Due to the low density, high specific strength and high specific stiffness of composite materials, fuel consumption and noise can be effectively reduced, and the use of composite blades has become the development trend of civil aviation engines. The following is a model essay on related papers that I recommend to you, hoping to help you. More exciting content can be found at www.oh 100.com/bylw.

Since the beginning of the new century, technology in many fields has made great progress, especially with the progress of transportation, large civil aircraft began to become the main force of transportation, so countries began to pay more attention to the development of large aircraft, and aviation industry began to become an important standard to measure a country's comprehensive national strength. Engine technology is the key and core technology of large aircraft research and development. With the development of civil aviation industry, the core technology of civil aviation aircraft? Engine technology has also developed rapidly, in which composite blades have been gradually applied to many civil aircraft models.

Keywords: civil aviation; Composite materials; Engine; fan blade

In the past, aircraft engine blades were mainly made of metals and alloys. With the appearance of new materials, composite materials have been applied to aircraft engine blades. Compared with metal materials, it has the advantages of light weight, low noise and high efficiency. The number of composite blades is less, which can effectively resist vibration and damage, and it is also superior in bird impact resistance, meeting the airworthiness requirements of modern civil aviation. Therefore, composite blades have attracted the attention of the world's major engine manufacturers, and are gradually popularized and applied.

1 application of composite blades

The manufacturing technology of composite blades mainly includes prepreg/molding technology and 3-DWOVEN/RTM technology. Typical examples of prepreg/molding technology are the composite fan blades of GE90, GEnx, TRENT 1000 and TRENTXWB engines, while the composite fan blades of LEAP-X engines are molded by 3D-WOVEN/RTM technology.

1. 1 prepreg/molded blade

The representative blades using this composite material are GE90 engine and GEnx engine (GE, USA). Luo company is also carrying out related research and development. (1)GE90 engine. This type of engine is a super thrust engine developed by ge Company in 1990s, and it is one of the earliest composite blade engines used in civil aviation abroad. The composite blade of the engine adopts prepreg/molding technology, and the blade gradually becomes thinner from the inside out, with the thinnest tip thickness. In addition, the blade body is coated with anti-corrosion coating (polyurethane), the blade back is coated with universal coating, and the leading edge is wrapped with titanium alloy, which improves the bird impact resistance of the blade. In order to prevent the composite from delaminating in operation, fiber stitching technology is used to strengthen the trailing edge and tip of the blade. The blade root tenon is a triangular dovetail joint, and its surface is coated with wear-resistant material, which reduces the friction coefficient of the tenon. GE90 uses 22 composite blades. Compared with titanium alloy hollow blades, composite blades are lighter in weight and higher in strength. After more than ten years of operation, it is proved that composite fan blades are suitable for demanding commercial flights. (2)GEnx engine. Compared with GE90, the composite blade material and molding process used in this engine have not changed much. On this basis, GEnx optimized the structural design of GE90 composite blades. GEnx is mainly made of the third generation GE composite material, and its appearance is similar to that of GE90- 1 15B engine. However, due to the new generation of three-dimensional flow design, the number of blades is reduced to 18, and the total mass is further reduced. The tip and leading edge of the blade adopt titanium alloy sheath, and wear-resistant gasket is added at the tenon root of the blade to facilitate later maintenance. (3) With the application of composite materials in civil aviation engines, Britain? Luo also began to shift its attention from titanium alloy blades to composite blades. It is cooperating with GKN Group to develop carbon fiber reinforced composite blades, which are as thin as titanium alloy blades and meet the standards of mass production, cost and robustness of civil aviation engines. At present, this kind of carbon fiber fan blade has completed the ground test including blade flying out and bird impact test.

