the compressive strength (CAI value) of the toughened composite after impact must reach at least 200-300 MPa. At present, the internationally accepted resin toughening method includes in-situ particle toughening or off-position intercalation toughening. ' The relationship between the molecules is very complex, it is very difficult to develop successfully without long-term research foundation and many years experiment to finally achieve the rigid toughness.
' Resin Association Epoxy branch secretary General Kongzhenwu said. The modification of epoxy resin is also closely related to intelligent automation equipment.
Yumu, a professor of materials science and engineering at Donghua University, said that the short production time of carbon fiber in China, the lack of low-cost complete sets of automated production equipment, resulting in low production efficiency, product stability, and so on. ' It is also necessary to increase the development and production of such intelligent equipment.
' said He Yanli.
The application of traction is not enough progress slow Special epoxy resins, ' different uses, their structure and performance are different.
' Kongzhenwu said that the production and application of carbon fiber materials in China are disconnected, the use of traction is insufficient, there is no feedback correction, such as epoxy resin technology progress naturally slow. At present, the most high-end carbon fiber used in aircraft, such as on the Boeing B787 model, the use of toray production of carbon fiber composites has accounted for 50% of the total material consumption.
2016, Toray Company's carbon fiber production of about 40,000 tons, and China's carbon fiber enterprises more than 30, total capacity of 20,000 tons, the actual production of about 7000 tons. Toray Carbon Fiber The massive use of Boeing is by no means an overnight feat. Since the 80 's, Toray has cooperated fully with Boeing, and Toray has even lived in Boeing, designing and producing carbon fiber according to Boeing's requirements.
Until 2011-2012, the use of carbon fiber aircraft began flight test, running-in time for nearly 30 years, and according to Boeing's use of the requirements and feedback, constantly correcting, correcting products. Furthermore Once the leading effect is formed in an industry, it is difficult to surpass it. The current Boeing aircraft, the United States F-22 and F-35 fighters used in carbon fiber epoxy resin are from the United States Heinz Company. Yumu said, Huntsman products have already passed the material and process certification, if you want to use other enterprises to produce epoxy resin, but also need a long, complicated argumentation process, carbon fiber production enterprises are willing to use the Huntsman.