(For the report, please log in to the Future Think Tank www.vzkoo.com)
1. Analysis of the investment value of the military composite materials industry chain
my country's military composite materials industry is currently in the growth stage, and we believe that the overall profit level in the future is expected to show a continuous upward trend. According to the industry's life cycle theory, the industry needs to go through four stages: infancy, growth, maturity and recession from its appearance to its complete withdrawal from social and economic activities. The development of military composite materials technology has gradually matured, and it is more and more widely used in weapons and equipment, and the application proportion is getting higher and higher. For example, the application of fourth-generation machine composite materials in my country has reached 20%. With the development of downstream military industry, the demand for military composite materials is expected to increase rapidly, and more and more enterprises are engaged in the research, development and production of military composite materials. The military composite materials industry currently has the characteristics of rapid growth in demand, gradually becoming standardized, industrial competition situation is becoming more and more advanced, and enterprise entry barriers are relatively high. In combination with the characteristics of industrial cycle development, we believe that the military composite materials industry is currently in the growth stage, and industry enterprises have high profit margins and strong market demand.
The development process of military composite materials is a process of constantly breaking through foreign blockades and is one of the industries that the country has focused on supporting and encouraging development in recent years. Due to the special application fields of carbon fiber , quartz fiber , silicon carbide fiber and their composite materials, and the performance of weapons and equipment has been significantly improved. At the beginning of development, they all faced foreign technology and equipment blockades, which led to relatively difficult initial development. After a period of technological accumulation, a rapid breakthrough was achieved under the support and guidance of major national plans and policies.
my country's military composite material technology has been developing for many years and has already had a good foundation. In the future, with the gradual implementation of these special plans, it is expected to further accelerate the technological improvement and application promotion of composite materials.
...
2. The composite material has excellent performance, and more and more applications are used in the domestic and foreign defense fields.
Composite material technology complements the development of weapons and equipment. my country still has a lot of room for improvement.
Composite material refers to a new material composed of several different materials such as organic polymers, inorganic non-metals or metals through composite processes. It can not only retain the main characteristics of the original component materials, but also complement the performance of each component through material design, and correlate and coordinate with each other, thereby obtaining superior performance that is incomparable to the original component materials.
composite material was mainly used as functional parts in the early days and can now be used as the main bearing structural parts. composite materials have been used in military equipment since the 1960s and have temporarily emerged. In the early days, due to their high prices, low output and low performance, they were mainly used as functional parts and have not used much. For example, during this period, glass fiber reinforced composite materials began to be used in fairings, flaps, ailerons and other positions in military aircraft; the US "Polaris" strategic missile began to use fiberglass composite materials; and the deck chambers of patrol gunboats also began to use composite materials. With the improvement, development and innovation of design/manufacturing technology, the cost of composite materials has been declining, the performance has been continuously improved, and the production scale has been continuously expanded. It has now been used as the main bearing structural component and has gained important applications in many military industries such as aviation, aerospace, weapons, and ships.
With the continuous development of weapons and equipment, the requirements for weight loss, stealth, impact resistance, high temperature resistance and other performance requirements are getting higher and higher. Traditional materials are becoming increasingly difficult to meet a number of requirements. Composite materials have become an important basis for the development of military equipment, and their application level has also become one of the advanced standards for measuring the development of weapons and equipment. Modern high-tech war requires weapons and equipment to have the characteristics of rapid response, high maneuverability, integrated penetration defense, and long-range precision strike, which has promoted the leap of weapons and equipment from structure to function. Composite materials have the characteristics of high specific strength, high specific modulus, high temperature resistance, corrosion resistance, fatigue resistance, integrated material structure and function, integrated design and manufacturing, and easy to form large components. They have been widely used in the fields of weight reduction, impact resistance, high intensity defense, high temperature resistance, stealth resistance, etc., promoting the lightweight, high performance, functionalization and intelligence of weapons and equipment, and have become one of the important material foundations for the development of high-tech weapons. At the same time, in recent years, composite material technology has continuously made breakthroughs, and the decline in costs has made composite material more widely used. Overall, composite technology and equipment development complement each other and promote each other, that is, the development of composite material preparation and application technology has promoted equipment upgrades, and the continuous development of equipment has also forced composite technology to continue to advance. As the design and processing capabilities of domestic and foreign composite materials gradually increase, the cost will further decline, and the application of composite materials in weapons and equipment will be further improved in the future.
The United States and Japan were the countries that started the preparation and application of composite materials earlier, with relatively mature technology and a higher proportion of applications in weapons and equipment and civil aviation. According to the document "Application of Composite Materials in the New Generation of Large Civil Aircraft" published in 2015, the proportion of composite materials used by the U.S. F-35 fighter is 35%; the large civilian passenger aircraft B787 and A350XWB respectively reach 50% and 52% of the structural weight; the new U.S. military transport aircraft ACCA builds the aircraft through integral molding, with the proportion of composite materials of the entire aircraft body as high as 65%, and the weight reduction of the entire aircraft can even reach more than 25%.
With the continuous development of domestic equipment and the gradual maturity of composite preparation technology, the proportion of composite materials application in equipment is also increasing, but there is still a gap between the overall level and abroad, and there is still a lot of room for improvement in the future. According to the "Development History and Prospects of Advanced Composite Materials on Military Fixed-wing Aircraft" published in 2014, the proportion of composite materials used in my country's fourth-generation aircraft accounts for about 20% of the entire machine components, while the proportion of composite materials used in foreign advanced fighter aircraft can reach 35%; my country's large ships have not yet used composite materials superstructures, and the United States has adopted composite materials superstructures in the first two DDG1000 destroyers, which has greatly improved the stealth capability of ships .
composite materials have gradually increased in application proportion on fighter jets, and they have been able to be used as main bearing structural parts
With the development of reinforcement materials, substrates and composite materials preparation technology, the usage of composite materials in military aircraft has gradually increased. According to the document "Application and Development of Advanced Composite Materials for Aircraft Structures" published in 2006, after 2000, the use of the world's advanced composite materials on aircraft ranged from 20% to 50% of the total structural weight. The application of composite materials in foreign military fighter jets has gone through four stages: "small force-bearing parts → secondary force-bearing parts → main force-bearing parts → landing gear application". From the initial stage, it can only be applied to components with less force, it has developed to now be able to be applied to main force-bearing structural parts and landing gears.
. In the first stage, it is mainly used on components with relatively small stress such as hatch doors, covers, rectifiers, flaps, ailerons, rudders, etc. In the early 1960s, glass fiber reinforced composite materials began to be used in fairings, flaps, ailerons, etc. in military aircraft. During this period, the mechanical properties of composite materials were relatively low, and the stress level of the manufactured aviation parts was correspondingly smaller, and the size of the parts was also smaller.
. In the second stage, composite materials began to be applied to secondary load-bearing structural parts such as vertical tail wings and horizontal tail wings of military aircraft. The proportion of composite materials can reach 5% in this stage. , such as the US F-14 fighter, applied boron fiber-reinforced epoxy resin composites to flat tails in 1971, becoming a milestone in the history of composite materials development. Since then, continuous carbon fiber reinforced composite materials have been applied to the tail wings of aircraft such as F-15, F-16, MiG-29, Phantom 2000, F/A-18, etc.Since the early 1970s to the present, all the tail-level components of foreign military aircraft have been made of composite materials. Generally, if the vertical tail and flat tail of a military aircraft are all made of composite materials, the weight of these parts can account for about 5% of the total structural weight.
. In the third stage, composite materials are gradually applied to the main bearing structures such as the wings and fuselage of military aircraft, and the proportion of composite materials is 20%~50%. The original American McDonald Aircraft Company was the first to develop the composite wings of the F/A-18 aircraft in 1976 and entered service in 1982, increasing the use of composite materials to 13%, becoming another important milestone in the history of composite materials application development. Since then, foreign military aircraft have followed suit. Almost all the wing-level components developed by military aircraft developed by countries around the world have used composite materials without exception, such as the United States' AV-8B, B-2, F/A-22, F/A-18E/F, F-35, France's "gust", Swedish JAS-39, Europe's "typhoon" jointly developed by Britain, Germany, Italy and the West, Russia's "golden eagle", etc. At present, the amount of composite materials used in the world's advanced military aircraft ranges from 20% to 50% of the weight of the entire aircraft's structure.
. Stage 4: The application of composite materials on landing gear. Since the application of landing gear is to replace steel parts rather than aluminum parts, the weight reduction space is further improved. Composite landing racks are more durable, lighter, more corrosion-resistant and have lower production costs than landing gears made of traditional metal materials. In addition, the production cycle of composite landing gears is shorter, usually only 2 to 3 months, while the delivery time of many traditional metal landing gears is as long as 2 years. At present, the composite landing gear rear pole of the US F-16 fighter has completed verification flight; the French Rafale fighter also uses carbon fiber composite on the landing gear.
Before my country's fourth-generation machine, the application scope of composite materials was limited to the secondary bearing structures such as tail wings and canards, and the usage accounted for less than 10%. The usage of composite materials in the fourth-generation machine has made a significant breakthrough, and the usage of composite materials reached about 20% of the structural parts of the entire machine. The design and research of composite materials in domestic military aircraft has not started late. Since the late 1960s and early 1970s, relevant scientific researchers from domestic related units have begun to apply advanced composite materials to domestic fighter jets, and have successively carried out research on the application of composite materials for the tail wing and front fuselage of the J-8 and a certain type of strong-5. Since then, composite materials have been used on newly designed military aircraft. For example, the J-10 fighter jets account for 6% and the J-11 fighter jets account for 9%, but generally no more than 10%. The newly developed fourth-generation fighter composite material usage has made a significant breakthrough, with composite material usage accounting for about 20% of the entire machine structural parts, and the target usage has been increased to 29%.
Helicopter body and blade use composite materials is relatively high
composite materials on helicopters have promoted the leap in helicopter technology. The amount of composite materials used in the body structure has now become one of the important indicators to measure the advanced level of the new generation of helicopter technology. Looking at the development process of modern helicopters, helicopters have experienced two major technological leaps. The first technological leap was the application of turboshaft engines in the 1960s, and the second technological leap was the application of composite materials in the 1970s. The application of composite rotor blades in helicopters not only greatly improves the life of the blades, but also achieves optimized blade design, significantly improving the aerodynamic performance of the rotor. Almost all third-generation helicopters developed in the 1970s use composite rotor blades. The fourth-generation helicopters developed since the 1980s also use composite materials in the fuselage structure, and the usage has accounted for 35% to 50% of the structural mass fraction. In recent years, all-composite helicopters have even appeared. The large-scale use of composite materials in rotor systems and fuselage structures has become the main technical characteristics of the third and fourth-generation helicopters.
