As the cornerstone of the aviation industry, materials have played an important role in the development of aviation for a century. Today, with the increasing requirements of humans for flight speed and comfort, and the increasingly stringent requirements of operators for aircraft efficiency, manufacturers are constantly trying to use new materials and new processes to improve aircraft performance to better meet all parties Requirements.
From bamboo fiber to spider silk
Although composite materials have obvious advantages compared to traditional metal materials, in the context of "green aviation", this material has its inherent weaknesses-during the production process, composite materials are difficult to cure after curing. Decompose and recycle again. Therefore, the waste of carbon fiber composite materials can only be disposed of by landfill, which has caused some impact on the environment.
To solve this problem, a number of French companies are jointly conducting a project called "BAMCO", which aims to develop a new type of bio-based composite material made of bamboo fiber. This more environmentally friendly composite material can be used to replace glass and phenolic resin-based composite materials in the future, and is used in aircraft cabin interior covers, fuselage covering covers, and onboard kitchens.
Multiple test data show that bamboo fiber is lighter than traditional glass fiber but has a considerable level of stress, which makes it ideal for "non-bearing or sub-bearing structures with simple geometric shapes inside the cabin" alternatives.
In order to reduce production and use costs, in the BAMCO project, the development team combined this biomaterial-based composite material with traditional manufacturing processes, which will play a key role in the mass production of materials. At present, some European cabin and component manufacturers have shown great interest in this new material. According to publicly available data, Lisa Europe will be the first customer in the world to use cockpit components made from new bio-based composites.
At the same time, Airbus is cooperating with German AMSilk company to jointly develop a new composite material made of synthetic spider silk fibers, and plans to release products made of this new material this year.
This new type of composite material made of synthetic spider silk fibers is called "biosteel" and is a new material derived from a scientific research result of the Technical University of Munich. Simply put, this new material is a biopolymer material made from spider silk protein. Researchers use bacterial fermentation embedded in spider genes to obtain this protein and apply it to commercial applications.
At present, this material has been applied to some of Adidas' sports shoes, which has lighter weight and better shock absorption. Inspired by this, Airbus is working with AMSilk to accelerate the development of this new material. If it goes well, Airbus will be the first aviation company in the world to use this "biosteel".
Boeing is not far behind in the development of new materials. Currently, Boeing is working with HRL Labs and the University of California, Irvine to develop an ultralight metal material that is 100 times lighter than foam plastic.
This kind of material called "microlattice" (99.99%) is a hollow structure, that is, 99.99% is air, and the remaining 0.01% is a 3D porous polymer hollow tube connected to each other. One thousandth of the wire diameter.
According to the Boeing Company, if an egg is wrapped in this material and dropped from the 25th floor, the egg will not be damaged in any way. The hollow porous structure makes it have super high energy absorption characteristics, even if the body is compressed by 50 It can also be easily restored after%.
In addition, this new material is 100 times lighter than foam and is similar to the structure of bones. In a video published by Boeing, researchers can easily blow up the microlattice metal, which floats gently into the air like a feather and then slowly falls to the ground. It is difficult to imagine this as a metal material. Boeing said that if this material can be used in aircraft manufacturing, it will greatly reduce the weight of the aircraft and achieve higher fuel efficiency.
In addition to the development of new materials, NASA's research team is also "whimsical" trying to use the structure and molecular arrangement of the composite itself to improve the efficiency of the wing.
Aerodynamic studies have shown that the shape of the wing has a huge impact on flight efficiency. In theory, the design of the wing depends on many factors, such as the weight of the aircraft, the speed of the flight, and the attitude of the aircraft. From this perspective, rigid wings are not the most efficient wings. To this end, NASA's adaptive digital composite aviation structural technology team uses carbon fiber composite materials to design wings that can change shape during flight to reduce flight resistance.
In this study, NASA worked with the Massachusetts Institute of Technology, Cornell University, UC Santa Cruz, UC Berkeley, and UC Davis to use new composite materials To make an ultralight wing that can actively change shape.
In this NASA study, the wing is composed of carbon fiber composite building blocks. These component units are assembled into a lattice structure or arranged in a repeating structure. The arrangement of the components determines the way the wing is bent. With the help of brakes and flight control systems, the wings can become the most suitable form in different flight conditions.
NASA said that the most significant feature of this more intelligent wing is that it can improve the aerodynamic efficiency of the aircraft by reducing the drag caused by rigid control surfaces such as flaps, rudders and ailerons.
Innovative production technology came into being
According to a market forecast report issued by the International Air Transport Association (IATA), global airlines carried 4.3 billion passengers in 2018, and by 2037, this number will increase to 8.2 billion. To meet the rapid development of air transport, aircraft manufacturers will need to deliver at least 36,700 new aircraft over the next 20 years.
In order to meet the demand for capacity increase, some innovative production processes have emerged. Among them, the entry of the non-autoclave process into the manufacturing field of the main bearing structure of thermoset composite materials has triggered a revolution in the composite material manufacturing system. Since the use of autoclave is expensive and it also limits production efficiency, getting rid of the constraints of autoclave is the key to reducing costs and increasing efficiency in the production of composite materials.
In 2015, NASA began its first attempt. It tested a non-cylindrical composite pressure chamber verification piece for a wing-body hybrid aircraft, which used Boeing's non-autoclave tank manufacturing process. In April of the same year, Aeroflot Composites delivered the first set of composite central wing boxes manufactured by the non-autoclaved tank process of the MC-21 mainline passenger aircraft. This technology is used for the first time in civil airliners.
With the support of the manufacturing process, thermoplastic materials have begun to gradually replace thermoset materials, and are increasingly used in aircraft load-bearing components.
Airbus said that before the A350 project, the company had applied thermoplastic materials to more than 1,500 parts. In addition, under the EU's framework plan, Airbus is also accelerating research on the main bearing structure of large thermoplastic composites.
Bombardier has unveiled a new thermoplastic composite bracket technology suitable for hydraulic and fuel brackets of aircraft wings, central wing boxes and fuel tanks. Parts made with this new material can reduce weight by at least compared to metal materials. 40%.
With the maturity of technology and lower costs, more manufacturers of composite structural components will choose non-autoclave materials and processes from the perspective of economics and short cycles. A new revolution has been initiated in the equipment supply chain, and more and more companies have participated in this technological change.
U.S.-based Tri-Mack Plastic Manufacturing offers a "hybrid" thermoplastic composite part in which a unidirectional fiber-reinforced thermoplastic composite (for strength and stiffness) is combined with an injection molding process to achieve design flexibility. Rigid unidirectional carbon fiber will hinder the production of parts into various complex shapes, and injection molding brings additional functions to the part, and overcomes the challenge of poor processability caused by rigid unidirectional carbon fiber.
Tri-Mack says the entire process is fully automated and has shorter cycle times than manufacturing thermoset composite parts with the same performance.
In addition, some manufacturers have taken a different approach and increased production efficiency by developing 3D "weaving" technology for composite fibers.
French manufacturer Saint-Gobain has developed a 3D "weaving" technology for composite fibers that combines the weaving of thermoplastic resin fibers with reinforced carbon fibers. When the part is cured, the thermoplastic resin becomes the matrix of the material, and carbon fibers are embedded in it. At present, business jet maker Dassault has used components produced by this process on a Falcon business jet.
According to Saint-Gobain's plan, this process will also be extended to the manufacture of radomes, propeller hubs and exhaust fairings in the future.