1 Analysis of Macro Demand for High-Performance Composite Materials in China
1.1 High-Performance Composite Materials are Key Basic Materials to Meet the Support and Guarantee Needs in the Field of National Security
With their excellent specific strength, specific modulus, high-temperature resistance and good designability, high-performance composite materials are widely used in the national defense and military industry. Taking aerospace as an example, high-performance carbon fiber composite materials are the preferred materials for manufacturing key structural components such as the fuselage and wings of large civil aircraft, accounting for more than 50% of the total mass of the aircraft structure. In the aerospace field, high-performance composite materials are widely used in key components such as rocket engine casings, satellite cabins and solar panels, effectively reducing the structural mass of spacecraft and improving the carrying capacity. In addition, high-performance aramid fiber and ultra-high molecular weight polyethylene fiber composite materials also play an irreplaceable role in military equipment such as bulletproof, explosion-proof and armor protection.
At present, with the continuous advancement of national defense modernization and the acceleration of the upgrading and replacement of weapons and equipment, higher performance requirements have been put forward for high-performance composite materials. Especially in the development of cutting-edge weapons and equipment such as hot-end components of aero-engines and hypersonic vehicles, it is urgent to break through key material technologies such as high-performance silicon carbide ceramic matrix composites and ultra-high temperature ceramic matrix composites to support leapfrog development. Meanwhile, with the continuous improvement of the national defense science and technology industry system, the localization process of key materials such as high-performance aramid fiber, carbon fiber and glass fiber will be further accelerated. It is foreseeable that in the next period of time, high-performance composite materials will play an increasingly important role in safeguarding national strategic security and enhancing national defense strength.
1.2 High-Performance Composite Materials are Key Materials Leading Technological Upgrading
In the civil field, high-performance composite materials also have broad application prospects. Taking the new energy field as an example, large wind turbines have become the mainstream development direction of the wind power industry, and the large-scale development of wind turbine blades is inseparable from the strong support of carbon fiber composite materials. It is estimated that after adopting carbon fiber composite materials, the blade of a megawatt-class wind turbine can reduce weight by 20%~30%, and power output can increase by 5%~8%, with significant comprehensive benefits. In the field of rail transit, car bodies containing composites such as carbon fiber and glass fiber reinforced plastic have become standard equipment for a new generation of EMUs such as the "Fuxing" series. Composites have greatly improved the operating speed, safety and comfort of trains. In addition, in fields such as 5G communication base station radomes, marine engineering and pressure vessels, high-performance glass fiber reinforced plastic and carbon fiber composite materials will also usher in broad market space. Data from the Ministry of Industry and Information Technology shows that since the 13th Five-Year Plan period, under the guidance of the national policy for the development of strategic emerging industries, the overall scale of China's high-performance fiber and composite material industry has grown rapidly at an average annual rate of more than 10%. By 2020, the market demand has approached 30 billion yuan. In the future, with the further improvement of the key material system and the continuous expansion of downstream application fields, the market demand for high-performance composite materials will continue to maintain a rapid growth trend.
1.3 High-Performance Composite Materials are an Urgent Need for China's Green Economic Development
At present, the economic development model oriented towards green, low-carbon and circular development has become a global consensus. In this context, lightweight and environmental protection have become the main direction of transformation and development in many industries. High-performance composite materials have low density and high specific strength, which can significantly reduce product quality while meeting mechanical performance requirements, and have great potential in promoting energy conservation, emission reduction and green development in transportation, construction and other fields. Taking the automotive industry as an example, using carbon fiber composite materials to manufacture car bodies can reduce the overall vehicle weight by more than 50% and fuel consumption by 30%~40%. This is not only of great significance for alleviating energy shortages and reducing air pollution, but also provides important support for China's automotive industry to achieve leapfrog development. It is estimated that if the proportion of carbon fiber composite materials used in China's automobiles reaches 30%, it can save nearly 60 million tons of gasoline per year and reduce carbon dioxide emissions by 170 million tons per year.
In addition, in the field of energy conservation and environmental protection, high-performance fiber-reinforced composite materials are widely used in equipment such as desulfurization towers, dust removal devices and high-temperature flue gas ducts due to their excellent corrosion resistance, aging resistance, thermal insulation and other properties, greatly improving the service life and operational efficiency of environmental protection facilities. It is foreseeable that with the continuous advancement of China's ecological civilization construction and the deepening of the concept of sustainable development, high-performance composite materials will surely play an increasingly important role in promoting the green transformation of industries and building a beautiful China.
2 Development Status of High-Performance Composite Materials in China
2.1 Development Status of High-Performance Fibers
2.1.1 Carbon Fiber
After years of continuous research, domestic carbon fiber has made significant breakthroughs in product types, performance indicators and production scale. T700-grade carbon fiber from key enterprises such as Sinofibers and Guangwei Composites has achieved stable mass production, and its comprehensive performance indicators are comparable to those of Toray Industries of Japan. Meanwhile, the production capacity of carbon fiber precursor at Jilin Carbon Valley has reached 150,000 tons per year, laying a solid foundation for the large-scale development of PAN-based carbon fiber.