In recent years, composite materials have been used more and more in foreign helicopters. Some models of composite materials account for more than 50% of the body structure weight ratio, and even fully composite materials helicopters (NH-90 helicopters) have been produced, and composite materials account for as much as 95% .Composite materials have the advantages of lightweight, high specific strength, high specific stiffness and strong designability. Using them in helicopter structures can effectively achieve structural weight reduction and improve flight performance, safety and reliability. Therefore, in recent decades, the proportion of composite materials in helicopters has become increasingly high. According to the document "Current Status and Development of Helicopter Composite Materials Application" published in 2016, the RAH-66 Koemanchi helicopter body uses a large number of carbon fiber/epoxy, aramid/epoxy and honeycomb core materials, accounting for 54% of the body's structural weight; the NH-90 helicopter composite material consumption accounts for as high as 95%, and a fully composite material body is used. Only the power chamber platform and its partition are made of metal parts, and the rest are all made of carbon fiber composite materials, aramid composite materials and NOMEX honeycomb core materials. The rotor system uses carbon fiber composite materials and glass fiber composite materials. Compared with the all-metal structure, the number of parts is reduced by 20%, the mass is reduced by 15%, and the production cost is reduced by 10%.
Advanced application of helicopter composite materials in my country, and currently, both under research and in-service helicopters in China use a large number of composite materials. The Z-9 helicopters developed in the 1980s have used a large number of composite materials, mainly used in structural components such as main blades, ducted large vertical tails, flat tails, side end plates, cockpit covers and other structural components. The rotor blades and tail rotors of the straight-11 type helicopter adopt a fully composite structure, and the hub star flexible parts and plywood are both composite structures. Z-10, Z-19 There are also large quantities of airframe frame structures, helicopter rotors, wing skins and helicopter tail components made of carbon fiber materials on armed helicopters. At present, both under research and in-service helicopters in China use a large number of composite materials, and the main application areas include beams, skins, pads, trailing edge strips, etc. in rotor blades, and under-floor components in the body structure, cabins, power cabin fairings, short wings, tail beam skins, wall panels, tail oblique beams, tail section fairings, instrument panels, and light shields.
UAV uses composite materials at a higher rate, generally higher than manned fighter
In order to reduce weight as much as possible, UAVs use composite materials in large quantities, and the usage is generally higher than manned fighter erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile erectile er drone has distinctive technical characteristics of low cost, light structure, high maneuver, large overload, long range and high stealth. These characteristics determine their urgent need for weight loss. The emergence of composite materials has enabled the weight loss requirements of drones to be realized. According to the document "The Application Trends of Advanced Composite Materials in Military UAVs" published in 2013, the use of composite materials on various UAVs is relatively large, generally higher than that of manned aircraft, generally between 60% and 80%, and some even use composite materials in the entire structure. The application and development of composite materials in drone bodies has gone through the development process of integrated forming such as the leading edge and trailing edge wall of the aircraft wing surface, to the operating surface or the trailing edge of the wing surface, as well as the main bearing structure, and then to the integrated forming of the wing surface box section and wing body fusion.
composite material has also been widely used in my country's multi-type drones. The stressed skeleton of the BZK-005 long-range unmanned reconnaissance aircraft jointly designed by Hafei and Beihang adopts a conventional aluminum alloy riveted structure, the skin and fairing are made of glass fiber, carbon fiber, paper honeycomb and other composite materials, and the wings are composed of fully composite materials. "Xianglong" UAV reconnaissance aircraft uses a large number of composite materials, the fuselage curve is continuous and smooth, and the dorsal fin of the tail of the fuselage is equipped with a composite engine bay, making its radar scattering cross-sectional area about 1m2, which has good stealth performance. "Winglong-1D" is China's new generation of improved multi-purpose drones, with fully composite materials in the fuselage structure.
civil aviation passenger aircraft application proportion continues to increase, and the proportion of domestic C919 application composite materials accounts for 12%
civil aircraft emphasizes both safety and economy, and there is also an urgent need for structural weight loss. The usage of composite materials is also constantly increasing, and the application ratio of structural materials can reach 50%. Boeing B787 aircraft (first flight in December 2009) has a composite material usage of 50%, mainly used in wings, fuselage, vertical tail, fuselage floor beams, rear pressure frames and other parts. It is the first large commercial passenger aircraft to use composite wings and fuselages.A350XWB (first flight in June 2013) is currently a passenger aircraft with the largest proportion of composite materials in the entire structure weight, and composite materials account for 53% of the body's weight.
The amount of composite materials used in domestic civil aircraft is far behind that of Boeing and Airbus. domestic main line passenger aircraft C919 advanced composite materials in its body structure reaches 12%. Its wing composition is mainly carbon fiber composite materials, supplemented by aluminum-lithium alloy and titanium alloy, and the rear fuselage and flat vertical tail use T800 grade carbon fiber composite materials. The flaps and radome use glass fiber composite materials, the hatch doors and cargo hold floors use aramid honeycomb materials, the aircraft engine uses carbon fiber composite materials and ceramic matrix composite materials, and the use of composite materials reduces C919 by more than 7%.
composites are mainly used in aerospace equipment to reduce weight and prevent heat
aerospace equipment such as missile , rockets, hypersonic aircraft, etc. generally have high flight speeds, high surface temperature during flight, and high requirements for heat protection. The missile flies very high in the atmosphere (close to or far exceeds the speed of sound). At this time, due to the aerodynamic heating of the missile, the surface skin and warhead temperature will rise rapidly. According to the calculation formula for standing point temperature, assuming that the ambient temperature of the missile is 220K, we have initially calculated the temperature of the missile skin at different flight speeds. It can be seen that when the missile's flight speed reaches 4~10 Mach , the surface temperature can reach 445~3173℃. With the increase of the Mach number, the surface temperature rises sharply. Ordinary aluminum alloys and even titanium alloys are difficult to meet the requirements. For example, the US improved supersonic sea sparrow missile can reach 371℃ in 8~10 seconds after launch. In this environment, the strength of the 2024 aluminum alloy will be reduced by 90%, which is difficult to meet the requirements. Therefore, for high-speed flight aerospace equipment, various types of ceramic materials and composite materials need to be used to achieve heat protection. For example, the US X-47B hypersonic aircraft uses carbon/ceramic composite materials to prevent heat, and the temperature resistance can reach 1700℃.
Aerospace equipment also has strict weight requirements. The use of advanced composite materials can achieve weight loss, which is significant for increasing range and improving accuracy. According to the document "Application of Advanced Polymer-based Structural Composites in Missiles and Aerospace", every 1kg reduction in the mass of strategic missile warheads and upper-level engines can increase the range of intercontinental missiles by 20km. In the early 1960s, the United States used fiberglass instead of ultra-high-strength steel to successfully wrap the "Polaris" subsea missile engine shell, which increased the missile range by 27%.
tactical and strategic missile
composites are usually used in tactical missiles in order to use bullet bodies, wings, tail wings, radons, air intakes and other positions. The early "War Axe" cruise missiles in the United States used more composite components, such as head cone, radon, tail wing, air intake, etc., but their performance was average. At that time, most of other tactical missiles were still mainly metal materials. Since the 1980s, composite materials have been used for solid engine shells and part of the shell skin of various tactical bombs. For example, the new generation of US air-surface cruise missile ACMI58-JASSM, in order to significantly reduce the cost and reduce the weight of the bomb body on the basis of the Tomahawk cruise missile, not only the wings, tail wings, and air intake ducts are made of composite materials, but all sections of the entire bomb body are made of carbon fiber composite materials, which reduces the weight of the entire bomb by 30% and reduces the cost by 50%. my country uses composite materials on subsonic shore ships and ship missile radomes, with epoxy composite materials as the skin and polyurethane foam as the core layer.
In the 1960s, composite materials were used in the United States' "Polaris" strategic missiles. Since then, the United States' "Military", "Sea God", "Trident-I", "Gnome", "Trident-II", and "MX" series missiles; France's M-4 and M-5 missiles; the former Soviet Union's SS-24 and SS-25 missiles all use composite materials. In addition to the missile itself, composite materials are also used in the launch cylinder, which can achieve significant weight loss. For example, the launch cylinder of the US MX missile is 22.4 meters long and 2.5 meters in diameter. Its mass exceeds 100 tons when using high-strength steel, while only 2 tons after using carbon fiber reinforced resin matrix composites. my country's strategic missile launcher also uses some carbon fiber composite barrel sections, which is 28% lighter than aluminum alloy components.
We believe that the application of composite materials in missiles will continue to grow in the future. With the improvement of performance and cost of advanced reinforcement materials and resin matrixes, advanced composite materials may increasingly replace traditional metal materials of missiles, thereby greatly reducing the weight of the weapon system and improving combat effectiveness.
Launch Vehicle
Launch Vehicle's main components of advanced composite materials are solid engine (solid booster and upper stage engine) shell, arrow body interstage section, arrow satellite bracket, payload bracket, and reusable world round-trip aircraft skin. In recent years, my country has widely used composite materials in various models of launch vehicles, especially the upper stage structure, which effectively reduces the quality of the upper stage structure and has a very obvious effect on improving the launch vehicle's launch payload ability. For example, the fourth stage engine of the "Trail Blazer-1" small launch vehicle uses a high-performance carbon fiber shell; the satellite interface bracket and payload bracket (front and rear end frames, ring frames, shell sections, spring brackets, tic toe beams) of the Long March Rocket (CZ-2C, CZ-2E, CZ-3A) use carbon fiber reinforced epoxy resin matrix composites.
Satellite
Currently, the main structural components of satellites (solar array, payload, body structure, truss) are generally used in high-performance composite materials. The use of composite materials in satellites has a very obvious effect on reducing mass. Generally speaking, every 1kg of satellite mass is reduced, the emission mass can be reduced by 100kg. Therefore, composite materials are widely used on satellites, especially high-mode carbon fibers. Among the nine Intelsat-7 satellites launched in 1993, advanced composite materials account for 50% of their structural mass. Since the mid-to-late 1980s, the use of composite structural parts in my country has increased rapidly, resulting in the continuous reduction of the quality of satellite structures.
Application of composite materials in the ship field
Composite materials are light in weight, high designability, and strong corrosion resistance. They are one of the best material choices for ship equipment in the future to pursue larger payloads, stronger comprehensive stealth capabilities, and lower full life expenses. composite materials are generally light in weight and high in strength. The specific strength is higher than traditional shipbuilding structural materials such as hull steel and aluminum alloys. They can effectively improve the stability, speed and carrying capacity of ships; they are easy to be made into streamlined and other complex shapes; they are better than traditional metal materials; they can reduce the generation of noise by enhancing the stability of internal components under damping vibration; they can reduce the reflection cross-section of radar to achieve stealth effect; they are non-magnetic and are not easily detected by torpedoes and mines; they can greatly reduce the thermal characteristics of the ship; they can change the matrix and reinforcement as needed to achieve specific goals. Due to these characteristics of composite materials, composite materials are made an ideal marine material.
