Introduce
In the modern aerospace industry, the lightweight design of aircraft has become a key factor in improving flight performance and economic benefits. As the global demand for air travel continues to grow, airlines and manufacturers are under tremendous pressure to reduce fuel consumption, reduce carbon emissions and improve flight efficiency. Traditional metal materials, such as aluminum and titanium, although they have certain strength and durability, are heavy and have a negative impact on fuel efficiency. Therefore, seeking lighter alternative materials has become a major trend in the aerospace field. As an emerging material, composite materials have quickly occupied a place in the aerospace manufacturing industry with their high strength, light weight and design flexibility.
The main goal of this paper is to explore the application of composite materials in aircraft manufacturing, analyze their contribution to the lightweight design of aircraft, and possible future development directions in the aerospace field.
Overview of Composite Materials
Composites are a new type of material that combines two or more different materials to give full play to their respective advantages. Its main feature is that it can significantly improve the mechanical properties of materials, such as strength, stiffness and durability, while maintaining a low weight. The application of this material has been widely penetrated into various fields such as aerospace, automobiles, construction and sporting goods, especially in the aerospace industry, which has strict requirements for lightweight and high strength.
The structure of a composite material usually consists of two parts: matrix material and reinforcement material. The main function of the matrix material is to fix the reinforcement material in place and protect the reinforcement material under external forces. The reinforcement material provides most of the mechanical properties of the composite material.
Matrix material: The matrix material is the “glue” of the composite material, which can be a polymer, metal or ceramic. Polymer matrix materials (such as epoxy resin, phenolic resin, etc.) have become the most commonly used matrix materials in the aerospace industry due to their light weight, corrosion resistance and easy processing. Metal matrix materials (such as aluminum matrix, magnesium matrix, etc.) perform well in applications that require high temperature performance. Ceramic matrix materials have high temperature stability and wear resistance, suitable for applications in extreme environments.
Composite material manufacturing process
The composite material manufacturing process is an important factor in determining the performance and cost of composite materials. Different manufacturing processes are suitable for different composite material types and application requirements. The following are several major composite material manufacturing processes: fiber prepreg process, liquid molding process (including resin transfer molding (RTM), resin film injection (RFI) and vacuum assisted resin injection (VARI)), autoclave molding and pultrusion technology.
Fiber prepreg process
Fiber prepreg process (Prepreg) refers to the method of pre-impregnating fiber reinforcement materials (such as carbon fiber or glass fiber) in a resin matrix, and then obtaining a composite material by cold storage and heating curing. This process is widely used in the aerospace industry, especially for the manufacture of high-performance structural parts.
Process steps:
- Fiber pretreatment: The carbon fiber or glass fiber is surface treated to improve the bonding performance between the fiber and the resin.
- Impregnation with resin: The fiber is immersed in the liquid resin through the impregnation device to make the fiber evenly impregnated with resin.
- Preforming and refrigerated storage: The impregnated fiber is initially cured at room temperature or low temperature, and then stored in a low temperature environment to prevent the resin from curing prematurely before use.
Lamination and curing: The prepreg fibers are laid according to the designed number of layers and direction, and cured under high temperature and high pressure to form the final composite parts.
Liquid molding process
Liquid molding processes include resin transfer molding (RTM), resin film injection (RFI) and vacuum assisted resin injection (VARI). These processes are widely used to manufacture large and complex composite structural parts by injecting liquid resin into dry fiber reinforcement materials and then curing and molding.
1.Resin transfer molding (RTM) process steps:
- Mold preparation: Place the dry fiber preform in the mold.
- Resin injection: Inject liquid resin into the fiber preform in the mold by pressure so that the resin completely penetrates the fiber.
- Curing and demoulding: Curing the resin under heating conditions, and then removing the cured composite parts from the mold.
2.Resin film injection (RFI) process steps:
- Preform preparation: Place the fiber preform in the mold and cover it with a layer of resin film.
- Heating and curing: Under the action of heat and pressure, the resin film melts and penetrates into the fiber to complete the impregnation and curing process.
3.Vacuum Assisted Resin Infusion (VARI) process steps:
- Mold preparation: Place the dry fiber preform in the mold and cover it with a vacuum bag.
