Volume 8, Number 2     March/April 2000

Aeropace Technology Development

New Lab Plans to Impact Engine Design

One of the main tasks of the new ballistic impact facility at NASA’s Glenn Research Center in Cleveland, Ohio, is testing materials for aircraft engine housings. During rare in-flight events, an engine is hit by hail or birds. If this happens, the engine housing must contain any fragments and withstand the severe loads, or forces, that otherwise could cause the engine to separate from the wing of the airplane.

Current engine housing materials, usually high-strength metal alloys and non-metal ballistic fabrics, do this job very well, but are very heavy. The new, lighter structures being considered for this duty must be evaluated for their ability to withstand such catastrophic events.

The main features of the facility are a 40-foot-long gas gun that can eject projectiles at speeds up to 1,500 feet per second, or more than 1,000 miles per hour, and a high-speed camera that can capture 2.5 million images per second.

"The whole idea is to watch the impact and see how the materials struck by the projectiles behave," said Dale Hopkins, a structures engineer and team leader for the design and build-up of the new facility. "It’s not just whether they survive, but how they deform and fail."

"The new facility allows us to use larger, heavier, irregularly shaped projectiles that look and behave more like fragments of an engine’s rotating parts. The testing is much more realistic than before," Hopkins added.

The facility is also being used to evaluate flywheel containment materials. The disk in a flywheel, a new type of energy storage device being considered for use in satellites and other advanced applications, rotates at more than 50,000 revolutions per minute. If the disk fatigues and ruptures, the high-speed particles released would need to be contained to avoid damaging other equipment or injuring people.

Materials to be tested include intermetallic alloys, fiber-reinforced composites and cloth-like polymers. New engine concepts require materials that can withstand higher temperatures and higher speed projectiles than current containment materials. Similar work at Glenn more than 20 years ago helped prove the worth of the ballistic materials used in jet engines today, as well as in bullet-proof vests.

The data taken during these impact tests will also be used to verify and improve the accuracy of computer models that predict material response to impacts. Manufacturers can use these more accurate models to shorten the time and reduce the cost of bringing new designs to market.

For more information contact Lori Rachul at Glenn Research Center. 216/433-8806, lori.j.rachul@grc.nasa.gov Or contact Dale A. Hopkins at NASA Glenn Research Center. 216/433-3260, dale.a.hopkins@grc.nasa.gov Please mention you read about it in Innovation.