Composite materials started late in the application of ships, but replacing some metal materials with composite materials has become the future development trend of ships. The application of composite materials on ships has also evolved from non-bearing structural parts to secondary bearing structural parts and main bearing structural parts. The use of composite materials in foreign naval ship superstructures began in the mid-1960s and was originally used to manufacture gunboat deck chambers on patrol gunboats. After the 1970s, the superstructure of mine hunting boats also began to use composite materials, such as the Rauma, the rapid patrol boat of the Royal Finnish Navy. After the 1990s, composite materials began to be used in fully enclosed mast/sensor systems of ships. As the application effect of composite materials has gradually been recognized by various naval powers, the application of composite materials on ships has shown a trend of evolution from non-bearing structural parts to secondary and primary bearing structural parts, and from individual experimental applications to comprehensive promotion and application. At present, new foreign destroyers such as the US DDG 51 destroyer, DDG 1000 destroyer, and British Type 45 destroyer are typical platforms for the application of advanced resin-based composite materials.Some ships are replacing traditional metallic components with composite structural parts, including small and medium-sized surface ship hulls; large surface ship superstructures, cabin walls, propellers, propulsion shafts and rudders; internal equipment and parts of surface ships, such as heat exchangers, equipment bases, valves, pumps, pipelines, guardrails; submarine non-pressure-resistant shells, sonar shrouds, rudders, horizontal wings, propulsion systems, bases, periscopes, torpedo launch tubes, etc.
composite materials are also widely used in the civil ship field at home and abroad. composite material is the most suitable structural material for small and medium-sized boats, especially high-speed boats and high-performance boats. It has been widely used in domestic and foreign civil ship fields, such as yachts, fishing boats, lifeboats, transportation boats and high-performance boats.
Compared with foreign countries, the application scope and scale of marine composite materials in my country are still relatively small. In the mid-1970s, my country developed a minesweeping test boat with a total length of nearly 39 meters. Since the 1990s, with the development of technology and the introduction of technology, my country has used composite materials to produce a large number of yachts, sailboats, rescue boats, as well as patrol boats, law enforcement boats, anti-smuggling boats and other paramilitary boats with higher speeds such as public security, armed police, maritime surveillance, customs, etc., but so far, no high-tech composite military ship has been designed and built. In terms of composite ship components, my country successfully developed composite sonar shrouds in the late 1960s and applied them to submarines. It has developed to form a relatively mature application. In the late 1980s, composite radar radome and mine shell were developed and put into use. In the 1990s, composite masts were successfully developed for large surface ships. Application of
composite materials in army equipment
composite materials in tanks and armored vehicles mainly include armor and operation systems, with the purpose of reducing weight and improving anti-strike performance. The application of composite materials in tank and armored vehicles began in the 1970s. Soviet T-64A was the first main battle tank to use composite armor. Nowadays, composite armor developed by glass fiber, Kevra, carbon fiber, etc. as reinforcement materials, compared with metal armor of the same protection level, the use of composite materials can increase the comprehensive performance of the vehicle body and turret structure by 30%~50%, and reduce the weight by 40%~45%. In terms of operation systems, such as tank tracks, load bearing wheels, pulleys, torque shafts, etc., the composite material fully exerts the weight reduction effect. For example, the ceramic reinforced aluminum-based composite tracks used by the US military's 25t light tank armored combat vehicle reduce the total weight of the tank by 1 ton; the load-bearing wheels of glass fiber/epoxy composites used in the M113 tank combat vehicle not only reduce weight by 30% compared to traditional materials, but also greatly reduce the damage caused by mine explosions. The M60 tank uses carbon fiber/epoxy resin composites to replace steel torque shafts to reduce weight by more than 65%. Tank engines use piston heads, piston connecting rods, speed control gears, propulsion rods and other metal components, and are made of resin-based composite materials, which will reduce weight by more than 30% compared to traditional metal components.
composite material is mainly used on gun barrels, with the purpose of reducing weight to improve mobility. Foreign countries have made high-strength fiber resin-based composite materials into artillery barrels, artillery barrel thermal sheath, slings, traction rods and other components, which can greatly reduce the weight of the artillery and improve its maneuverability. Taking the composite material for artillery gun tubes as an example, the United States used graphite/epoxy composite materials to prepare the lengthened body tube of the rotary barrel to replace the traditional metal lengthened body tubes, which not only improved the shooting accuracy of the artillery, but also achieved a weight loss of 37%.
composites are widely used in light weapons, and their main purpose is to lose weight. In the 1970s and 1980s, resin-based composite materials gradually replaced traditional metal materials and were used to prepare guns' magazines, sleeves, transmitter bases, sights, piercing holders, triggers, continuous iron barriers and other component ports. , such as the AR-24 assault rifle in the Soviet Union in the 1970s, uses glass fiber reinforced phenolic composite materials to make magazines, which is 28.5% lighter than metal magazines; the US M60 7.62mm universal machine gun uses resin-based composite material cables, which are 30% lighter than metal cables.Since then, in order to further reduce weight, improve precision and durability, composite barrels made of carbon fiber/epoxy composite materials have been released. For example, Germany uses the winding molding method to wrap metal wires on ceramic inner tubes to enhance epoxy resin molding machine gun barrels.
3. Carbon fiber: strong military demand, great growth potential in the future
"After the age of 80, I could have been less involved, but I was unwilling to do it and still wanted to grab carbon fiber. If China's carbon fiber cannot go up, national defense security will be unsure, and I will die with my eyes open" - Academician Shi Changxu (early 2000)
is divided into three types according to the raw materials, among which PAN-based carbon fiber occupies the mainstream
Carbon fiber has excellent performance and is widely used in the defense fields such as aerospace. carbon fiber is a high-strength, high-modulus fiber material with a carbon content of more than 95%. It is a microcrystalline graphite material obtained by stacking sheet-shaped graphite microcrystals along the axial direction of the fiber and being carbonized and graphitized. Carbon fiber composite materials are widely used in the national defense field for their advantages of lightweight, high specific strength, high specific stiffness, fatigue resistance, corrosion resistance, and easy to form a large area, as well as their unique designability, and play a key role in the lightweight, high performance, and long life of weapons and equipment. The amount of them has also become one of the symbols of the advanced nature of weapons and equipment.
Carbon fiber is mainly divided into three categories: viscose-based, asphalt-based and polyacrylonitrile-based (PAN) carbon fiber according to the different raw materials, among which PAN-based carbon fibers are the mainstream. Carbon fibers with high mechanical properties must be graphitized by high temperature stretching and high carbonization efficiency, low technical difficulty, complex equipment, high cost, and low output. The products are mainly used for ablation-resistant materials and heat insulation materials; carbon fibers are made from asphalt, with rich raw materials and high carbonization yields, but due to complex raw material preparation and low product performance, they have not been developed on a large scale; high performance carbon fibers made from polyacrylonitrile fiber raw silk have relatively simple production process, and the product has excellent mechanical properties and wide uses. Therefore, since its inception in the 1960s, it has made great progress, and its output accounts for more than 90% of the total global carbon fiber, becoming the mainstream of today's carbon fiber industry production.
PAN-based carbon fiber
PAN-based carbon fiber preparation process mainly includes four stages: PAN raw silk preparation, preoxidation, carbonization, and post-treatment.
. Preparation of raw silk : The preparation of PAN raw silk is to polymerize polyacrylonitrile monomer into a spinning raw liquid, and then spin it into molding. The raw silk preparation process is the core process of PAN-based carbon fiber. The quality of PAN raw silk directly determines the quality, output and production cost of the final carbon fiber product. The spinning process of raw silk can be divided into four types: wet method, dry method, melt method and dry spray wet spinning (dry wet method). Among them, wet spinning is the most widely used process at present, and wet method is the most advanced spinning process at present. It can have the advantages of both dry method and wet method. The spun fibers have a high density, a smooth surface without grooves, which can produce high-performance carbon fibers, and can effectively improve the production efficiency of fibers and reduce manufacturing costs.
. Pre-oxidation: pre-oxidation, also known as thermal stabilization, is the longest process in the preparation of carbon fibers, generally 60~120min. The pre-oxidation reaction is generally carried out within the temperature range of 200~300℃. The transformation of the fiber structure during the pre-oxidation process largely determines the structure and performance of the final carbon fiber. If the temperature is too low, the pre-oxidation reaction is slow or insufficient, it takes too long and the production efficiency is low; if the temperature is too high, it can easily lead to excessive oxidation, fuses and even burning wires.
. Carbonization: Under the protection of inert gas, pre-oxidized fibers are first passed through a low-temperature carbonization furnace. Non-carbon elements such as nitrogen, hydrogen, and oxygen react and release them in the furnace. Carbonization is generally achieved by two parts: low-temperature carbonization and high-temperature carbonization. The temperature in the low-temperature zone is generally between 300 and 600℃, and the temperature in the high-temperature zone is generally between 600 and 1600℃. The conditions of the carbonization process have a direct impact on the final carbon fiber strength.
. Post-treatment : In order to obtain carbon fibers with a higher modulus, the carbon fibers produced after carbonization are also required to undergo high-temperature heat treatment, that is, graphitization of carbon fibers.Graphitization can improve the tensile strength and tensile modulus of carbon fibers.
Asphalt-based carbon fiber
Asphalt-based carbon fiber is an indispensable engineering material in the aerospace industry. The research and development of asphalt-based carbon fiber began in the late 1950s, was successfully developed by Gunma University in Japan in the early 1960s, and industrialized production was achieved at the Japanese Wuyu Chemical Industry Company in the late 1960s. Although the compressive strength and processing properties of asphalt-based carbon fiber are inferior to those of PAN-based carbon fiber, it has excellent heat transfer performance, conductivity, high modulus and extremely low thermal expansion coefficient, making it play a unique role in the military and aerospace fields. The preparation of asphalt-based carbon fiber generally includes processes such as raw material modulation, polycondensation reaction, spinning and carbonization. The key steps in synthesis of carbon fibers are the polycondensation reaction of the precursor and the high-temperature carbonization reaction of the carbon fibers.
