In this blog post, we will examine how the advancement of materials science has contributed to aircraft design and performance improvement through various material characteristics and application examples.
Airplanes are symbolic of the advancement of human science and technology. In 1906, the Wright brothers’ airplane became a symbol of the most direct advancement of human science and technology. Since the Wright brothers obtained a patent for their aircraft design in 1906, aviation technology has undergone remarkable development over more than 100 years, and now aircraft are an essential means of transportation connecting the world and a catalyst for economic and cultural exchange. Aircraft are no longer a product of special technology, but have become a familiar sight in our daily lives, crossing the sky whenever we look up. However, the sight of a massive aircraft carrying dozens or hundreds of people across the sky remains awe-inspiring. Around the world, various technological research efforts are actively underway to develop faster, safer, and more environmentally friendly aircraft. From the perspective of materials engineering, what materials are used to construct these massive flying machines, and what physical properties are required?
Before delving into the specifics of aircraft materials, it is essential to first understand the physical properties required for such materials. Above all, strength is paramount. To withstand the weight of the aircraft itself, dozens of passengers, cargo, and cabin pressure, high structural strength is indispensable. However, simply using strong materials is not the solution.
If heavy materials are used solely for strength, flight efficiency will significantly decrease, requiring larger engines and more fuel, thereby reducing economic efficiency and practicality. Therefore, materials with high “specific strength,” or strength per unit weight, are suitable for aircraft. Additionally, aircraft must endure continuous vibrations and repeated loads during flight, so they require a long fatigue life.
Wear resistance against air friction and corrosion resistance against humidity and salt are also important. Especially for supersonic aircraft or high-altitude vehicles, heat resistance is essential to maintain structural stability even at high temperatures. Additionally, machinability, weldability, and formability are critical from an industrial perspective as they influence production costs and process efficiency.
Early aircraft were primarily constructed using wood and fabric. While wood had the advantages of being lightweight and easy to process, it had limitations in terms of strength and durability. To overcome these limitations, Duralumin, developed by German metallurgist Alfred Wilm in the early 20th century, began to be adopted as an aircraft material. Duralumin is an alloy of aluminum with copper, manganese, and magnesium, which is about one-third the weight of iron but boasts high strength. It is also easy to process, making it advantageous for reducing aircraft manufacturing costs.
To this day, Duralumin and its improved versions, Super Duralumin and Super Super Duralumin, are still widely used as major aircraft structural materials. It can be found in long-range commercial aircraft such as the Boeing 737 series and the 747-400. However, duralumin has the drawbacks of reduced strength at high temperatures and susceptibility to corrosion when exposed to salt or humidity over extended periods. To address these limitations, titanium alloys (titanium alloy) are used in high-speed aircraft and components requiring heat resistance. Titanium has excellent strength, fatigue resistance, and corrosion resistance, and remains stable at high temperatures. However, it is difficult to process and expensive, so it is used only in specific areas such as outer shells and firewalls. Additionally, high-strength special steels are applied to areas subjected to heavy loads, such as bolts, gears, and landing gear.
The biggest topic in the aviation industry today is carbon fiber reinforced polymer (CFRP). Composite materials are materials that combine two or more materials to maximize the advantages of each material, typically combining a low-stiffness base material (matrix) with a high-strength reinforcement such as fibers. Carbon fiber is highly regarded as a key material for aircraft lightweighting due to its excellent specific strength and specific stiffness, while weighing only one-sixth as much as steel. Additionally, carbon fiber prevents load concentration and crack propagation when internal cracks occur, making it superior in terms of fracture resistance. Since it is not a metal, it also exhibits excellent corrosion resistance.
By applying CFRP to aircraft structural materials, weight can be significantly reduced, leading to lower fuel consumption and, ultimately, reduced carbon dioxide emissions. The Boeing 787 Dreamliner is composed of approximately 50% composite materials, with about 43% of that being carbon fiber composites. As a result, it achieved approximately a 20% reduction in fuel consumption compared to previous models and reduced the overall weight of the aircraft by over 5 tons. The Airbus A350 XWB is another representative example that achieved improved fuel efficiency and reduced carbon emissions by constructing over half of its structure using composite materials.
In addition, next-generation aircraft materials such as ceramic fiber composite materials (CMC), conductive coating composites, and nanoparticle-reinforced composite materials are being actively researched. For example, silica nanoparticles are being added to improve heat resistance and wear resistance, and conductive material coating technology for lightning protection is also being advanced.
These new material technologies have great potential for application in supersonic aircraft, high-altitude unmanned aerial vehicles (UAVs), and personal eVTOL aircraft. Beyond the aviation field, high-strength, low-weight composite material technology is already expanding into various fields such as automobiles, railways, space, and defense industries.
Recently, global automakers such as BMW, Tesla, and Lucid Motors are designing the bodies of high-end electric vehicles using carbon fiber composites to achieve both weight reduction and improved driving range. In the aerospace sector, space agencies around the world, including NASA, ESA, and Japan’s JAXA, are increasingly adopting CFRP-based materials for rocket, satellite, and spacesuit components.
Furthermore, with the emergence of next-generation eco-friendly aircraft such as electric aircraft and hydrogen fuel aircraft in the mid-2020s, research on ultra-lightweight, high-performance materials that will enable these aircraft is becoming increasingly active.
In the future, demand for air transportation is expected to increase in various forms, including passenger, cargo, military, unmanned aircraft, and eVTOL. As a result, aircraft materials will continue to evolve toward being lighter, stronger, safer, and more environmentally friendly. Next-generation aircraft materials, including carbon fiber-reinforced composite materials, are emerging as core elements driving the sustainable future of the aviation industry, transcending their role as mere structural materials. The advancement of such material technologies holds the potential to not only improve aircraft performance but also provide solutions to humanity’s mobility challenges and environmental issues.
