Composite materials are widely used in aerospace and other fields because of their high specific strength, high specific stiffness, corrosion resistance and other excellent characteristics, but the expensive manufacturing costs have long restricted the expansion of the application of composite materials, such as carbon fiber and resin costs generally only account for 25% to 30%, while manufacturing costs accounted for 70% to 75%. On the other hand, the long molding cycle of traditional composite materials also restricts the monthly production rate of aircraft. Single-pass composite materials are widely used in aerospace and other fields because of their excellent characteristics such as high specific strength, high specific stiffness, corrosion resistance, etc., but expensive manufacturing costs have long restricted the expansion of the application of composite materials, such as carbon fiber and resin materials, which generally account for only 25% to 30%. The demand for Dao aircraft will reach 60 to 100 / month, such as the monthly production rate of A320 series aircraft in the next few years will reach 75. Therefore, in order to improve the competitiveness of composite materials in the aviation field, reducing manufacturing costs and improving manufacturing efficiency while ensuring weight reduction and structural performance will become the research hotspot of composite materials application.

In the world, the research and application of low-cost and rapid prototyping technology of composite materials has been attached great importance. In order to achieve the goals of expanding production capacity, reducing costs and protecting the environment, a series of technical research projects and plans have been initiated. In recent years, driven by the "green aviation" and "dual carbon" goals, reducing energy consumption, reducing noise and carbon emissions has become the future development goals of Chinese aviation. Therefore, it is imperative to improve the manufacturing efficiency and reduce energy consumption and carbon emissions of composite materials, which are the main materials of aircraft. This paper mainly summarizes and analyzes the low-cost and rapid prototyping technologies of composite materials commonly used in the aviation field, such as molding rapid prototyping, liquid molding technology and thermoplastic composite molding technology. The material system, process characteristics and engineering technology application at home and abroad are included, and the future research and development direction of rapid prototyping of composite materials are prospected.

At present, there are many manufacturing processes of composite structures, which can be applied to the production of different structures, but considering the industrial production efficiency and production costs of aviation, especially civil aircraft, it is urgent to improve the curing process to reduce time and reduce costs. Rapid Prototyping technology (Rapid Prototyping) is a new manufacturing method based on the principle of discrete and stacked molding, is a low-cost rapid prototyping technology, common rapid prototyping technology, liquid molding technology, thermoplastic composite material molding technology.

In recent years, thermoplastic composites have become a research hotspot in the field of composite materials manufacturing at home and abroad, because of their advantages of high impact resistance, high toughness, high damage tolerance and good heat resistance. The number of rivets and bolts of aircraft structure can be greatly reduced by thermoplastic composite welding, which can greatly improve production efficiency and reduce production cost. According to Airframer Collins Aerospace, a Tier 1 supplier of aircraft structures, non-autoclave molded weldable thermoplastic structures have the potential to reduce manufacturing cycles by up to 80% compared to metal and thermoset composite components.

2.3.1 Characteristics and properties of thermoplastic composite system

Compared with thermoset composites, thermoplastic composites have the following characteristics :(1) They have weldable characteristics, strong versatility, and short welding time, which can be applied to the connection of thermoplastic composites [7]; (2) Good toughness, fatigue resistance, high damage tolerance; (3) Long storage and operation life, long-term use; (3) High production efficiency, usually only a few seconds to a few minutes; (4) Recyclable and environmentally friendly.

At present, the thermoplastic resin systems commonly used in the aviation field mainly include PEEK, PEKK, PPS and so on. Developed earlier in foreign countries, and has been mature application, domestic start is late, but also realized the preparation of aviation grade CF/PPS and CF/PEEK plate.

At present, the most potential welding technologies for thermoplastic composite materials mainly include ultrasonic welding, induction welding, resistance welding and so on

With the successful application of thermoplastic composite and its welding technology in more and more international aircraft models, the feasibility of thermoplastic composite forming technology in civil aircraft structure manufacturing has been verified. At present, it is expected to see the figure of thermoplastic composite materials in the future domestic large aircraft. Therefore, China needs to establish a complete technical system to fill the key technical gaps, continue to solve the development of thermoplastic composite material system, the formulation of molding process specifications, the formation of various material standards and welding process specifications, the establishment of welding and weld quality evaluation programs and standards, the development of continuous automatic welding equipment.

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