Currently, the companies that can produce asphalt-based carbon fiber on a large scale are mainly Japanese and American companies, and the production and demand for general-grade asphalt-based carbon fibers are balanced. The main manufacturers of universal grade bituminous carbon fibers are Japanese Wuyu Chemical Industry Company. The main manufacturers of high-performance bituminous carbon fibers are Japanese Mitsubishi Chemical Company, Japanese Graphite Fiber Company and American BP Company. Since the early 1970s, the Shanghai Coking Plant and the Shanxi Institute of Coal Chemical of the Chinese Academy of Sciences have conducted research and achieved certain research results. According to the "Carbon Fiber Composite" document in January 2017, the world's demand for asphalt-based carbon fiber is about 2,000 tons, and the output is about 2,000 tons, and the international market is basically balanced; the domestic general-grade asphalt-based carbon fiber production capacity is about 100 tons, and the production and demand are also basically balanced.
viscose-based carbon fiber
viscose-based carbon fiber has high production costs, and the overall performance indicators are worse than those of PAN-based carbon fiber, so the application is limited. Viscose-based carbon fiber is a fiber material that uses viscose fiber as raw material. After low-temperature heat treatment, it is subjected to high-temperature heat treatment above 800°C in a non-oxidizing atmosphere to finally produce a fiber material with carbon as the main component. The process flow of producing viscose-based carbon fiber is long, the process conditions are harsh, the carbonization yield is low, it is not suitable for mass production, and the cost is high. At the same time, the overall performance indicators of viscose-based carbon fiber are worse than those of PAN-based carbon fiber, so its application is limited. The unique properties of
viscose-based carbon fiber make it applicable in fields such as national defense. Although the output is low, it is difficult to completely eliminate it. The unique properties of viscose-based carbon fiber are mainly reflected in: low density, about 15% less than ordinary PAN-based and asphalt-based carbon fibers, and the produced composite materials are easier to achieve lightweight; they are large-elong carbon fibers, with good toughness and easy to deep processing; they are converted from natural cellulose, and have good biocompatibility; they have low alkali and alkaline earth metal content, good oxidation and thermal stability, and ablation resistance. Although the process of viscose-based carbon fiber is harsh and the yield is low, these unique properties make it suitable for application in thermal insulation scenarios and medical biological materials, so viscose-based carbon fiber is difficult to completely eliminate. For example, both the United States and Russia use viscose-based carbon fiber as a reinforcement material for composite materials for large-area heat-proof materials for intercontinental strategic missile warheads. Currently, Russia ranks first in the world in the development, research and application of viscose-based carbon fibers. United Carbonization Company and Hitco also have certain strength in viscose-based carbon fiber production.
PAN Basic carbon fibers are divided into three categories according to their mechanical properties. They each focus on the application in the defense field. According to their mechanical properties, carbon fibers can be divided into high-strength carbon fibers, high-model carbon fibers and high-strength and high-model carbon fibers. Take Dongli's products as an example. It mainly produces three series of carbon fibers, namely high-strength T series, high-model M series, and MJ series with both high-strength and high-model, among which high-strength and high-model models include T300, T600, T700, T800 and T1000; high-model carbon fibers are mainly M30, M40 and M46, and the high-model carbon fibers circulated in the market are mainly M40; high-strength and high-model carbon fibers are mainly M46J, M50J, M55J, M60J and M65J.
Different types of carbon fibers are used in the defense field, but the application focus is different. High-strength type is mainly used in the aviation field, and high-model type is mainly used in the aerospace field.'s first generation carbon fiber is the standard modulus carbon fiber, represented by Toray's T300 and Hearth's AS4 carbon fiber, and is mainly used for aviation sub-capacity bearing components. For example, the T300 is mainly used for Boeing 737 and other models. The AS4 is used in the flat tail and other parts of the early F-14 fighter jets. The second generation of high-strength carbon fiber is represented by Toray's T700, T800, T000 and Herst's IM7, IM8, and IM9 series, and is mainly used in aviation main bearing components. For example, the T800 is widely used in the main bearing structure of aircraft wing fuselages such as the A350 and Boeing 787. The IM7 is widely used in the United States' "Trident" II submarine-launched missiles and F-22 and F-35 fighters. However, due to the low modulus and the high brittleness of carbon fibers in the second generation, it is easy to cause fatigue damage to composite structural components, limiting the improvement of weapon equipment performance. Therefore, the United States, Japan and other countries are studying the third generation of high-strength carbon fibers. Among them, Toray has developed the third generation of carbon fiber T1100G carbon fiber, which is entering the industrialization stage. In the aerospace field, satellite structure design mainly solves the rigidity problem when meeting the strength conditions. It requires carbon fiber to have a certain strength and also have high modulus or ultra-high modulus. Therefore, high-model carbon fiber is mainly used in the aerospace field. High-strength and high-model carbon fiber can maintain high modulus, combine high tensile strength, compression strength and elongation of break, and can be used as a main bearing structural component in both aerospace and aerospace.
Japan-US PAN-based carbon fiber technology and industrialization are in a leading position
Japan Toray is a global carbon fiber industry leader. 961 Dr. Akio Kondo from the Osaka Industrial Research Institute of Japan successfully developed PAN-based carbon fiber using Oren from DuPont as raw materials. In 1967, Japan Toray Company developed a copolymer polyacrylonitrile raw wire suitable for the manufacture of carbon fiber. After that, it built a first-generation carbon fiber test production line with an annual output of 12 tons in 1971. It was then expanded and named T300. In 1984, Toray successfully developed T800H carbon fiber (second-generation carbon fiber), with its strength being nearly 56% higher than T300 carbon fiber and its modulus being nearly 28% higher than T300 carbon fiber. In 1986, T1000G carbon fiber was successfully developed, with the same modulus as T800H carbon fiber and its strength was 16% higher than T800H carbon fiber. In March 2014, Toray successfully developed T1100G carbon fiber (third generation carbon fiber) with high strength and high modulus. Its strength is 20% higher than that of T800H carbon fiber and 10% higher modulus. In June 2017, the strength was updated from 6600MPa to 7000Mpa, and is currently undergoing industrialization. Toray's high-strength carbon fiber has achieved the cross-generation development of three generations of carbon fiber represented by T300, T800 and T1100G. In terms of high-mode carbon fiber, Toray has also developed a variety of high-mode fibers and high-strength high-mode fibers.
Toray previously mainly produces high-performance small tow carbon fiber, and through the acquisition of ZOLTEK company, it has entered the low-cost large tow carbon fiber segment industry. In 2015, Toray acquired ZOLTEK (ZolTEK) in the United States, which is the first company in the world to develop and produce cheap and high-performance large tow carbon fibers. Large tow carbon fiber is priced lower than small tow carbon fiber. For example, 3K carbon fiber commonly used in aircraft structural parts is priced at around US$50/kg internationally, while ZOLTEK's 48K large tow carbon fiber is priced at only US$12-15/kg. In 2018, ZOLTEK announced that it would expand its production capacity in Hungary and Mexico, from 10,000 tons/year to 15,000 tons/year, and from 5,000 tons/year to 10,000 tons/year. Once the production expansion plan is completed, ZOLTEK's total production capacity of large tow carbon fiber will be increased to 25,000 tons/year.
In addition to Japan Toray Company, companies such as Tobon Rayon and Mitsubishi Rayon have developed their own technology and carried out industrial production of carbon fiber. Currently, Japan has a complete rayon-based, PAN-based, asphalt-based and mesophase asphalt carbon fiber industries, occupying the commanding heights of various sub-technology and controlling the high-end product market.
The industrialization of PAN-based carbon fiber in the United States lags behind Japan, but still has strong strength. The United States has technologies, products and production capacity that can guarantee military use, but its cost-effectiveness advantages are not as good as Toray. HEXEL (Hexel) is the largest carbon fiber research and production company in the United States, and its products have been widely used in military aircraft.The carbon fiber produced by HEXEL company has three series and nine grades, namely: AS4C, AS4 and AS4D of the AS series; IM4, IM6, IM7, IM8 and IM9 of the IM series, and UHM series high-mode UHM graphite fibers. Among them, the tensile strength of the AS series carbon fiber is 3860~4207MPa, which is higher than that of the T300 of Japan Toray Company and is similar to T300J or T600S; the tensile strength of the IM series carbon fiber is 4138~6343MPa, which is equivalent to the T600S, T700S, T800H and T1000G of Toray Company. The carbon fiber produced by HEXEL has been widely used in A400M transport aircraft, RAH-66 Comanche helicopters, F-22 fighter jets, F-35C fighter jets and intercontinental missiles. Among them, the F-22 fighter jet uses IM7 fibers to be used in main bearing components such as wings and fuselages, and the proportion of composite materials accounts for 24.2%.
The carbon fiber market has a high industry concentration, and the production capacity of the three Japanese companies accounts for nearly half of the global total production capacity. According to the statistics of the "2017 Global Carbon Fiber Composite Materials Market Report", in 2017, the global carbon fiber theoretical production capacity was 147,100 tons, of which the total production capacity of three Japanese companies was 70,200 tons, accounting for 47.72%, and it has an absolute leading advantage. The theoretical production capacity of mainland China in 2017 was 26,000 tons.
my country's PAN-based carbon fiber research and development has not started late, but there is currently a big gap with foreign countries
my country's carbon fiber research and development has not started late, but it has been hovering for a long time. The research and development of domestic PAN-based carbon fiber technology began in the 1960s, but due to weak process foundation and backward equipment technology, the prepared carbon fibers have low quality and poor performance stability. The domestic technology has been hovering at a low level for a long time. Domestic carbon fibers in this stage cannot be used as reinforcement of structural composite materials, and are mainly used to prepare functional composite materials. Starting from 1996, Beijing University of Chemical Technology achieved a breakthrough in the preparation of organic solvent system for high-strength carbon fiber silk threads with circular cross-sections. China Petroleum and Jilin Petrochemical Company started engineering technology research based on this, and the domestic PAN-based carbon fiber preparation technology was successfully transformed. Under the guidance of the "one-stop" project, domestic carbon fiber technology has developed rapidly, and Weihai has expanded to be the first to realize the industrialization of high-strength carbon fibers. High-strength medium-mode and high-strength high-mode carbon fibers have also been successfully developed. In 2002, with the strong promotion of senior experts in the materials industry represented by Mr. Shi Changxu, 863 plans to establish a special research project on carbon fiber technology, and the Natural Science Foundation also supports the development of basic research related to carbon fiber. In 2005, the country implemented a "one-stop" management model for carbon fiber preparation and application. Under the guidance of Aerospace 703 Institute and Aviation Industry 601 Institute, domestic carbon fiber preparation and application technology developed efficiently and rapidly, solving the "existence or not" problem of domestic carbon fiber materials for major national defense equipment, and initially achieving independent guarantees of key materials. In 2006, Weihai Expansion began to build China's first thousand-ton carbon fiber production line, and was completed and put into production in 2009. Since then, a variety of models of carbon fiber have been developed. At present, China has been able to produce T300, T700, and T800 grade carbon fibers on a large scale, with domestic substitution capabilities, and has successfully developed T1000 and T1100 high-strength medium-mode carbon fibers and M55J and M60J high-strength high-mode carbon fibers.
…
Carbon fiber reinforced composite material is widely used in the national defense field
Carbon fiber reinforced resin matrix composite material refers to a composite material composed of organic synthetic resin as the matrix and high-performance carbon fiber as the filler. It has the characteristics of lightweight, high-strength, high temperature resistance, corrosion resistance, and excellent thermodynamic performance. It can meet the requirements of aerospace structural parts and has been widely used in satellites, rockets, military aircraft, and civil aircraft.
