Mechanical engineer learns from failure

Anette Karlsson is not afraid of failure. In fact, the assistant professor of mechanical engineering has built a successful research career on a foundation of failure.

“I’m interested in seeing how structures and materials fail, because that’s the only way to understand how to design better ones—ones that won’t fail,” Karlsson says. “I have two main projects right now, and in some ways they’re very different from each other because one involves hard ceramic coatings, and the other involves a soft polymer membrane.

“What the projects have in common is that they both deal with how materials fail.” Karlsson’s longer-running research project concerns the coatings placed on gas turbine engines to protect the components against the high temperatures at which such engines operate. Her newer research interest is hydrogen fuel-cell technology, in which she is exploring the reasons a thin polymer membrane in the cells breaks down over time. In both cases, her work seeks to find ways to slow the degradation of materials and extend their useful lives.

In 2004, Karlsson was one of 26 scientists nationwide who were recognized with a grant from the prestigious U.S. Office of Naval Research Young Investigators Program. Her grant of $360,000 was awarded for her work in investigating a novel approach to establishing lifetime material performance for multilayered coated structures.

“We start by conducting experiments on gas turbines, which can be stationary [in power generating plants, for example] or mobile [such as aircraft engines], to see how they fail,” Karlsson says. “From there, we develop numerical computer models to try to predict what will happen based on the thousands of cycles that a turbine goes through. You have to match the experiments with their theoretical calculations.”

If successful, she says, these numerical models eliminate the need to run experiments over and over to test the lifespan of coatings. By predicting the rate at which coatings become deformed and fail, the models also eliminate the need for a computer to do the same complex calculations repeatedly, she says.

“The coatings I work with have multiple layers, each with its own function,” Karlsson says. “To develop a model, you need to separate out the essentials. I start with a very simple model, with just one layer, and then gradually add layers and complexity.”

Right now, she says, such coatings on aircraft engines are considered a back-up system: If they’re removed, the engine still functions. The goal of her research is to design longer-lasting and more protective coatings.

Karlsson also is one of numerous researchers in the College of Engineering who are working with various aspects of hydrogen fuel cells, a technology that has the potential to create clean, economical power that does not consume fossil fuels. Automotive engines, power plants and even laptop computers might someday operate using fuel cells instead of burning gasoline or coal or using batteries, proponents of the technology say.

Hydrogen fuel cells contain plates, each made of a proton exchange membrane sandwiched between two sides of carbon. The cells take in hydrogen and air, create electricity and produce only water and heat, with no greenhouse-gas or other emissions.

In collaboration with Michael Santare, professor of mechanical engineering, Karlsson’s fuel cell research focuses on the membrane, which she says is one of several issues under investigation by scientists seeking ways to make fuel cells operate more efficiently and for longer periods of time. She adds that a combination of mechanical failure and chemical degradation leads the membrane to fail eventually.

“In our lab, we’re testing the membrane under various environmental conditions, such as different temperatures and humidity levels,” Karlsson says. “Then, we can put those factors into our model and see how and why the membrane fails.”

Karlsson joined the UD faculty in 2002. Before earning her doctorate  from Rutgers University in 1999, she worked as an engineer at Saab Aerospace in Sweden, where she also investigated materials failure in aircraft.

—Ann Manser, AS ’73, CHEP ’73