Ultrasonic waves can find bubbles and cracks in adhesive bonds holding airplane composite parts together, and now aerospace engineers can select the best frequencies to detect adhesive failures in hard-to-reach places more quickly, thanks to Penn State researchers.

Different ultrasonic modes work best for different materials and configurations using the right one will locate more flaws with higher precision, according to the researchers. The selection process could save time and effort for engineers who perform maintenance on complex structures made from composite materials -- like airplanes.

Adhesive bonds are better for attaching composite parts than nuts and bolts, which pierce and weaken structural integrity. But heavy operation can crack the glue, damaging the bond's effectiveness. Ultrasonic waves let engineers examine bonded regions without having to dismantle anything.

"This technique is very widely used in aerospace engineering because those structures require a very high reliability," said Baiyang Ren, postgraduate in engineering science and mechanics. "When something like an airplane or helicopter, bridge, ship has some component that fails suddenly, that could cause a severe accident."

Penn State’s Applied Research Lab (ARL) and the Department of Engineering Science and Mechanics’ (ESM) Composite Manufacturing Technology Center (Composite Lab) provided key support to the Penn State Racing team this past school year. Professors Tom Juska of ARL and Chuck Bakis of ESM guided the team as they prepared for the annual Formula Society of Automotive Engineers (FSAE) competition in May. The student-run group was tasked with designing and prototyping a formula-style race car for the competition.

Held at the Michigan International Speedway, the FSAE competition hosted 120 teams from across the globe that were judged on a variety of factors, including production cost, fuel economy, and a grueling endurance race. Penn State’s team was one of 19 competitors with a winged aero-package. This design included composite carbon-fiber front and rear wings and side pods and the car ranked competitively in many categories.

During a recent visit to campus, Congressman Glenn Thompson toured the College of Engineering’s Learning Factory, where the FSAE car is housed. ESM senior and FSAE team member Shawn Liang presented the car to Representative Thompson and described the students’ hands-on learning experience readying the car for competition.