Aerospace field, there are applications on various foreign models, and the proportion of applications is getting higher and higher. China has also obtained applications on multiple models. Currently, the carbon fiber used in military aircraft is mainly T300 and T700 tow carbon fiber. The application of carbon fiber reinforced resin-based composite materials can reduce the weight of the aircraft, helping to improve the maneuverability of the aircraft and combat radius. It is increasingly used in combat aircraft, bombers, helicopters and drones. For example, F-16 fighters use carbon fiber/epoxy resin composite materials in structures such as intake incline plates, flat tails and vertical tails, and carbon fiber/bimaleamide composite materials are used in skins. In addition, although ordinary carbon fibers do not have wave absorption function, the composite materials with special-shaped cross-section carbon fiber and special-shaped structures have wave absorption capabilities. In addition, the absorbing coating can be used to create stealth structural materials. For example, the US B-2 stealth bomber and F-22 stealth fighter both use carbon fiber reinforced resin-based composites. According to the book "Carbon Fiber Composite Materials" published in 2017: With the improvement of the performance of domestic advanced resin-based composite materials and the continuous maturity of manufacturing technology, domestic carbon fiber reinforced resin-based composite materials have also been used in helicopters, fighter jets and large aircraft.
In the aerospace field, carbon fiber reinforced resin-based composites have been used in missile engine housing, missile missile body, rocket engine housing, satellite antenna and body structure. high-strength medium-mode carbon fiber composite materials have been widely used in intercontinental missiles first, second and third-stage engine bodies and new generation medium-range strategic missile engine bodies. For example, the third-stage engine combustion chamber shell and engine shell of the US "Gnome" small-stage missiles have been made of carbon fiber epoxy resin. The small kinetic energy missiles developed by the US Army have also begun to use carbon fiber/epoxy resin composite materials. According to the book "Carbon Fiber Composite Materials", China also uses carbon fiber composite materials as heat-proof materials such as engine nozzles and fairings in various strategic and tactical missiles.
Carbon fiber reinforced carbon matrix composite material is mainly used in aircraft brake discs and aerospace ablation-resistant materials
Carbon/carbon composite material is a carbon fiber reinforced carbon matrix composite material. It has a series of excellent properties such as low density, high specific modulus and specific strength, good high temperature performance, low thermal expansion coefficient, high temperature resistance, thermal shock resistance, corrosion resistance, and good friction and wear performance. It has been widely used in various fields such as aviation, aerospace, nuclear energy, chemical industry, and machinery, among which aviation braking is the most used.
In the aviation field, it is mainly used as a brake material for aircraft brake discs, replacing traditional powder metallurgical brake discs. The early aircraft brake pads used alloy discs, and the service life of carbon/carbon composite materials was 3 to 4 times higher than that of powder alloy discs, while the density was only 1/3 of the alloy. The friction coefficient and mechanical properties were stable at high temperatures and were easy to maintain. They were widely used in foreign military and civil aircraft. At present, more than 40 types of civil aircraft and more than 20 military aircraft used carbon brake discs, such as Boeing 747/757/767/777/787 in civil aircraft, Airbus A300/310/318/319/320/340 in military aircraft, as well as American F-series fighters and Phantom fighters in military aircraft, all use carbon/carbon composite brake material brake devices.
In the aerospace field, it is mainly used as ablation-resistant material in rocket engine nozzles and throat linings. carbon/carbon composite materials have been used in the aerospace field mainly as ablation-resistant material, and have been successfully used in the manufacturing of components such as the wing front edge, nose cone, cargo door, solid rocket engine tail nozzle and throat lining of space shuttles. For example, the United States successfully applied carbon/carbon composite components on the upper engine of the DeltaIII launch vehicle RL10B-2; all three stages of the US MX intercontinental missile, one and two stages of the Trident missile, and the third stages of the US Scout missile, etc., all used carbon/carbon composite materials as engine throat linings. According to the 2017 book "Carbon Fiber Composite Materials" report: my country has applied carbon/carbon composite throat linings to solid rocket engines.
Carbon fiber reinforcement has many types of other matrix composite materials, and some have obtained applications in the field of national defense
Carbon fiber can also be compounded with various other substrates, such as ceramic substrates, metal substrates, rubber substrates, etc., with more types, among which some materials have been applied in the field of national defense.
carbon fiber reinforced ceramic matrix composite material has excellent high temperature mechanical properties and thermal properties. It can maintain strength, modulus and other mechanical properties without degradation in an inert environment. It has better oxidation resistance and ablation resistance than carbon carbon composite material, and has a wide application temperature and life range. It has been used in aircraft engines, gas turbines, high-speed brake discs and space aircraft. For example, the C/SiC composite has been used as a nose cone and its accessories on the X-38 aerospace vehicle of NASA in the United States, and has been successfully tested; the European Arian-4 third-stage liquid hydrogen/liquid oxygen thrust chamber nozzle uses C/SiC; France uses C/SiC composite to the nozzle flap and outer flap of the M88 engine of the Furious Wind Fighter.
carbon fiber reinforced metal matrix composite materials usually choose aluminum, magnesium, nickel, titanium and their alloys as matrix materials. The material properties depend on the characteristics, content and distribution of the selected components. They usually have high specific strength, high specific modulus, good electrical and thermal conductivity, small thermal expansion coefficient, good dimensional stability, good wear resistance, good fracture toughness and fatigue resistance, etc., and have also been used in the national defense field. For example, carbon fiber reinforced aluminum-based composites act as large antenna support rods in NASA space telescopes.
military demand for carbon fiber is strong, with great growth potential in the future
military aircraft at the turning point of mass production. The proportion of new generation of military aircraft composite materials has increased significantly, and the demand for carbon fiber is expected to increase significantly. According to World AirForce 2018 data, the United States has a total of 13,407 military aircraft, of which the fighter aircraft is a combination of third-generation + fourth-generation; while China has a total of 3,036 military aircraft, of which the fighter aircraft is about 23% of that of the United States, of which the fighter aircraft is a combination of second-generation aircraft + third-generation aircraft + a very small number of fourth-generation aircraft. Compared with the United States, there is a big gap in quality and quantity of China's military aircraft, and it faces a relatively urgent need for renewal. Moreover, the use of composite materials in my country's new generation military aircraft has increased significantly. The use of composite materials in the fourth generation machine accounts for 20% of the weight of structural parts, and the third generation machine is only 10%. We believe that the production of new models will drive a significant increase in the demand for carbon fiber.
There is a large demand for land, sea, air and space missiles, and the demand for carbon fiber in the aerospace field is expected to continue to rise. Rocket Force is the core force of my country's strategic deterrence and the strategic support for its status as a major power. It is an important cornerstone for safeguarding national security. Its equipment construction has always attracted much attention. In the parade of victory in the War of Resistance Against Japan and the parade of the 90th anniversary of the founding of the Army, the Rocket Force's equipment appeared as the finale. The intensive equipment display also highlighted the maturity of my country's Rocket Force's equipment technology and began to enter active service on a large scale. In accordance with the requirements of "training in combat mode and fighting in training", the Rocket Force has carried out regular military readiness pulling and combat process inspection drills in recent years, organized more than 40 major training tasks, and joined forces with the theater and other services to carry out more than 30 assault offensive and defense, joint operations, and launched hundreds of missiles. At present, all missile brigades have organized red and blue confrontation drills and have independent launch capabilities. The troops responsible for combat readiness duty are at high alert at all times, and the launch unit missiles are on the rack and are ready to be launched at any time. On the afternoon of April 26, 2018, at the regular press conference of the Ministry of National Defense, Colonel Wu Qian, director of the Ministry of National Defense News Bureau and spokesperson of the Ministry of National Defense, claimed that the People's Liberation Army's rocket forces had been equipped with Dongfeng-26 missiles. After trial installation and combat inspection, this type of missile meets the conditions for a complete equipment force. After being equipped, it has officially entered the Rocket Force combat sequence. We believe that high-intensity training consumption and batch installation of new equipment for troops, military aerospace defense equipment has entered a period of industry growth, which is expected to increase the demand for military carbon fiber.
The proportion of composite materials used in ship equipment is relatively low, and the increase in the proportion of composite materials in the future is expected to increase the demand for carbon fiber. The amount of composite materials used by foreign ships is relatively high. For example, the United States has used a large number of composite materials on the superstructure of large destroyers (DDG1000), which greatly reduces the radar reflection cross-sectional area of the ship and improves the ship's stealth ability.At present, the amount of composite materials used by ships in my country is still relatively low. Superstructures are mainly metal parts. In the future, with the development of composite technology and the strengthening of equipment design capabilities, it is expected to increase the proportion of composite materials application on new ships, thereby increasing the demand for carbon fiber and its composite materials.
4. Silicon carbide fiber: break the blockade and achieve mass production, and is expected to open up a vast downstream space
Silicon carbide fiber can be divided into three generations according to its temperature resistance
Aerospace and the development of cutting-edge weapons has put forward new requirements for high-temperature structural materials. New aerospace vehicles and cutting-edge weapons Thermal end components require the material to have excellent specific strength, specific modulus, impact resistance and high temperature resistance in extreme environments. Metal and alloy materials are no longer able to meet the new requirements. Advanced ceramic matrix composite materials (CMC) have excellent properties such as high strength and lightweight, impact-resistant, corrosion-resistant, and high temperature-resistant, which can meet the use requirements of new equipment. CMC requires reinforced fibers to be resistant to high temperatures, oxidation, creep and corrosion.
Silicon carbide fiber is an ideal reinforced fiber material for high-performance composites. Common composite reinforced fibers in include organic fibers, glass fibers, carbon fibers, oxide ceramic fibers and non-oxide ceramic fibers represented by silicon carbide. Organic fibers cannot be used in high-performance CMC because their heat resistance temperature does not exceed 500℃, and ordinary glass fibers cannot be used in high-performance CMC because their melting point or softening point is lower than 700℃. Although carbon fibers can have temperature resistance up to 2800℃ in emotional atmosphere, they will be severely degraded when they are higher than 450℃ in oxidation atmosphere. Poor oxidation resistance greatly limits its application in oxidation environment; the heat resistance temperature of oxide ceramic fibers such as alumina, zirconia and basalt does not exceed 1200℃, and their high density and high thermal expansion coefficient limits their application; SiC fibers, as the most mature and commercial non-oxide ceramic fibers, have excellent properties such as high temperature resistance, oxidation resistance, high tensile strength, good creep resistance, and good compatibility with ceramic matrix. At the same time, SiC fibers The fiber combines structure, heat protection, wave absorption and other functions, and is an ideal high-performance composite reinforced fiber.