- Vacuum suction: Liquid resin is introduced into the mold through vacuum suction to make the resin saturate the fiber.
- Curing and demoulding: The resin is cured under heating conditions, and then the cured composite part is removed from the mold.
Automated Tape Laying and Automated Fiber Placement Technology
Automated Tape Laying (ATL) and Automated Fiber Placement (AFP) technologies are advanced manufacturing processes for manufacturing complex shapes and large-size composite structural parts. They use computer-controlled automatic equipment to accurately lay prepreg tapes or fibers according to the designed path, and are widely used in the manufacture of wings, fuselages and other key structural components in the aerospace industry.
Process steps:
- Material preparation: Prepreg tape rolls/fiber filament rolls are prepared and installed on the laying equipment.
- Automatic laying: The prepreg tape is laid on the mold surface according to the designed path and angle through computer control.
- Lamination and curing: After all layers are laid, they are cured by hot pressing or hot air.
Autoclave Molding
Autoclave Molding is a process in which prepreg fiber composites are placed in a mold and cured by applying high temperature and high pressure in an autoclave. This process is widely used in the manufacture of high-performance and high-demand aerospace composite parts.
Process steps:
- Material preparation: Lay the prepreg fiber material in the mold according to the design requirements.
- Vacuum bag sealing: Cover the laid material with a layer of vacuum bag and evacuate to remove the air.
- Autoclave curing: Place the mold in the autoclave and cure it under high temperature and high pressure to ensure that the resin is fully penetrated and cured.
- Demolding and post-processing: After curing, remove the finished part from the mold and perform necessary post-processing (such as trimming and coating, etc.)
Main types of composite materials
Carbon fiber composites (CFRP)
Carbon fiber composites are composite materials composed of carbon fiber as reinforcement material and polymer as matrix material. This material has been widely used in the aerospace industry for its excellent performance.
Advantages:
- High strength/weight ratio: Carbon fiber is 10 times stronger than steel and weighs only one-fourth of steel, which greatly improves the strength and stiffness of structural components while reducing weight.
- Corrosion resistance: Carbon fiber has good chemical resistance and can maintain performance under harsh environmental conditions.
- Low thermal expansion coefficient: Carbon fiber composites have a very low thermal expansion coefficient and can maintain stable dimensions in environments with large temperature changes.
Application: In aircraft manufacturing, carbon fiber composites are widely used in fuselages, wings, tails and internal structures. For example, the fuselages and wings of Boeing 787 Dreamliner and Airbus A350 series aircraft use a large amount of carbon fiber composites.
Fiberglass composites
Fiberglass composites are composed of fiberglass and a polymer matrix. Although the strength and stiffness of glass fiber composites are not as good as those of carbon fiber composites, they are relatively cheap and have simple manufacturing processes, and are still one of the important composite materials in the aerospace industry.
Advantages:
- Low cost: Fiberglass is inexpensive compared to carbon fiber and is suitable for cost-sensitive applications.
- Good impact resistance: Fiberglass has good impact resistance and can maintain good structural integrity under impact loads.
- Chemical corrosion resistance: Fiberglass has good chemical corrosion resistance and is suitable for applications in harsh environments.
Application: Fiberglass composites are often used in secondary structures and interior parts of aircraft, such as cabin walls, floors and seats. Its impact resistance and chemical corrosion resistance make it particularly widely used in these areas.
Aramid fiber composite material (AFRP)
Advantages:
- High toughness: Aramid fiber is known for its excellent toughness and impact resistance, and can maintain structural integrity under high impact loads.
- Heat resistance and wear resistance: Aramid fiber has good heat resistance and wear resistance, and is suitable for high temperature and wear environments.
Application: Aramid fiber composites are often used in bulletproof panels, cabin interiors and other parts of aircraft that require high impact resistance.
Nanocomposites
Advantages:
Ultra-high strength-to-weight ratio: Nanoscale reinforcements such as carbon nanotubes and graphene can significantly increase the strength and stiffness of composites while keeping weight very low.
Versatility: Nanocomposites can be designed to have a variety of functions, such as self-healing, sensing, and conductivity.Applications: Although the use of nanocomposites in the aerospace industry is still in the research stage, their potential applications are broad, and breakthroughs may be made in ultra-light structural components, high-performance coatings, and smart materials in the future.
