Earlier this year, on January 2, a Japan Airlines Airbus A350 landing at Haneda Airport collided with a De Havilland Canada DHC-8 Coast Guard aircraft that appeared on the runway. Both planes caught fire, and five of the Coast Guard plane’s six crew members were killed in the collision. The airliner was also completely destroyed, but surprisingly all 367 passengers and 12 crew members survived despite the extensive fire.
The circumstances in which the accident occurred are not yet known and will be clarified by further investigations. After the collision, the burning airliner continued to slide down the runway until it came to a stop. There the crew managed to evacuate all the people on board the vehicle before the flames completely engulfed the plane. However, the evacuation was successful only because the plane remained almost intact in the collision and did not crash into the mud.
First, the plane was low on fuel when it landed and this prevented a major explosion. Secondly, more than half of the Airbus A350 fuselage is made of carbon composite materials. This is still a relatively new trend in the world of aviation, and no other passenger plane contains so much carbon fiber plastic. Historically, airliners have been made predominantly of aluminum and steel. The A350 model was only introduced in 2013.
The rigid body could have been useful in an accident
Silvar Kallip, an electrochemist from the University of Tartu, who studied the corrosion of aircraft bodies and the contact of carbon materials and metals on boundary surfaces, said that carbon composite materials have long been a very hot in the aviation industry. “To put it simply, this material is made of a very strong carbon fiber fabric and a special epoxy resin that holds this reinforcement fabric together. It is mechanically very strong and rigid and at the same time lightweight,” Kallip told ERR .
The carbon composite is about 30 to 40 percent lighter than the main airframe material, AA2024-T3 aluminum alloy, while being more rigid. Therefore, CFRP (carbon fiber reinforced plastic) According to Kallip, this is a highly anticipated material in the aviation sector, because especially in civil aviation it involves large volumes. Any reduction in aircraft weight results in fuel savings and a direct reduction in carbon emissions.
“Under normal circumstances violent impacts on the airframe are not particularly expected and collisions with birds should not pose a major problem for CFRP materials. In the case of the Haneda accident, it may also be that the stiffness and lightness of the airframe, compared to a standard airframe made of aluminum, somewhat improved the stability of the aircraft in the event of a collision with a small aircraft. However, at the current stage of the investigation nothing can be said with certainty,” the electrochemist noted.
Unfortunately, CFRP also has its concerns. That is, it burns a little better than aluminum in a fire. However, according to Kallip, it is unlikely that the CFRP building material caught fire. In addition to other weak points, the associate professor highlighted the long production and processing process as well as the problematic circular management.
CFRP hulls would be easier to strengthen
Taivo Jõgiaasa, a materials scientist at the University of Tartu, is quick to conclude that CFRP played an important role in holding the fuselage together. “The stability of the one-piece fuselage does not depend so much on the material used, but rather on the thickness of the panels on the outside of the fuselage,” he pointed out.
“It is clear that it is easier to break a thin piece of board in half than a thick one. Since the dimensions of the panels on this aircraft and the force exerted on the panels in the accident are unknown, it is actually impossible to say whether the use of panels of the carbon fiber and plastic bodywork had just such an effect,” the researcher said.
However, according to Jõgiaasa, CFRP materials could definitely make aircraft bodies much stronger. “If you use a material that is, for example, five times stronger than the material used previously, the parts could be made, to put it simply, five times thinner. The finished aircraft will weigh less and fuel consumption will decrease by consequence. However, if for some reason the manufacturer decides to make a slightly thicker part with the new strong material, the strength of the structure could really increase and also the safety,” said Jõgiaas.
“Compared to metals, such an increase in strength is easier to achieve with carbon fiber composite materials, because with respect to density they are many times stronger than steel,” he added. According to Jõgiaasa, carbon fiber plastic is mainly used because parts made from it are lighter than, for example, aluminum, titanium or steel alloys, with the same strength.
“Lifting a heavy object into the air requires more energy. The latter is expressed in higher fuel consumption in the case of an airplane, which in turn leads to higher financial costs and higher ticket prices. So it is logical that the purpose main of “The materials and structures used in aviation must still reduce the weight of the aircraft. At the same time, we must not lose structural strength,” the scientist explained.
Increased fire risk
Like Kallip, Jõgiaas also highlighted a slightly higher fire risk in the case of CFRP materials. No one can yet say whether he played a role in the Haneda incident. “Most people who have seen burning plastic can already imagine what happens to such panels when they overheat,” the materials scientist said.
“The glue in the composite panel begins to break down and burn at a higher temperature. Considering that carbon fiber is a flammable material even in air, the flammability of a composite with such carbon fiber is slightly higher than that of composite panel. a normal aluminum alloy panel,” he added.
At the same time, Jõgiaas stressed that carbon fiber plastics are not flammable per se. Some kind of external heat is needed to turn them on. “Unfortunately, I don’t know what ignited first. If it was fuel, it makes sense that sooner or later the carbon structure would also ignite. If the composite structure ignited first, this could have been caused by strong friction between the parts. panel and the walkway, but it is highly speculative,” the researcher noted.
“To summarize the above, I would say that from a materials perspective this is a very interesting accident. Although there is nothing good in accidents themselves, sometimes you can learn something from them. So it would be important to know what role, or if at all, such unpublished materials actually played into such an incident. Unfortunately, no, it is likely that the reasons for this, or what exactly happened, will be discussed publicly in great detail in the future. However, I hope so ,” Jõgiaas expressed hope.
2024-01-09 04:48:00
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