SiC fibers and their products have excellent performance and are key strategic materials. Foreign countries have long implemented strict technical blockades in China. Silicon carbide (SiC) fiber is an inorganic fiber with a β-silicon carbide structure made from spinning and pyrolyzed using organic silicon compounds as raw materials. It is divided into morphologically: whiskers and continuous silicon carbide fibers. Silicon carbide fibers have excellent mechanical properties, oxidation resistance, high temperature stability, electrical properties adjustability, and good physical and chemical compatibility with metal and ceramic substrates. It has a wide application prospect in the fields of aviation, aerospace, weapons, ships and nuclear industries, and is one of the key strategic materials for the development of high-tech weapons and equipment. Due to the important strategic significance and military sensitivity of SiC fibers, the United States, Japan and other countries have invested huge amounts of money from strategic heights to research and develop high-temperature resistant SiC fibers and their composite materials. SiC fibers have always been a product embargoed by foreign countries to my country.
SiC fiber has been developed for three generations, among which the third generation of silicon carbide fiber has the best temperature resistance. can be divided into three generations according to the thermal stability of SiC fibers. The first generation of silicon carbide fibers are high-oxygen and high-carbon SiC fibers, with an oxygen content of more than 10% (oxygen is introduced by the oxidative crosslinking of the original wire), and a free carbon content of more than 15%. A chemical reaction will occur inside the fibers above 1000℃ to generate SiO2 and gas-phase CO, which will cause hole damage to the fibers and seriously reduce the mechanical properties. Therefore, its operating temperature is generally not higher than 1000℃ in an oxygen environment; the second generation is low-oxygen (about 0.5%) and high-carbon (about 20% free carbon) content SiC fibers. Since the original wire is crosslinked with an oxygen-free electron beam, the oxygen content is significantly reduced. The use temperature of this fiber is increased to above 1200℃, but the excess carbon reduces the high-temperature oxidation resistance and creep properties of the fibers; the third generation is near stoichiometric ratio SiC The fiber has only a small amount of free carbon and trace oxygen, with an oxygen content of about 0.2%, and a C/Si ratio of about 1.05-1.08. A small amount of carbon excess is to ensure that the fiber is not rich in silicon and avoid seriously affecting its high-temperature performance. Third-generation silicon carbide fiber has excellent antioxidant properties and creep resistance, and the use temperature can reach 1600℃, which significantly broadens its application in the field of aerospace thermal components.
pioneer conversion method is currently the main method for industrial preparation of SiC fibers
pioneer conversion method is currently a relatively mature method and has achieved industrial production. It is the main method for industrial preparation of SiC fibers at home and abroad. The preparation methods of silicon carbide fibers mainly include pioneer conversion method, chemical vapor deposition method (CVD), micro powder sintering method (PS), activated carbon fiber carbon thermal reduction method (CR, also known as chemical vapor phase reaction method), etc. Among them, SiC fibers prepared by CVD method have high purity, high strength and high modulus, but high preparation cost and low production efficiency, making it difficult to achieve large-scale production, and the diameter is coarse and difficult to weave, which is not conducive to the preparation of complex composite components; SiC fibers prepared by PS method have good high-temperature creep resistance, but the fiber strength is low and the diameter is coarse. Carborundum, the United States, tried to produce this method, but has stopped production; the CR method has simple process and low cost, but the strength and modulus of the fiber are not high, and the braidability is poor, which is not conducive to industrial application; ceramic fibers produced by pioneer conversion method have good mechanical properties and fine diameters, which are suitable for industrial mass production, and correspondingly reduce the manufacturing cost (the cost is about 1/10 of the CVD method), and the performance improvement and potential improvement It has great strength and has become an ideal method for preparing high-performance fibers. Therefore, currently, Nippon Carbon, Ube Industries, DowCorning, and Bayer in the United States all use pioneer conversion method as the manufacturing process route, but the technical details adopted by different companies are still different.
Non-melting treatment and high-temperature sintering are relatively important process links, and have a great impact on fiber performance. The pioneer conversion method usually includes four major processes, including the synthesis of the pioneer, the melt spinning of the pioneer, the non-melting of the raw wire (to prevent the fiber from melting during the pyrolysis process), and the high-temperature sintering of the non-melting fiber (the non-melting fiber is heated to 1200-1500°C in vacuum or inert gas, and the methyl group of the side chain and hydrogen are removed at the same time, leaving only the silicon-carbon skeleton to form a fiber with a β-silicon carbide structure). Among them, the non-melting of the polycarbosilane (PCS) raw wire and the high-temperature sintering are two more important process links. Early processes used oxidation to non-melt PCS raw silk, but obtained a generation of SiC fiber with higher oxygen content, with a significant decrease in tensile strength at high temperatures. After that, after using electron beam radiation crosslinking technology for non-melting treatment, low-oxygen second-generation SiC fibers were obtained, with good high-temperature performance.
With the advancement of technology, the performance and preparation cost of SiC fibers are constantly increasing. The typical representative of the first generation of SiC fibers in is the universal grade NicalonNL202, which still has good thermal stability at 1000℃; the typical representative of the second generation is Hi-Nicalon, which has good thermal stability at below 1300℃; the typical representative of the third generation is Hi-NicalonS and Tyranno series, which also has good thermal stability at above 1300℃.Overall, SiC fibers have developed from the first generation to the third generation, and their preparation temperature and thermal stability are developing towards a higher direction, with the fiber oxygen content lowering, density higher, diameter lowering, and fiber production costs greatly increased. There are different technical directions in the preparation process of pioneer body conversion method, and the cost of different technical routes varies greatly, but overall, the cost of third-generation SiC fibers is significantly higher than that of first-generation and second-generation.
Japan took the lead in conducting research. my country started at the same time as the United States and Germany, but its progress lags behind in the same year-on-year
Japan was the first to carry out the scientific research and production of SiC fibers. 975 and 1976, Professor Yajima of Tohoku University of Japan published articles to propose the synthesis method of polycarbosilane (PCS) and the results of the preparation of SiC fibers by thermal decomposition and conversion from PCS. Later, Japan Carbon Company and Ube Hitosan Company successively purchased Professor Yajima's patents on the manufacturing of SiC fibers and titanium-containing SiC fibers. In 1982, Japan Carbon Company produced the first batch of industrial silicon carbide fibers Nicalon100 series, and then launched the Nicalon200 series fibers, becoming a typical representative of a generation of SiC fibers. In 1987, Ube Hitosan Company used polytitanium carbosilane (PTCS) as a pioneer and used air crosslinking technology to prepare titanium-containing SiC fibers and achieved industrialization, named "TyrannoLox-M". Since then, the two companies have continuously improved raw materials, process flow and parameters, and have successively realized the industrialization of first-generation, second-generation and third-generation SiC fibers.
Georgia and other countries have improved and innovated based on Japanese technology and have also achieved industrialization. Faced with the success of Japanese companies in SiC fiber development, the United States and Germany are not willing to lag behind. In addition to using Japanese SiC fibers to carry out a large number of SiC fiber composite preparation technology research and development, they have also begun to develop SiC fiber preparation technology and have carried out process innovation. For example, DowCorning, the United States, introduced boron during the preparation of SiC fibers, and then sintered at a high temperature of 1800℃ to produce polycrystalline SiC fibers containing boron. The fibers have high strength and modulus, good heat resistance, and have made continuous fibers, and the industrial product is named "Sylramic"; BayerAG, Germany, took a different approach, based on the idea of amorphous fibers, became a new pioneer of polyborazane (PBSN) in the 1990s, and was thermally decomposed and converted to produce SIBN3C fibers that can still maintain amorphous state at 2000℃. Its mechanical properties and heat resistance are excellent, and continuous fibers have been produced. The industrial product is named "Siboramic".
National University of Defense Technology is the first unit in China to carry out the pioneer body transformation method to prepare SiC fibers and titanium-containing SiC fibers, with strong technical strength. was conducted as early as 1980 by the National University of Defense Technology. In the past 40 years, a series of research has been carried out on the preparation route of SiC fiber, the synthesis of key raw materials, the preparation process technology and production line construction, and has made significant progress. At present, the first-generation SiC fiber of KD-I type (the comprehensive performance is close to the level of Japanese Nicalon fiber), KD-II type second-generation SiC fiber, KD-S type and KD-SA type third-generation SiC fibers, and at the same time, absorbing SiC fibers and wave-transmissive fibers have been successfully developed for different functional needs. KD-SA is an aluminum-containing SiC fiber. KD-SA fiber has better high-temperature oxidation resistance in the air. The strength retention rate is 55% after 100 hours of heat treatment at 1300℃, far exceeding Hi-Nicalon (23%).
Xiamen University Special Advanced Materials Laboratory, under the guidance of Academician Zhang Litong of Xi'an University of Technology, began the preparation and development of low-oxygen and high-carbon continuous SiC fibers in 2002. In 2004, the laboratory broke through the key technology of fiber preparation, and the performance of fixed-length fibers was close to the level of similar products in Japan. Since then, the industrialization research of continuous SiC fibers has begun.
Ningbo Institute of Materials, Chinese Academy of Sciences and Central South University have also broken through the third generation of SiC fiber preparation technology .According to the official website of the Chinese Academy of Sciences, the SiC fiber research team of the Special Fiber Division of the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences has undertaken the task of developing the third generation of silicon carbide fibers since early 2015. It has independently developed spinning equipment and has made important progress in the development of continuous silicon carbide fibers. It has opened up the entire technical route from pioneering body preparation, melt spinning, non-melting to sintering. The next step will be to further improve the process to achieve the preparation of high-performance continuous silicon carbide fibers. According to the official website of Central South University, the School of Aeronautics and Astronautics of Central South University cooperated with Hunan Boxiang New Materials Co., Ltd. in 2016 to build a Hunan Provincial Engineering Laboratory for high-performance silicon carbide fibers and their composite materials. At present, the laboratory has successfully prepared the third generation of doped silicon carbide fibers, and the prepared continuous silicon carbide fibers have a service temperature of 1250℃ (under air atmosphere).
Japanese companies are the main manufacturers of SiC fibers in the world. Domestic industrialized production is in its infancy
Foreign third-generation SiC fibers have been industrialized. Japan's NipponCarbon and UbeIndustries are the main manufacturers of SiC fibers in the international market, with a total output accounting for about 80% of the world. The first, second and third generation SiC fibers abroad have been industrialized. Among them, the production of pure SiC fibers (grade Nicalon) of NipponCarbon and UbeIndustries' SiC fibers (grade Nicalon) of titanium, zirconium, aluminum and other types of SiC fibers (grade Tyranno) both reach 100 tons and remain basically stable. DowCorning, the United States, has successfully developed boron-containing SiC fibers, with the grade Sylramic. The technology has been transferred to COI Ceramics, the output is unknown. There has been no reports of industrial production of SiBN3C fiber from BayerAG in Germany.