1.23-DWOVEN/RTM molding composite blades

The strength requirement of fan blade medium thrust engine is higher, so Snecma will apply carbon fiber to strengthen the composite materials in LEAP-X during the development of CFM56 series engines. Compared with GEnx and GE90, the carbon fiber thin-layer laying technology is different. The RTM process used by Snecma in manufacturing LEAP engine blades is to pre-weave carbon fibers. Before resin injection and blade high-pressure forming, carbon fibers have become 3-DWOVEN structures. Snecma Company entrusts AEC Company to manufacture composite blades. Because AEC company has a high degree of automation in manufacturing, it only takes 24 hours from preparing three-dimensional prefabricated parts to completing the manufacture of the whole blade. Compared with CFM 56 engine, 3-DWOVEN/RTM technology is adopted in the blade forming of LEAP engine. The former adopts more technologies in structure, while the latter adopts composite materials, which can effectively reduce engine weight, improve fuel efficiency and reduce emissions and engine noise. At present, the LEAP-X engine has begun to attract the attention of various domestic passenger planes, and will be gradually popularized in China in the future.

2 development trend of composite blades

Due to the low density, high specific strength and high specific stiffness of composite materials, fuel consumption and noise can be effectively reduced, and the use of composite blades has become the development trend of civil aviation engines. The key factors restricting the large-scale application of composite blades are preform preparation and composite molding technology.

2. 1 Precast preparation

One of the difficulties in manufacturing composite blades is to prepare preforms. There are two common methods to prepare preforms abroad: one is to use IM7/855 1-7 and IM7/M9 1 as prepregs, and prepare them by laser positioning manual/automatic forming technology, which is suitable for preparing fan blade preforms of turbofan engines with large thrust and large blade diameter; The other is that IM7 carbon fiber is pre-impregnated by 3D-WOVEN/RTM automation technology, which is mainly used to prepare the fan blade preform of small thrust turbofan engine. In the past, the technology of laser positioning and manual stacking was used to manufacture preforms, while GKN developed automatic tow laying equipment (AFP) to realize the automatic forming of preforms. Luo? TNENT series engine composite fan blades were developed by GKN company's automatic fiber bundle laying equipment, which realized the automatic forming of composite blade preforms and used ultrasonic knives to cut the preforms. Snecma Company took the lead in proposing non-allowance preforming technology, preforming pre-deformation technology and highly automated preforming preparation technology. Snecma's 3DW/RTM preforming technology for fan blades can reduce the possibility of delamination defects in traditional two-dimensional fan blades, making the top of the blades thinner and the roots thicker. The variable cross-section forming technology of continuous warp yarn is adopted to improve the bearing capacity of preform; High-pressure water jet is used to cut preforms without allowance.

2.2 molding technology RTM

Injection molding and compression molding are two popular composite blade forming technologies in the world. Although there are some technical differences between them, they can both be called closed mold forming technology. The blades of turbofan engine are hyperboloid, with large torsion and relatively complex structure. Conventional forming technology can not meet the machining accuracy of blades, while closed die forming technology has high forming accuracy and can meet the requirements of turbofan engine for blade manufacturing, so it has gradually become the mainstream technology of composite blade forming at present. With the gradual development of technology, at present, foreign countries begin to use composite molds instead of metal molds to ensure that molds and parts can maintain the same thermal expansion coefficient in production and processing, and then obtain higher dimensional accuracy of parts. In addition, digital simulation technology is introduced into the composite blade forming technology, so as to guide the forming process in the early stage of technical research, avoid risks reasonably, shorten the development cycle and reduce the development cost.

3 Conclusion

Composite materials have become the mainstream materials of civil aviation engine blades because of their superior characteristics, and with the development of technology, the manufacturing efficiency of composite engine blades is higher and the degree of automation is more advanced. In the future, high precision, reliability and consistency will become the main direction of composite blade production and research. Commercial engines are also used in the large passenger aircraft independently developed by China, which provides opportunities for R&D and composite blades manufacturing in China. Although composite materials are still in the initial stage of application in China's aero-engine manufacturing and the manufacturing of composite blades is only in the initial stage, with the efforts of Chinese technicians, the turbofan engine with composite blades independently developed by China will surely occupy a place in the world aviation field.

References:

[1] Li Jie. Development and technology of GE composite fan blades [J]. Aeroengine, 2008,34 (4): 54-56.

Father he. Carbon fiber and graphite fiber [M]. Beijing: Chemical Industry Press, 20 10: 1- 16.

Zhao Yunfeng. Application of advanced fiber reinforced resin matrix composites in aerospace industry [J]. Dual-use technologies and products, 20 10/0,37 (1): 4-6.

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