In recent years, the planning and layout of the domestic carbon fiber industry have been further optimized, initially forming a new industrial development pattern with the Beijing-Tianjin-Hebei region, the Yangtze River Delta and the Pearl River Delta as the core areas, and the northeast and southwest regions as the two wings. A large number of carbon fiber R&D and production platforms have been built and put into use, providing strong support for the leapfrog development of the industry. Key carbon fiber enterprises represented by Weihai Tuozhan have continued to increase R&D investment to develop T800-grade and M55J-grade high-performance carbon fiber, with continuous improvement in product performance. Emerging enterprises represented by Jilin Jien Magnesium are focusing on the development of low-cost large-tow carbon fiber, leading the industry towards the direction of high performance and low cost.
At present, mainstream domestic carbon fiber enterprises have established relatively complete production process systems and quality management systems, with products covering multiple series such as high-strength, high-modulus, medium-strength and medium-modulus, and large-tow, which are widely used in aerospace, rail transit, new energy and other fields.
2.1.2 Para-Aramid Fiber
In the field of aramid fiber, enterprises such as Yantai Tayho Advanced Materials, Bluestar New Materials and China Aramid Fiber have successfully broken through the technical barriers of industrialized preparation of para-aramid fiber through independent innovation, breaking the monopoly of Japan, the United States and other countries, and meeting the material needs of national defense and military industry, safety protection and other fields to a certain extent. At present, the total domestic production capacity of para-aramid fiber has reached about 33,400 tons per year, showing a year-by-year expansion trend.
However, it must be noted that compared with the international advanced level, domestic para-aramid fiber still has certain gaps in the development of high-end varieties, product quality stability and production cost control. Restricted by factors such as raw material supply, process equipment and market recognition, the operating rate of most enterprises is insufficient, and some production capacity is seriously idle. Overall, the domestic aramid fiber industry is still in the growth stage, and the problem of being large but not strong is prominent. In the future, it is urgent to accelerate the import substitution process of standard-grade para-aramid fiber, strengthen the R&D of high-end products, improve quality stability, reduce production costs, and promote the industrial development towards larger scale and stronger strength.
2.1.3 Glass Fiber
As a traditional reinforcing fiber, glass fiber has a solid industrial foundation and improved supporting capacity after decades of development. At present, China's glass fiber production capacity has exceeded 7.35 million tons per year, ranking first in the world. Industry leaders such as China Jushi and Chongqing International continue to promote the technological transformation of tank furnace wire drawing, and product quality has been continuously improved. Meanwhile, domestic important progress has also been made in the field of special glass fibers such as high-silica and high-strength high-modulus, and a number of high-value-added products have achieved industrialization.
2.2 Development Situation of High-Performance Epoxy Resin and Phenolic Resin for Composite Materials
2.2.1 Epoxy Resin
In the field of epoxy resin, although China has become the world's largest producer and consumer, most products are concentrated in the medium and low-end fields. There are few high-end epoxy resin varieties with unstable quality, and high-purity and high heat distortion temperature epoxy resin for aerospace basically relies on imports. Meanwhile, the modification technology of epoxy resin needs to be strengthened, the development of epoxy prepreg matched with high-performance fibers is lagging behind, and it is difficult to break through common key technologies. These problems restrict the rapid development of the high-performance epoxy resin industry.
2.2.2 Phenolic Resin
Phenolic resin is an important high-temperature resistant resin variety, which is irreplaceable in fields such as carbon/carbon composites for aero-engines. After years of development, China has become the world's largest producer of phenolic resin, and the synthesis and application technology of phenolic resin for glass fiber reinforced plastic is relatively mature. However, in the aerospace field, there is still a large gap between the comprehensive performance of domestic high-end phenolic resin and foreign products, and the batch stability and process adaptability need to be improved. Especially in the molding of large-scale complex components, the required properties such as fast curing and low shrinkage are still difficult to meet. Meanwhile, due to the lack of refined molecular structure design and control means, the development cycle of domestic high-end phenolic resin is long, and the industrialization process is slow.
2.2.3 Special Resins
In terms of special resin matrices, new thermosetting resins such as bismaleimide (BMI) resin, polyimide resin and benzoxazine resin have attracted much attention. Restricted by factors such as raw material synthesis and processing technology, there is still a large gap between the comprehensive performance of domestic special resin matrices and the international advanced level. Taking BMI resin as an example, there are certain gaps between domestic BMI resin and those from the United States, Japan and other countries in key indicators such as monomer purity, molecular weight distribution and thermal stability, and the batch stability needs to be improved.
2.3 Significant Development in the Manufacturing and Application Level of Composite Materials in China
2.3.1 Composite Material Technology
At present, China's high-performance composite material technology has entered a mature stage from the development stage, showing a development trend of multiple varieties, multiple specifications and multiple levels. In terms of material design, it has transformed from traditional "empirical design" to "simulation design" based on multi-scale analysis, and the mechanical properties, process performance and environmental adaptability of composite materials have been significantly improved. In terms of preparation technology, it has developed from hand lay-up molding to automatic, intelligent directions such as automated fiber placement and hydraulic molding, and production efficiency has been greatly improved. Meanwhile, a series of original breakthroughs have been made in common key technology fields such as advanced fiber preform preparation, interface control and composite material recycling.
