What new materials are used in the large aircraft C919?

At 6:52 on May 14th, the C919 aircraft numbered B-001J took off from the 4th runway of Shanghai Pudong Airport and landed safely at 9:54, which marked that COMAC was about to deliver its first customerThe first flight test of the first C919 large aircraft was successfully completed.

C919 successfully made its maiden flight, and for a while, popular science posts on the Internet flooded the sky.

The meaning of C919

"C" - the first letter of the English abbreviation "COMAC" of COMAC, which also stands for "China", which also happens to form the sequence of the prefixes of "Airbus" and "Boeing"arrangement.

"9" - stands for "long."

"19" - represents a maximum passenger capacity of 190 seats.

According to the introduction, due to the large-scale use of advanced materials, the overall weight of C919 has been reduced by about 7%.For the development of domestic passenger aircraft, one of the keys is to improve the application level of advanced materials, and the amount of composite materials is an important symbol for judging the advanced nature of civil passenger aircraft.Therefore, C919 is considered "a milestone in the field of materials in our country".Let's take a look at the selection of C919.

Aramid honeycomb material

Aramid honeycomb material is used for the doors and cargo floor of the C919 large passenger aircraft, which is a lightweight and high-strength non-metallic biomimetic core product made of phenolic resin-impregnated aramid paper.It imitates the honeycomb design of bees and has a stable, lightweight structure and high specific strength, it has higher shear strength than foam core, and it is more corrosion resistant than metal honeycomb.

At the same time, the aramid honeycomb material also has high toughness, good fatigue resistance and fire resistance, and is an ideal composite material for civil aircraft.

2. Glass fiber composite materials

Compared with carbon fiber composite materials, the mechanical properties of glass fiber composite materials are slightly lower, but due to the high dielectric constant of carbon fiber, it will affect the radar work. The radome of the C919 large passenger aircraft uses glass fiber composite materials.

Other parts that are less stressed, such as the flaps, also use fiberglass composites.Because the cost of glass fiber composite materials is lower than that of carbon fiber composite materials, it can not only meet the design requirements, but also reduce the manufacturing cost when applied to parts with less force.

3.T800 grade carbon fiber composite material

The C919 large passenger aircraft is the first civil aircraft in China to use T800 high-strength carbon fiber composite materials.Compared with T300-grade materials, T800-grade materials have higher strength, modulus, toughness, and better impact resistance. The parts with greater stress on C919, such as the rear fuselage and the vertical tail, use T800-grade materials.Carbon fiber composite material.

T300 belongs to the first generation of civil aircraft composite materials. Its resin matrix is ​​an untoughened brittle epoxy resin matrix, and its reinforcing fiber is T300 carbon fiber. Its tensile strength is about 3.5GPa and its tensile modulus is about 230GPa.T300 exhibits brittle material performance characteristics and is sensitive to delamination damage caused by impact load, so it can only be used for secondary load-bearing structures with little force.The T800 material used on the C919 adopts a toughened epoxy resin matrix, and the reinforcing fiber is T800 carbon fiber. The tensile strength and tensile modulus are about 50% higher than those of T300. It is also the most widely used composite structure for the main bearing structure of civil aircraft in the worldMaterial.

4. The third generation aluminum-lithium alloy

Al-Li 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 the weight by 10% to 15%, and increase the stiffness by 15%.%~20%, so it is considered to be an ideal structural material for a new generation of aircraft.

The C919 large passenger plane 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 stringers, floor beams, seat slide rails, boundary beams, cabin floor support columns and other components of the C919 aircraft all use the third-generation aluminum-lithium alloy, and the weight of the body structure accounts for 7.4%, which is comprehensively obtained.The gain of 7% weight loss is at the international leading level.

5. Carbon fiber composites and ceramic matrix composites

As the "flower of aviation", aero-engines can be said to be a complete experience accumulated in aviation technology and industry.The engine of the C919 is the LEAP-X1C engine.It uses 18 carbon fiber composite fan blades developed by Safran and ceramic matrix composite turbine components developed by General Electric Company of the United States.

6. aramid fiber

Aramid sulfone fiber is referred to as PSA fiber, which is composed of polysulfone amide.Its main features are excellent electrical insulation and heat resistance, in addition, high flame retardancy, limiting oxygen index over 30%, good chemical resistance, in addition to several highly polar solvents and concentrated sulfuric acid, inIt has good stability to chemicals at room temperature.Polysulfone can not only make a variety of high temperature resistant filter materials and insulating materials in high temperature and high pressure electrical appliances, but also can be processed into advanced flame retardant fabrics in transportation tools.

It is reported that the interior of the C919 cabin will use aramid fiber for the first time to make seat covers and door curtains, which will reduce the weight of the aircraft by more than 30 kilograms and save more than 10,000 yuan in cost per aircraft.

7. Rubber compound

In fact, aircraft tires are made of basically the same materials as car tires. The main difference is that aircraft tires use a higher strength rubber compound, so that aircraft tires can be inflated to 200 psi, which is equivalent to6 times the tire pressure of the car, the C919 uses Air X radial tires from Michelin.

This is the first time that composite materials are used in the main bearing structure, high temperature area and pressurized area in the field of civil aviation manufacturing in China, and the application of T800 grade high-strength carbon fiber toughened composite materials has been realized. It can be said that composite materials are used in civil aviation.The application in the field of machine manufacturing has accumulated valuable engineering practical experience.