013 GE predicts that the demand for ceramic matrix composites will increase by 10 times in the next 10 years, and in 2016, it will invest in the construction of a factory to produce SiC fibers and composites. In June 2016, GE Aviation Group obtained a fiber production technology license from Japan's NGS Advanced Fiber Company and invested US$200 million to build two new SiC material factories in Huntsville, one of which produces SiC fiber and the other uses SiC fiber to prepare ceramic matrix composite materials. The factory is scheduled to be put into production in 2020. Once fully put into production, the two plants are able to produce 10 tons of SiC fiber and 20 tons of SiC fiber reinforced composites each year. GE is working hard to apply SiC-based composite turbine blades to new generation aircraft engines such as GE9X, LEAP-X1C, and F414 modifications.
Domestic SiC fiber industrialization has made significant progress, but it is still in its infancy and has a large gap with developed countries such as Japan. According to the "Research Progress in Research on Continuous Silicon Carbide Fiber Reinforced Silicon Carbide Ceramic Matrix Composite Materials" published by AVIC Composites in December 2016, "Domestic SiC fiber industrialization development mainly includes two five-year plans, the "Eleventh Five-Year Plan" and the "Twelfth Five-Year Plan". The research and development units mainly include National University of Defense Technology, Xiamen University (including Torch Electronic Technology Co., Ltd.) and Suzhou Sailife Ceramic Fiber Co., Ltd. With the strong support of the country and the efforts of relevant scientific research institutions, the first generation of SiC fiber engineering has been achieved, breaking through the key technologies for the development of the second generation of SiC fibers. At present, the second generation of SiC fibers in China is in the pilot stage, with a production capacity of 1 ton/year. Overall, the domestic SiC fiber research foundation is relatively weak, although it has achieved It has made significant progress, but the gap between the advanced level of developed countries such as Japan in terms of quality stability and industrialization capabilities is huge. "
National University of Defense Technology is the first unit to establish a SiC fiber pilot production line in China. It has solved the problem, but the production capacity is limited. In the 1990s, the National University of Defense Technology completely independently established a KD-I continuous SiC fiber pilot production line with an annual output of 100kg, which was later expanded to an annual output of 500kg, and has been supplied to aviation, aerospace, weapons and other departments, and has been used in the fields of aero engines, space debris protection, etc. Since then, the National University of Defense Technology has established a pilot production line of KD-II fibers with an annual output of 1 ton. KD-II fibers have good braiding properties and can be used for braiding inner cones, slaloms and pins. They have also been mass-produced for applications in aviation, aerospace, weapons and other departments.
…
SiC fiber reinforced composite material preparation technology is gradually maturing, promoting product application
SiC fibers can be woven into fabrics, or can be composited with metals, resins, ceramics, etc. to prepare into composite materials, with great application potential in many fields such as aerospace. SiC fibers have thin diameters and good toughness, and are easy to woven into flat fabrics such as plain weaves, twills, diamonds, and perforated holes. They can also be woven into various specifications of flat panels, I-beams, T-beams, pipes, rods, fiber ropes and other variable-section three-dimensional fabrics, etc., and can also be made into various specifications of SiC fiber felts. In addition, composite materials can be made by composite with resin, metal, and ceramic. Specifically, SiC fiber-reinforced metal-based composite materials can replace metal materials to achieve lightweight and high strength. For example, SiC fiber-reinforced Al-based composite materials with a fiber volume content of 30%, with high bending strength and tensile strength, while reducing weight by 40%. It can be used to manufacture tail gun barrels for missiles, etc.; Composite materials composed of SiC fiber and epoxy resin have higher compression strength and impact strength, excellent wear resistance, and have excellent electrical properties, which can make them widely used in radar radomes, aircraft structural materials, and various structural wave absorbing materials. SiC fiber-reinforced ceramic matrix composite materials are mainly used in heat-resistant components of rockets and aircraft jet engines, insulation tiles for space shuttles, etc.
Continuous SiC fiber-reinforced silicon carbide ceramic matrix composite (SiCf/SiC) preparation technology has become mature, and some technical achievements have been successfully applied to the hot end components of aero engines. Commonly used preparation technologies for SiCf/SiC mainly include chemical vapor permeation method (CVI), polymer impregnation and cracking process (PIP), melt impregnation process (MI), etc. Among them, the MI process has obvious advantages and is an ideal choice for low-cost and engineering technology for SiCf/SiC composite materials.
Foreign SiCf/SiC composite material preparation technology is relatively mature, and relevant processes have also been broken through in China. Japan is the first country to carry out PCS and continuous SiC fiber research, and its PIP preparation process has significant advantages; Germany and the United States use MI technology to achieve mass production of SiCf/SiC composite components; France mainly uses CVI technology and has internationally leading technical level. China Aviation Industry Composite Materials Center and Northwestern Polytechnical University use PIP process and CVI process respectively to develop SiCf/SiC composite materials. Shanghai Institute of Silicate and Central South University have made significant technological breakthroughs in MI process. Overall, my country has the capacity for component development and small-scale production, but there is still a significant gap with Western developed countries in terms of industrialization.
is currently mainly used to prepare high-temperature structural composites, high-temperature stealth materials and advanced nuclear energy materials
The United States, Japan and other countries have begun to use SiC fiber and SiC fiber reinforced composite materials in high-end equipment, mainly used in the preparation of high-temperature structural composites, high-temperature stealth materials and advanced nuclear energy materials. Japan and the United States have achieved industrial production of high-performance continuous SiC fibers, and are used in the combustion chambers of aerospace engines, nozzle diversion blades, turbine blades, turbine shell rings, tail nozzles, aerospace aircraft wing leading edges and rudder surfaces, hypersonic weapon propulsion systems, and nuclear fuel clad tubes.
SiC fiber high-temperature structural materials are mainly used in the aerospace field, including the thermal end components of the engine (mainly used in combustion chambers and turbines) and the thermal protection systems of aircraft. aircraft engines require an increase in thrust-weight ratio and reduce fuel consumption. The fundamental measure is to increase the turbine inlet temperature and reduce structural weight, which requires the transformation of high-temperature structural materials of aircraft engines from high-temperature alloys and single crystals to ceramic matrix composite materials.In high temperature environment, SiCf/SiC composite materials can not only maintain excellent specific strength, but also reduce the weight of turbine blades and reduce cooling devices. Compared with high-temperature alloy blades, it has stronger heat corrosion resistance, which is of great significance to improving the thrust-to-weight ratio of aircraft engines. GE and PW use SiCf/SiC composite materials to prepare combustion chamber bushings, and can work more than 10,000 hours in 1200℃ environment; GE Aviation has developed a SiCf/SiC composite combustion chamber flame cylinder, which can work for more than 9,000 hours in 1200℃ environment; GE and R-R jointly developed the F-136 engine for the F-35 fighter jet, using SiCf/SiC composite material third low-pressure vortex guide blades, and 10 currently have Test records of more than ten thousand hours.
On February 10, 2015, GE, the United States, successfully verified the world's first rotating low-pressure turbine component on the F414 turbofan engine verification machine, pointing out the direction for the application of SiCf/SiC composites in aircraft engines and gas turbines. On June 16, 2015, the ceramic matrix composite tail nozzle designed by Safran Group of France completed its first commercial flight with a CFM56-5B engine, passing the airworthiness certification, marking the arrival of the era of SiCf/SiC composite materials for high-temperature components of aircraft engines.
In terms of thermal protection, Japan uses SiCf/SiC composites as the thermal protection systems of the plane wings and cutting-edge curved wings of the aerospace shuttle HOPE-X; France uses SiCf/SiC composites as the cover insulation layer of the aerospace shuttle HERMES; Lockheed Martial Arts has developed more than 30 heat-resistant tiles developed by SiCf/SiC composites on the USS Columbia, USA, and has good application effect. Since 1981, Columbia has successfully carried out nearly 30 missions.
SiC fiber has semiconductor properties and is an important material for radar wave absorption. It also has high-temperature oxidation resistance. It is suitable for use as a high-temperature stealth material. It can be used to manufacture head cones, tail wings, fish scale plates and tail nozzles of stealth aircraft and cruise missiles. As for the French "Phantom 2000" fighter's M53 engine, the inner side and tail nozzle of the fish scale plate, and the four right-angle tail wings of the F-22 stealth fighter produced by Lockheed Martin.
continuous SiC fiber is considered to have broad application prospects in the field of advanced nuclear energy due to its good irradiation stability. Currently, SiC-based SiC fiber composite material (SiCf/SiC) has been used in the design of nuclear fusion reactors, mainly used on the first wall of the cladding, flow channel plug-ins, control rods, and filters. For example, the conceptual design of DRREAM and A-SSTR2 cladding uses SiCf/SiC composite as the first wall/clad structural material; the conceptual design of PPCS-C cladding uses SiCf/SiC composite to make runner plug-ins; the filter design of ARIES-AT in the United States uses SiCf/SiC composite as structural material.
Domestic fiber mass production and composite preparation technology are gradually maturing, and it is expected to open up a broad downstream market space
Domestic fiber mass production and composite preparation technology are gradually maturing, which is expected to drive the rapid growth of downstream applications. The performance of the third-generation SiC fibers has basically met the needs of practical applications. Research on ceramic matrix composite materials (CMCs) with the third-generation SiC fibers as reinforcement has been widely carried out. It can not only be used in heat-resistant components of aerospace engines, thermal protection material systems for reusable carriers, and hypersonic weapon propulsion systems, but also has wide application potential in the fields of nuclear energy, high-speed brake pads, gas turbine thermal end components, high-temperature gas filtration and heat exchangers. With the mass production of the first, second and third generation SiC fibers and the gradual maturity of composite preparation technology, it is expected to drive the rapid growth of downstream applications such as aviation, aerospace, and nuclear power in the future.
my country has carried out research on SiC fiber composite materials for engines, achieving weight loss of engines. According to the PLA Daily on July 1, 2017, a private enterprise used continuous silicon carbide fiber material to make a certain type of engine nozzle adjustment plate, which increased the high temperature resistance by 150 degrees and reduced the weight by 8 kg. We believe that in the future, with the bulk production of domestic engines and the development and advancement of new generation fighter jets, the demand for SiC fibers and their composite materials will gradually increase.
