Inventory Of Research Hotspots in Aerospace Advanced Composite Materials
Composite materials and metals, polymers, and ceramics are called the four major materials. Today, the composite material industry level of a country or region has become one of the indicators to measure its technological and economic strength. Advanced composite materials are a source of competitive advantage for national security and the national economy. Among them, epoxy resins are excellent reaction-curable resins. In the field of fiber-reinforced composite materials, epoxy resins play a big role. It is compounded with high-performance fiber PAN-based carbon fiber, S or E glass fiber, aramid fiber, polyethylene fiber, and basalt fiber, and it becomes an irreplaceable important matrix material and structural material, which is widely used in electronic power, aerospace, sports Equipment, building reinforcement, pressure pipelines, chemical anti-corrosion and other six fields. This paper focuses on the domestic and foreign status of aerospace advanced resin matrix composites and the problems and directions that China is studying.
Reinforcing fibers used in composite materials
The performance comparison of various fiber materials used in composite materials is shown in Table 1. The properties of some materials were compared. It can be seen from Table 1 that the specific strength and specific modulus of glass fiber alone are increased by 540% and 31%, respectively, compared with metal materials, and the improvement of carbon fiber is even more significant. According to literature reports, the theoretical strength of single-crystal graphite calculated from bond energy and bond density is as high as 150 GPa. Therefore, the further development potential of carbon fiber is very huge. Japan's Toray Company's near-term goal is to make carbon fiber tensile strength of 8.5GPa, modulus 730GPa. Needless to say, carbon fiber will still be the main material for solid rocket motor casings and nozzles in the future.
The development of other applications of carbon fiber composites is very promising, such as aircraft and high-speed train braking systems, civil aircraft and automotive composite structures, high-performance carbon fiber bearings, large blades for wind turbines, sports equipment (such as skis, rackets, fishing rods), etc. . With the expansion of carbon fiber production scale and the gradual decline of production costs, the application of carbon fiber in reinforced concrete, new heating devices, new electrode materials and even daily necessities will also expand rapidly. In order to cooperate with the Beijing Olympic Games, my country plans to vigorously develop new CFRP building materials and new high-tech CFRP markets related to environmental protection and consumer goods.
Carbon fiber is a high-strength, high-modulus material. In theory, most organic fibers can be made into carbon fibers. There are three main types of organic fibers that are actually used as raw materials for carbon fibers: viscose fiber, pitch fiber, and polyacrylonitrile fiber. Most of the carbon fibers used in current solid rocket motor structural parts are made of polyacrylonitrile fibers.
Aerospace resin matrix composites
According to relevant data, every 1 kilogram of the mass of the spacecraft can reduce the weight of the launch vehicle by 500 kilograms, and the cost of a satellite launch is tens of millions of dollars. The high cost factor makes structural materials light in weight and high in performance. The epoxy-based solid engine cover manufactured by the filament winding process is resistant to corrosion, high temperature and radiation, and has low density, good rigidity, high strength and stable size. For example, missile warheads and satellite fairings, heat-resistant materials for spacecraft, and solar cell array substrates are all made of epoxy-based and epoxy-phenolic-based fiber reinforced materials. For the consideration of aerospace flight and its safety, as a structural material, it should have light weight, high strength, high reliability and stability, and epoxy carbon fiber composite material has become an indispensable material.
The reinforcing materials used in high-performance epoxy composites are mainly carbon fibers (CF) and hybrid fibers of CF and aramid fibers (K-49) or high-strength glass fibers (S-GF). The epoxy resin used as the matrix material accounts for about 90% of the high-performance composite resin. The molding process of high-performance composite materials mostly adopts unidirectional prepreg dry layup, and autoclave curing and molding. High-performance epoxy composites have been widely used in various aircraft. Taking the United States as an example, in the 1960s, boron/epoxy composite materials were used for aircraft skins and operating surfaces. Due to the high cost of boron fibers, carbon/epoxy composites were turned to carbon/epoxy composites in the 1970s and developed rapidly. It can be roughly divided into three stages. The first stage is applied to components with little force, such as various control surfaces, rudder surfaces, spoilers, ailerons, flaps, drag plates, landing gear doors, engine covers and other secondary structures. The second stage is applied to structural parts with large load, such as stabilizers, full-motion horizontal tails, and main load-bearing structural wings. The third stage is applied to complex stressed structures, such as fuselage, central wing box, etc. Generally, weight loss can be 20% to 30%. At present, the amount of composite materials on military aircraft has reached about 25% of the weight of the structure, accounting for 80% of the surface area of the body. There are many application examples of high-performance epoxy composite materials in foreign military and civil aircraft.
In addition to ablative composite materials in the aerospace industry, high-performance composite materials are also widely used. For example, after adopting C/EP, the cone of the instrument cabin of the Trident missile can reduce the weight by 25% to 30% and save labor by about 50%. It is also used as instrument support and 55 auxiliary structural parts such as gyro support, ejection cylinder support ring, ejection roller support, inertial device inner support and battery support on the Trident missile. Due to weight reduction, the range is increased by 342km. Shields and interstages for Delta rockets are also manufactured by C/EP. The antennas, antenna brackets, solar cell frames and microwave filters on American satellites and aircraft are all produced by C/EP. C/EP is used to make antenna support structure and large space structure on Intelsat V. The spacecraft Air Voyager uses K-49/EP for the high-gain antenna subreflectors and the inner and outer skins of the honeycomb sandwich structure. The space shuttle uses Nomex honeycomb C/EP composite materials to make large hatches, C/EP tail cabin structural panels, etc.