Future development trend of composite materials
As a high-performance material, composite materials have broad prospects for future development. This article will discuss in detail the future development trend of composite materials from four aspects: new materials and applications, innovation of manufacturing processes, economic analysis of large-scale applications, and environmental protection and sustainable development.
With the advancement of materials science, new composite materials continue to emerge, promoting their application and performance improvement in more fields.
- Ceramic matrix composites (CMCs): Ceramic matrix composites have excellent high-temperature performance and corrosion resistance, and are suitable for the manufacture of aerospace engine blades and high-temperature structural parts. Future research will focus on improving their toughness and fatigue resistance and expanding their application range in extreme environments.
- Thermoplastic composites: Compared with thermosetting composites, thermoplastic composites have the characteristics of repeatable processing and high impact toughness. The development of new high-temperature thermoplastic resins makes it possible to use thermoplastic composites in high-temperature environments, especially in the aerospace and automotive industries.
- Smart materials: including self-healing composites, shape memory composites and sensor composites. These materials can self-repair damage, respond to environmental changes or provide real-time structural health monitoring, and are widely used in aerospace, civil engineering and biomedical fields.
Innovation in composite manufacturing processes is the key to promoting their application and performance improvement.
- Continuous fiber reinforced 3D printing: Directly manufacturing continuous fiber reinforced composite parts through 3D printing technology can achieve high-performance parts with complex shapes and optimized structures. Additive manufacturing technology not only improves material utilization, but also shortens production cycles and reduces production costs.
- Hybrid manufacturing technology: Combining additive manufacturing with traditional manufacturing processes such as CNC machining and injection molding to achieve efficient manufacturing of complex parts. In the future, hybrid manufacturing technology will be more widely used in the aerospace and automotive industries, promoting the development of personalized and small-batch production.
- Digital twin technology: By creating digital models of physical parts, real-time monitoring and optimization of the manufacturing process can be achieved. Digital twin technology can predict and analyze problems in the manufacturing process, improve manufacturing quality and efficiency, and is especially important in the manufacture of large composite structures such as aerospace and wind turbine blades.
The large-scale application of composite materials requires not only technological breakthroughs, but also economic guarantees.
- Material cost reduction: With the advancement of production technology and the play of scale effect, the production cost of carbon fiber, glass fiber and high-performance resin is expected to be further reduced. For example, the development of large-scale production processes and the optimization of raw material supply chains will significantly reduce the cost of carbon fiber and enable it to be used in more fields.
- Manufacturing cost optimization: Through the application of automation and intelligent manufacturing technology, production efficiency is improved and labor and time costs are reduced. The popularization of automated tape and wire laying equipment and the development of additive manufacturing technology will promote the efficient manufacturing of composite parts.
The environmental protection and sustainable development of composite materials are important directions for future research and application.
- Bio-based composite materials: Composite materials made of natural fibers (such as hemp, flax and sisal) and bio-based resins are not only renewable but also environmentally friendly. In the future, bio-based composite materials will be more widely used in packaging, construction, and automotive interiors, promoting the development of green materials.
- Degradable composite materials: Research and develop composite materials that can be degraded under specific conditions to reduce environmental pollution. Degradable composite materials have important application prospects in medical devices, packaging, and agriculture.
- Green manufacturing process: Develop low-energy consumption and low-emission manufacturing processes, such as room temperature curing resins, solvent-free resins, and low-temperature sintering technology. In the future, green manufacturing processes will further reduce energy consumption and environmental pollution in the production of composite materials and promote sustainable development.
In Conclusion
The future development trend of composite materials covers the progress of materials science, innovation of manufacturing processes, economy of large-scale applications, and environmental protection and sustainable development. The research and development and application of new materials will further expand the performance and application areas of composite materials; the innovation of manufacturing processes will improve production efficiency and product quality; the analysis and optimization of economic efficiency will promote the large-scale application of composite materials; and environmental protection and sustainable development are important guarantees for the healthy development of the composite materials industry in the future.
Through multi-faceted coordinated development, composite materials will play an increasingly important role in aerospace, automobiles, construction and other fields, and make positive contributions to human scientific and technological progress and green development.