. quartz fiber: The development of the aerospace industry has driven a rapid increase in demand quartz fiber refers to special glass fibers with silica content of more than 99.95% and wire diameters of 1~15 microns. It has high heat resistance and can be used for a long time below 1050℃. The short-term maximum service temperature reaches 1200℃, and the softening temperature is 1700℃. The temperature resistance is second only to carbon fiber. Quartz fibers have excellent electrical insulation and their dielectric properties vary less with temperature. Quartz fibers can maintain the lowest and stable dielectric constant and dielectric loss in high-frequency and working areas below 700℃. These excellent properties make them structural enhancement, wave-transmitting and thermal insulation materials for key parts of aerospace vehicles.
mainly produces continuous quartz fibers: rod wire drawing, melt wire drawing and sol-gel method, among which industrial production is mainly rod wire drawing. rod drawing method is generally made of pure natural crystal refining and processing into molten silica glass rod drawing. After the drawing is completed, it is prepared into different quartz products, such as untwisted rovings, twisted yarns (including single-strand and combined yarns), fiber cloth, fiber sleeves, chopped fibers, fiber cotton, fiber felt and fiber bricks, etc.
quartz fiber is mainly used as the radiation-transmissive material of the radar cover and the spacecraft heat insulation material
The development of airborne radar has made its radomes more and more demands on mechanical properties and wave-transmissive properties, and the main factor that determines these two properties is the composite materials used to prepare the radomes. The main functions of the airborne radar radome are: ensuring that the radar antenna system works without environmental interference, avoiding damage to the radar antenna in harsh flight environments; passing through electromagnetic waves; and improving the aerodynamic shape of the aircraft. The composite materials used in the radome have a great impact on the mechanical properties and wave transmission properties of the radome. The better the bending and impact resistance of the composite material, the stronger the ability of the airborne radar radome to carry air loads, and the better the ability to resist the impact of foreign objects during flight; the lower the dielectric constant (ε) and dielectric loss tangent value (tanδ) of the composite material, the better its dielectric performance, and the better the wave transmission performance of the radome.
quartz fiber has good wave transmissive performance and is suitable for high-performance airborne radar covers. It has been used in US F-15, F-22 and other fighter jets. Commonly used reinforcement fibers for airborne radar radomes include ordinary glass fibers, quartz fibers, high silicone oxygen glass fibers, etc. Among them, glass fiber reinforced resin-based composite materials are the most widely used radome material in actual production. The application frequency range is mainly within the 10GHz range. For high-frequency radome (10-20GHz), due to its high emission frequency and short wavelength, the radome has a large wave transmission loss. The dielectric properties of quartz fibers are better than ordinary glass fibers. The ε value and tan δ value are the lowest in the glass fiber system and basically do not change within a wide frequency band range. Therefore, the wide-frequency wave transmissibility of the radome can be achieved. Although the price is high, most advanced foreign radar masks have used quartz fiber as reinforcement materials.
1. Ordinary glass fiber: E glass fiber is the earliest wave-transmissive reinforcement material used in airborne radar radomes. It has high tensile strength, good aging resistance, good dielectric properties, and the lowest price. However, with the development of airborne radar antenna technology, some of its performance can no longer meet the specific usage requirements, so improved models have been produced, resulting in high-strength glass fiber (S glass fiber), high-modulus glass fiber (M glass fiber) and low-dielectric glass fiber (D glass fiber). Among them, S glass fiber has the best mechanical properties among glass fibers, with a large dielectric loss tangent value, which can be used to prepare airborne radar radomes with high structural performance requirements and general dielectric performance requirements; M glass fiber has the highest modulus among glass fibers, but has a large dielectric constant, and is rarely used to prepare airborne radar radomes; D glass fiber is the earliest developed and utilized in foreign countries to manufacture radomes, and it has been widely produced in China. Its ε value and tan δ value are second only to quartz glass fibers, but its tensile strength and modulus are slightly lower, so it can be used to manufacture airborne radar radomes with high electrical performance requirements and general mechanical performance requirements.
2. High silicone glass fiber: High silicone oxygen fiber is a reinforcing material unique to Russia for wave transmissive composite materials. It has good heat resistance and excellent dielectric properties. It is very suitable as a reinforcing material for tactical missile radomes and is also commonly used to prepare airborne radar radomes. High silicone oxygen fibers have similar strength to general fibers, and their cost performance is between quartz fiber and E glass fiber.
3. Quartz fiber: Quartz fiber is the most commonly used reinforcement fiber for high-performance airborne radomes. It has excellent thermal insulation performance, is very compatible with phenolaldehyde resins and epoxy resins, and has the rare characteristic that the elastic modulus increases with the increase of temperature; its dielectric performance is very excellent, the ε value and tan δ value are the lowest among glass fibers, and it basically does not change within a wide frequency band range. Quartz fiber has been widely used in practice. For example, the first and second generation nasal radomes of the US F-15 fighter jets all use quartz fiber-reinforced cyanate resin composite material as the skin of the sandwich structure. The radomes of the foreign fourth-generation fighter jets (such as the US F-22 fighter jets) also use quartz fibers with excellent broadband performance.
quartz fiber is widely used in missile radomes. It is still constantly improving and improving at home and abroad.
is similar to aircraft radomes. The function of missile radomes is to ensure the normal operation of the missile-borne radar seeker during flight. The radome materials need to meet the requirements of missile mechanical properties, dielectric properties, thermal shock resistance, rain corrosion resistance, life, and technology. Continuous fiber reinforced ceramic matrix composite materials can not only essentially overcome the brittleness of ceramic materials, but also retain the advantages of high strength, small thermal expansion coefficient and good thermal stability of ceramic matrix materials, it has become one of the main material systems for preparing high Mach number missile radomes in recent years. The ceramic fibers used mainly include glass fibers, quartz fibers, boron nitride (BN) fibers, silicon nitride (Si3N4) fibers, etc.
quartz fiber is the most commonly used high-temperature wave-resistant ceramic fiber for high-Mach number missile radomes in foreign countries, but it still has performance limitations and is constantly improving at home and abroad. S glass fiber, D glass fiber and high silicone oxygen glass fiber are the earliest materials for reinforcing missile radomes, but these ordinary glass fibers are limited by density and temperature resistance, making it difficult to meet the needs of preparing high Mach number missile radomes. Quartz fiber has excellent comprehensive performance and is an ideal reinforcement for wave-transmitting materials of high Mach number missile radomes. It is widely used. However, when the temperature reaches 900℃, the quartz fiber will undergo crystallization, and its strength will drop rapidly, greatly affecting the mechanical properties of the composite material. When the temperature reaches 1200℃, its reinforcement effect will basically disappear, which seriously limits the application range of quartz fiber. Material improvements are constantly being carried out at home and abroad. For example, Philco-Ford and GE of the United States have prepared three-dimensional multidirectional quartz fiber fabric-reinforced quartz-based composite materials with a surface melting temperature of up to 1735℃ and are used in the United States' "Trident" missiles; Russia has developed quartz fiber-reinforced phosphate-based composite materials, which can maintain relatively excellent performance under temperatures up to 1800℃. It has been used in various types of cruise missiles, tactical, anti-missile missiles and aerospace aircraft.
quartz fiber is currently the most important wave-transmissive reinforcement fiber used in the medium and high Mach missile radome in China. is used to meet the needs of medium and long-range ground tactical and strategic missile radomes, and many domestic units have also successfully developed quartz fiber fabrics and composite materials. For example, Beijing FRP Research and Design Institute has studied quartz glass cloth reinforced phosphate composite materials, which can be used for use radomes with temperatures below 1200℃; the three-dimensional quartz fiber reinforced quartz matrix composites developed in China have been practically applied on certain models in the aerospace field. Quartz fiber is currently the most important wave-transmissive reinforcement fiber used in medium and high Mach missile radome in China. However, with the development of medium and long-range precision-guided missiles, the flight time of the missile has been further increased, and the reentry speed can be as high as more than 20 Mach, which makes the working temperature of the missile radome a sharp increase, and quartz fiber is difficult to meet this working condition. Therefore, other types of high-temperature wave-resistant ceramic fibers such as Si3N4 fiber, BN fiber, SiNO fiber and SiBN fiber are also being developed in China.
quartz fiber can be used in spacecraft as a thermal protection material
ceramic fiber rigid thermal insulation tiles are the most important thermal protection material for US space shuttles and are also used in new hypersonic speed vehicles such as X-37 and X-51. ceramic fiber rigid thermal insulation tiles have high porosity and low capacities. They have stable shape and certain strength at high temperatures. They also have excellent radiation heat dissipation, heat insulation, anti-shrinking and maintain aerodynamic appearance. They are currently one of the most important thermal protection materials for US space shuttles. The application area accounts for 68% of the total thermal protection surface of the space shuttle. 24,300 ceramic fiber thermal insulation tiles are pasted on the surface of the world's first space shuttle, Columbia. In recent years, ceramic fiber rigid thermal insulation tiles have also been used in the thermal protection systems of hypersonic vehicles such as X-37 and X-51.
Rigid thermal insulation tiles have been developed for 4 generations, and quartz fibers are important reinforcement fibers. The development of American ceramic fiber rigid thermal insulation tiles began in the 1960s. Lockheed developed the first generation of ceramic fiber thermal insulation tiles using quartz fiber as reinforcement fibers in 1972, and expanded production in 1975. The development of rigid heat insulation tiles in the United States has been roughly four generations, and their heat resistance has been continuously improved. A large number of quartz fibers are used as reinforcement materials. This is mainly because quartz fibers can melt and absorb heat at high temperatures, and further use the molten liquid layer to block heat flow. It is a typical representative of melted ablation heat-proof materials.
Aerospace industry development is expected to drive the demand for quartz fibers
Medium- and long-range strategic and tactical ballistic missiles are the main combat equipment of the Rocket Force, and the air defense and anti-missile system is the main weapon of the Air Force air defense and naval air defense ships; cruise missiles span three branches of the Rocket Force, the Air Force and the Navy. We believe that under the stimulation of the demand for downstream services such as the land, sea, air, and rocket forces, there will be a large demand for missiles in the future. In the future, the Rocket Force will actively strengthen the construction of medium and long-range precision strike forces based on the strategic requirements of "maintaining nuclear and regular nuclear weapons and all-region deterrence warfare", enhance strategic checks and balance capabilities, and missile defense equipment is expected to maintain a steady and rapid growth trend. Quartz fiber can be used in missile radomes and shells, and there is great potential for demand growth in the future.
As mentioned above, my country's military aircraft technology is mature and demand is strong, and it has entered the turning point of mass production. Quartz fiber is a commonly used fiber material for military aircraft radar shields. With the increase in mass production of military aircraft, the demand for quartz fiber will also grow rapidly.
6. Key companies in the domestic military composite industry chain
Filiphi: Focus on high-end quartz, semiconductor and military industry downstream demand growth potential
Guangwei composite: National Light leads the development of the carbon fiber industry, and the military and civilians have broad application prospects
Zhongjian Technology: Military ZT7 Core Supplier, Actively develop other types of carbon fiber
Torch Electronics: Military MLCC Core suppliers, layout of new materials helps take off
Longhua Technology: business transformation and upgrading, external layout of military composite materials
Chujiang New Materials: Leading copper processing, actively layout high-end equipment and military materials
AVIC High-tech: dual-wheel drive of aviation composite materials and high-end manufacturing, and the prospects for military-civilian integration are broad
...
(Report source: Huatai Securities)
Please log in to the Future Think Tank www.vzkoo.com to obtain the report.
Log in now, please click: "Link"
