A major reason for aircraft such as the Boeing 787 Dreamliner or Airbus A350, apparently, is their use of composite materials – up to 40% of the airframe, if I recall correctly.
Is there a reason why an aircraft cannot be 70% or 80% made up of carbon composites? In theory, such an aircraft would be even lighter, and more fuel-efficient.
The B787′s structure, the wings and its fuselage is mainly composed of composite materials. The craft will be 80% composite BY VOLUME (note the difference in use of the word by volume and percentage). Each 787 contains approximately 35 short tons of carbon fiber reinforced plastic, made with 23 tons of carbon fiber.
http://www.industryweek.com/articles/boeing_787_a_matter_of_materials_–_special_report_anatomy_of_a_supply_chain_15339.aspx
This technically makes the 787 the first composite airliner in production. The 777 has about 50% aluminum & 12% composites but the 787 uses more than 50% composite (mostly carbon fiber reinforced plastic), and the rest are 15% other materials with aluminum. Also in the assembly stage, the 787 body was assembled in one piece composite barrel sections, a departure from previous assembly work
The major reason why the 787 cannot be made almost entirely of composites is too technical to explain here, but generally using a composite fuselage has not been fully assessed, according to some wary aeronautical experts. Carbon fiber, unlike metal, does not visibly show cracks and fatigue. Airbus’s 350 is using panels made of composites on a frame. This is a more normal assembly system. Airbus seems satisfied that its sub companies agree with it that this is a less risky approach than Boeing’s application of composite barrels. Another concern seems to be the property of composite materials, which can be porous, allowing them to absorb unwanted moisture. As the 787 reaches its operating height, it is generally well known that moisture expands. This may cause delamination of the composite materials resulting in weakness of a structural nature. But Boeing has dismissed these claims, though they know what they’re doing and aware of the limitations of composite materials
(Composite material delamination is too complex to discuss here, inc. metal matrix composites or MMC. Ceramic matrix composites are also in development (Cermets) E-mail me if you are interested)
One other concern that has been raised is the risk of lightning strikes. Because the 787′s body is composite, it is more resitant to electrical resistance thatn aluminium therby increasing the risk of damage during a lightning strike. But Boeing has also been up to it and said that the 787′s lightning protection will meet FAA requirements.
http://seattletimes.nwsource.com/html/boeingaerospace/2003889663_boeing180.html
However, the FAA seems to have relaxed some lightning strike requirements. (Don’t take my word for this as this still needs verification, and up to what extent…I am not aware of yet.)
only certain parts can be made from composites. IE carbon fiber cannot be used in wiring.
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In addition to what the other person said, cost is another reason. My understanding is that it costs a lot more to make a plane out of carbon fiber, regardless of fuel economy.
There also might be maintenance issues that present with carbon composite bodied planes, but I can’t say for sure. It’s at least more complex with carbon fiber.
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the biggest reason that I have been told that most commercial planes are not largely composite is because of the wiring system. Composites are non-conductors of electricity, and every electrical part on the plane would need double the normal amount of wires to allow for a ground path back to source. Metal airplanes (aluminum mostly, some steel and magnesium) allow for the airplane structure to be the electrical ground path.
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The B787′s structure, the wings and its fuselage is mainly composed of composite materials. The craft will be 80% composite BY VOLUME (note the difference in use of the word by volume and percentage). Each 787 contains approximately 35 short tons of carbon fiber reinforced plastic, made with 23 tons of carbon fiber.
http://www.industryweek.com/articles/boeing_787_a_matter_of_materials_–_special_report_anatomy_of_a_supply_chain_15339.aspx
This technically makes the 787 the first composite airliner in production. The 777 has about 50% aluminum & 12% composites but the 787 uses more than 50% composite (mostly carbon fiber reinforced plastic), and the rest are 15% other materials with aluminum. Also in the assembly stage, the 787 body was assembled in one piece composite barrel sections, a departure from previous assembly work
The major reason why the 787 cannot be made almost entirely of composites is too technical to explain here, but generally using a composite fuselage has not been fully assessed, according to some wary aeronautical experts. Carbon fiber, unlike metal, does not visibly show cracks and fatigue. Airbus’s 350 is using panels made of composites on a frame. This is a more normal assembly system. Airbus seems satisfied that its sub companies agree with it that this is a less risky approach than Boeing’s application of composite barrels. Another concern seems to be the property of composite materials, which can be porous, allowing them to absorb unwanted moisture. As the 787 reaches its operating height, it is generally well known that moisture expands. This may cause delamination of the composite materials resulting in weakness of a structural nature. But Boeing has dismissed these claims, though they know what they’re doing and aware of the limitations of composite materials
(Composite material delamination is too complex to discuss here, inc. metal matrix composites or MMC. Ceramic matrix composites are also in development (Cermets) E-mail me if you are interested)
One other concern that has been raised is the risk of lightning strikes. Because the 787′s body is composite, it is more resitant to electrical resistance thatn aluminium therby increasing the risk of damage during a lightning strike. But Boeing has also been up to it and said that the 787′s lightning protection will meet FAA requirements.
http://seattletimes.nwsource.com/html/boeingaerospace/2003889663_boeing180.html
However, the FAA seems to have relaxed some lightning strike requirements. (Don’t take my word for this as this still needs verification, and up to what extent…I am not aware of yet.)
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B.S. Aeronautical Eng.
Because they need to be strong enough to fly.
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