On March 1, 2021, China Eastern Airlines and COMAC formally signed a C919 large passenger aircraft purchase contract in Shanghai. The first batch of 5 C919 large passenger aircrafts will be introduced, marking that the domestic large aircraft is about to enter the era of commercial operation.
China Eastern Airlines will become the world’s first airline to operate the C919 large passenger aircraft after the establishment of the One, Two and Three Airlines to operate ARJ21. After the signing of the purchase contract, the two parties will dock as soon as possible and carry out preparations before the aircraft is put into operation Work includes the negotiation and signing of new aircraft type supplementary operation certification, professional training, and customer support guarantee agreements. The two parties will work together to intensify cooperation in the fields of aircraft import and export, aviation material maintenance, logistics and warehousing, new technology applications, aviation material support, maintenance support, and optimization of flying mechanisms to ensure the high-quality operation of the first batch of aircraft.
What composite materials are used in C919?
In the more than one hundred years of development of the aviation industry, materials and aircraft have been continuously developing under mutual promotion. From wooden airplanes to metal airplanes, and now that composite materials have become a technological high ground for civil aircraft manufacturers, every change in aviation materials will promote a significant improvement in the technical level of the aircraft manufacturing industry. “One generation of materials, one generation of aircraft” can be said to be a true portrayal of the history of world aviation development.
The same is true for China’s civil aircraft industry. According to Wu Guanghui, chief designer of C919 large passenger aircraft, the application of new materials is a major technical highlight of C919. On the C919 aircraft, the third-generation aluminum-lithium alloy was used on a large scale for the first time in my country. The application range of composite materials covers the rudder and other secondary bearing structures and the plane’s flat tail and other main bearing structures. In addition, driven by the C919 project, my country has made many major breakthroughs in the field of aviation materials, and new material processing techniques and infrastructure construction have also made a qualitative leap.
The Way to Select Materials for C919
As a newly developed aircraft, the C919 large passenger aircraft fully considers the maturity and advancement of materials in terms of structural material selection. The purpose of this is to ensure the competitive advantage of the C919 as a new generation of narrow-body passenger aircraft on the one hand, and on the other hand. Consider the reliability and ease of maintenance of the aircraft in line operation in the future. After a large number of tests and rigorous demonstrations, on the C919 aircraft, in response to the different requirements of the main structural parts, COMAC has selected three major new aviation materials: carbon fiber composite materials, third-generation aluminum-lithium alloys, and titanium alloys.
Aluminum-lithium alloy has the characteristics of low density, high strength and excellent damage tolerance. Using it to replace conventional aluminum alloy materials can reduce the density of aircraft components by 3%, reduce weight by 10%-15%, and increase stiffness by 15%-20 %, so it is considered to be an ideal structural material for the new generation of aircraft.
The C919 large passenger aircraft uses the third-generation aluminum-lithium alloy, which solves the anisotropy problem of the second-generation aluminum-lithium alloy, and the yield strength of the material is also increased by 40%. The fuselage skin, long truss, floor beams, seat slides, boundary beams, and cabin floor support columns of the C919 aircraft all use the third-generation aluminum-lithium alloy, and its airframe structure weight accounts for 7.4%, which is comprehensive The gain of 7% of weight loss is at the leading level in the world.
At present, the composite materials used in civil aircraft are mainly carbon fiber reinforced resin matrix composite materials, which have the advantages of high specific strength, high specific modulus, excellent fatigue resistance, and corrosion resistance. This material is lighter than aluminum and harder than steel. Its density is 1/4 of iron, but its strength is 10 times that of iron. The chemical composition is very stable, which not only helps reduce the weight of the aircraft, but also improves the overall performance of the aircraft. . Therefore, in some new models launched by Boeing and Airbus in recent years, the amount of composite materials has gradually increased.
Considering that in the design life cycle of 90,000 takeoffs and landings, the C919 has to withstand many “tests of freezing and steaming” of the aircraft body structure caused by temperature differences, and the corrosion resistance and fatigue resistance of the body structure materials are particularly important. In view of the above-mentioned advantages of composite materials, COMAC has also selected composite materials in the design of C919. Its application range covers rudder and other secondary load-bearing structures and aircraft flat tails and other main load-bearing structures, mainly including radome, front and rear edges of wing, movable wing surface, winglet, wing fairing, rear fuselage, tail and other components , The dosage reaches 11.5% of the body structure weight. Among them, the rear wing main box section and the front section of the rear fuselage use advanced third-generation mid-model high-strength carbon fiber composite materials. The use of composite materials in the main bearing structure, high temperature zone, and pressurized zone is also the first time in domestic civil aircraft development. More importantly, through a large number of verification tests, COMAC has initially established an advanced material and special material specification system, design allowable value system, and manufacturing process specification system with independent intellectual property rights and achieved high-standard production process control.
