Making Carbon Fiber Conductive for Aerospace Applications

Making Carbon Fiber Conductive for Aerospace Applications

Aerospace giants like Boeing and Airbus are among the largest consumers of composite materials in the world. They utilize a variety of materials from glass fiber to carbon fiber for manufacturing everything from fuselage panels to seats. The strength-to-weight ratio of these composite materials is what allows manufacturers to continue building larger aircraft still capable of flying.

Now there is a new effort afoot, an effort to make largely composite airplanes more conductive to electricity. Why? To protect the aircraft from lightning strikes. The fact is that airplanes are routinely subject to lightning strikes as a matter of course. The problem with materials like carbon fiber is that they aren't very conductive.

A conductive material is a material that is capable of conducting, or transmitting, heat or electricity. For the purposes of this discussion, conductivity is the ability to transmit electricity from one location to the next. The outer skin of an airplane needs to be able to conduct electricity so as to dissipate it in the event of a lightning strike.

HOW THEY DO IT NOW

Modern aircraft can be built with structures containing up to 40% composite materials. As previously mentioned, fuselage panels are often made of carbon fiber. Managing lightning strikes with so much composite material requires using other materials that are more conductive.

The solution to lightning strikes right now is to combine carbon fiber structures with other components capable of conducting electricity. Engineers will build embedded wires, foils, and mesh systems into their planes in strategic locations. The solution works well enough, but it is not ideal.

These metal systems are subject to corrosion. Second, because they are built into a plane's carbon fiber air frame, they can be difficult service. An ideal solution would be to replace the metal components with a composite material that is inherently conductive by itself.

LOOKING AT HYBRID MATERIAL

A group of Chinese researchers studying the problem may have come up with a solution involving a hybrid product. The product, a nickel-coated carbon fiber veil, is already in use as a shield against electromagnetic interference. The researchers used the veil as a base for producing a standard carbon fiber reinforced plastic (CFRP). It was tested alongside a second CFRP with a copper foil mesh.

The researchers then tested their two composite materials by simulating a large section of the aircraft structure known in the aerospace industry as zone 2. This zone covers most of a commercial aircraft's air frame. Both materials were subject to dual waveforms of artificial lightning that simulated lightning strikes in the air.

Testing revealed that samples made with the veil performed better than the samples utilizing the copper mesh alone. This led researchers to conclude that a hybrid composite air frame would perform better during lightning storms than some of the systems currently being used.

MAKING IT VIABLE

Utilizing a hybrid material may be the way to go to improve conductivity in modern aircraft. However, it is too soon to know for sure if the material developed by the Chinese researchers represents the best way to attack the problem. The next step would be taking their hybrid and ramping it up for full-scale tests.

It is one thing to test a hybrid composite in the lab. Making it a viable material for widespread commercial use is an entirely different matter altogether. The good news is that science seems to be on the right track. By looking to create a hybrid product rather than continuing to rely on current systems in perpetuity, the industry is demonstrating its commitment to improving composites for the future.

Sources: Science Direct – https://www.sciencedirect.com/science/article/pii/S02663538183

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