How do composite fuselages (i.e. Airbus A350 & Boeing 787) deal with lightning strikes?
As I have mentioned in previous answers, lightning strikes are generally quite harmless to airplanes. Even if there is a direct strike, it would not penetrate the cabin; affect the engines or the fuel tanks. When an airplane is struck by lightning, the electrical charges simply travel the length of the aircraft and exit harmlessly through the antenna-like rods at the trailing edges of the flaps or, tail of a plane.
The strike, however, may cause some burn marks on the fuselage skin at the point of impact. The pilot would normally be aware of such a strike and report this incident to the engineers after landing for further inspection and rectification if necessary.
However, with more composite materials being used in planes such as the Airbus A350 and Boeing 787, questions such as yours are increasingly being raised as to how they would take lightning strikes as opposed to the conventional aluminium frames as used in non composite planes.
Researchers found that aluminium behaves better than composite materials.
This is because aluminium is a good conductor of electricity and any powerful strikes were quickly dissipated. Experiments showed that when lightning struck the carbon composite, it didn’t perform as well. This is because carbon-composite materials have far higher electrical resistance than aluminium.
It is the same property which causes electric heaters and light bulbs to become hot when electricity is applied. It will be the integrity of this material which keeps all such aircraft flying.
Engineers proposed several ways of protecting the composites, such as having a layer of metal mesh or thin foil on the top, but this increases the overall weight and means that both the coating and the composite get damaged during rectification. This would make the repair procedure even more complicated on such planes. Dexmet (see video below) has come up with a lightning strike protection for composites with this ‘butt splice application’ to resist damage to the aircraft skin.
Meanwhile, the latest Airbus A350 has just completed the lightning strike tests. Airbus developed a solution where “metallic foils are embedded in the aircraft’s composite panels – increasing the electrical conductivity and protecting harnesses with metallic conduits.”
According to the Boeing 787 website, the entire fuselage, including the skin, formers, and stringers, and the wing of the 787 are made of composites. Their solution – using a wire mesh laminated into the composite parts to provide conductivity so as to dissipate electricity better.
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