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Engineering Prof Studying Effects of Lightning Strikes on Passenger Planes

Planes get struck by lightning an average of once a year. It's a byproduct of today's packed flight schedules, where it's simply not possible to send most flights the long way around a storm front.

Passenger airplanes used to be made almost exclusively of aluminum or other metals, and aviation experts could predict how a highly charged bolt of lightning would travel through the fuselage after a strike.

But what happens when the body of these passenger jets is made increasingly from plastic composite materials?

Old Dominion University researchers have received a grant from the National Institute for Aerospace (NIA) to test samples of these materials, to see how the damage that might occur is related to the detailed current flow through the materials - and repeated exposure.

Wes Lawrence, an assistant professor of electrical engineering technology in the Batten College of Engineering and Technology, said airplanes have built-in protection from lightning strikes. Even a plane with a fuselage that's largely made of plastic composite material will have protective measures to safely channel away the majority of current flow from a strike.

"The research we're interested in is this: What if lightning attaches itself to an airplane? Even if the majority of the current flow is through the protective measures on the outside skin of the craft, there's still a moderate current that would be induced inside the structure," Lawrence said.

"So we asked the questions: Is there a cumulative effect? Are 10 lightning strikes with a current one-tenth the damage threshold an issue? Or is it simply a threshold?"

With a $16,000 seed grant from the NIA, Lawrence and Ramamurthy Prabhakaran, eminent professor in ODU's Department of Mechanical and Aerospace Engineering, are working with graduate student James Meadows to create an electrical model for the current flow through a piece of plastic composite, such as one that would be used on the outside of a plane.

"We're exposing various (pieces of the plastic composite) to these moderate currents, and then trying to determine how much energy is deposited through the structure," Lawrence said.

The electricity being sent through the samples is low compared to a lightning strike, because of the protective measures. But Lawrence wants to see if the material strength is affected by exposure, and then by repeated exposure.

The researchers will first expose some pristine samples to electrical current to get a baseline of how strong the materials are. "Then we'll expose them to currents that most people would argue wouldn't have any effect," Lawrence said. "Our point of view is that this still may be enough to cause damage to the fibers."

Lawrence said considerable research is being undertaken by the NIA and others to study the effects of lightning strikes on advanced composite aircraft to ensure continued safety of the vehicle.

The next step in the research is to try to improve the model to predict damage, and then create sensors to monitor it, Lawrence said.

"If we understand the details of how these moderate currents can potentially damage the structure, then maybe we could create several current-measuring models on the surface of the aircraft, so that when it gets struck by lightning, we can help determine whether or not there was damage," Lawrence said.

This article was posted on: June 7, 2011

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