Benefiting from the progress of preparation technology, China's high-performance composite materials have begun to be applied on a large scale in many fields. Taking the aviation field as an example, when the domestic large aircraft C919 was launched, the proportion of composite materials used in the airframe structure was 12%, which increased to about 50% for the C929, and will be further improved in the future. In the wind power field, complete machine manufacturers represented by Dongfang Electric have successfully applied carbon fiber composite materials to manufacture key structural components, with a maximum single-unit capacity of 26MW. It is foreseeable that in the future, with the continuous maturity of preparation technology, the consumption of high-performance composite materials in aerospace, wind power, rail transit, new energy vehicles and other fields will continue to expand, which will play an important role in accelerating the transformation and upgrading of traditional industries and fostering strategic emerging industries.
2.3.2 Automated Manufacturing Technology of Composite Materials
Automated and intelligent manufacturing is an important development direction of advanced composite materials. In recent years, domestic efforts have been continuously made in the field of advanced composite material molding process equipment such as automated fiber placement, autoclave molding and hydraulic molding, and the localization rate of key equipment has been significantly improved. Taking automated fiber placement as an example, various types of domestic automated fiber placement and tape laying equipment independently developed by units such as China Aerospace Science and Industry Corporation and Commercial Aircraft Corporation of China have been successfully applied in the production of composite materials for key models such as the C919 and J-20. The maximum tape width can reach 300mm, the tape laying speed exceeds 30m/min, and the comprehensive performance has reached the international advanced level.
In process fields such as resin transfer molding and autoclave molding, key enterprises represented by Sinofibers Lianzhong and Tianjin Ruiwei have continuously increased R&D investment, developed various types of domestic complete sets of equipment, and the mass production capacity has been greatly improved. In 2020, the proportion of automated manufacturing of domestic composite material components has reached more than 60%. It is foreseeable that with the continuous expansion of downstream application demand, the level of automated and large-scale manufacturing of composite materials will be further improved, providing strong support for promoting the high-quality development of China's manufacturing industry.
2.3.3 Structural-Functional Integrated Composite Material Technology
In recent years, structural-functional integrated composite materials, as a cutting-edge direction in the field of composite materials, have shown a strong development trend. Taking structural wave-absorbing composite materials as an example, by introducing wave-absorbing functional phases into structural materials, composite materials are endowed with electromagnetic functions, which can realize the organic unity of structural bearing and electromagnetic functions, and have broad application prospects in equipment stealth, electromagnetic protection and other aspects.
At present, units such as the Institute of Chemistry, Chinese Academy of Sciences have successfully developed graphene-modified epoxy resin wave-absorbing coatings, achieving excellent wave-absorbing performance of -12dB in the 8~18GHz frequency band. Meanwhile, important progress has also been made in ceramic matrix wave-absorbing composite materials, and lightweight, broadband and high-efficiency radar wave-absorbing materials have been developed, providing a material foundation for the development and application of a new generation of stealth equipment.
In the field of wave-transparent composite materials, key enterprises represented by AVIC Composite Corporation have successfully developed glass fiber reinforced plastic radomes, which have been applied on a large scale in a number of key aviation equipment. On this basis, a variety of new wave-transparent materials such as carbon fiber reinforced quartz glass composites and ceramic matrix composites have also begun to enter engineering applications. Overall, domestic new breakthroughs have been made in the low-cost preparation and batch stability control of key wave-transparent composite materials, laying a solid foundation for improving the performance of airborne radar systems.
In the field of heat-resistant and ablation-resistant composite materials, units affiliated to China Aerospace Science and Technology Corporation have successfully developed new carbon/carbon composites and ceramic matrix composites, which have passed ground test assessments and their comprehensive performance indicators meet the design requirements. In the field of low-smoke, low-toxic and flame-retardant composite materials, enterprises represented by Sinoma Science & Technology have continuously carried out the development and industrial application of low-halogen flame retardants, with continuous improvement in flame retardant efficiency, and achieved mass application in rail transit and other fields. It is foreseeable that with the increasingly prominent service demand in extreme environments, the R&D and application of high-performance heat-resistant, ablation-resistant, low-smoke and low-toxic flame-retardant composite materials will be further accelerated, promoting China's special composite materials to achieve new leaps.
It should be pointed out that although China has made positive progress in the field of structural-functional integrated composite materials, there are still many shortcomings and deficiencies in links such as basic research, applied research and engineering development. The main manifestations are the disconnection between basic research and applied research, the "last mile" problem in the transformation of scientific research achievements, insufficient multi-functional composite design and simulation analysis capabilities, lack of a multi-scale integrated design platform from fibers and matrices to composite materials, and lagging supporting capabilities such as process equipment and testing and evaluation, which hinder the
