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Material Research

Posted by on Wednesday, October 12, 2011 in Fall 2011, Next.

Çağlar Oskay is an expert in failure and that makes him—and his work—a success. Oskay, assistant professor in the Department of Civil and Environmental Engineering since 2006, has focused much of his research on the failure of structures and predicting the lifespan of heterogeneous materials through multiscale computational mechanics.

“People have started looking into materials, not from a ‘this is what God gave us and this is what we have to do’ perspective, but from a design perspective,” Oskay says. “With nanotechnology, we can look at materials as a way of engineering the materials rather than just using the materials. These developments are pushing the multiscale boundaries.” His area of engineering, Oskay explains, involves the development and use of computer simulation technologies to understand the mechanical behavior of advanced materials and structures.

Pushing boundaries is familiar territory for Oskay, who is valued by the U.S. Air Force for his drive to ensure real-world applications for his research. “Academicians by and large will develop methods and models and apply them to simple configurations to demonstrate that they work,” says Ravi Chona, director of the Structural Sciences Center at the Air Force Research Laboratory, Wright-Patterson Air Force Base in Ohio. “Rarely are they willing to get into the issues of real applications. Çağlar doesn’t shy away from that, which is very, very good from my perspective. What he’s trying to do is absolutely integral to the basic research efforts we have in-house.”

Failure is Important

Two of Oskay’s main areas of research are applicable to materials used in military aircraft, which are consistently being reconfigured to fly farther and faster. Using computer models, Oskay attempts to predict when materials might fail under extreme conditions, such as high heat and traveling at extremely high rates of speed. Another area studies failure rates of complex composite materials.

Pipes made of modern composite materials might prevent pipeline ruptures such as this one in Michigan.

Oskay says research of the past 50 to 70 years has revealed how traditional materials fail, allowing solutions to be found, but that today’s advanced materials still need research.

“There have been many, many different composite materials invented, and we don’t know how they fail, in what way they fail, and how to model their failure,” he says. “What we’re trying to come up with is computational strategies that can be used to model and assimilate the failures.”

This has become increasingly important, not just to the military, but also to the flying public. The new Airbus A350, due to be delivered to airlines in 2013, is expected to use more than 50 percent composite materials, including in portions of the wings and fuselage. Such composite materials hold the possibility that they might prevent corrosion and aging issues associated with all-metal aircraft; being lighter, they could increase cargo capacities, improve aircraft performance and lower operating costs.

“What he’s trying to do is absolutely integral to the basic research efforts
we have in-house.”

— Ravi Chona, director, Structural Sciences Center, Air Force Research Laboratory, Wright-Patterson Air Force Base

“When composite materials first were introduced as structural components, designers and engineers were using such high safety factors that they didn’t need to look at cyclic failure [failure caused by repeated use],” Oskay says. “As we get more confidence with the materials, it becomes evident that cyclic failure is possible.”

In the Pipeline

More composites are also appearing in automobiles, largely because they are lighter than metals and contribute to greater energy efficiency. Oskay has investigated whether composite carbon-reinforced fibers can replace metal in shock absorbers. “The way they [composites] fail is different than traditional met als. Metal will bend—a tube will buckle and absorb energy,” Oskay says. “If you have a brittle material, it crushes into little pieces. Each crushing event that happens is absorbing the energy.” Composite materials can actually absorb more energy than metal, but more needs to be understood about these new materials, he says.

Creating materials that can make vehicles lighter will be important for more than automobiles. Their use can be expanded into areas such as aircraft and tanks, Oskay says. Lighter vehicles can maneuver in different terrains, be carried by air or watercraft, and are less likely to get stuck in mud. Before the new materials can be used, however, engineers like Oskay need to understand how these composite materials perform and fail.

Another area of research also began with military implications but could prove important in other areas. Oskay and his lab are studying polyurea, a soft composite material that has shown to have tremendous blast resistance. While the military applications are obvious—in everything from ships and tanks to soldiers’ helmets—there are other uses as well. Oskay cites recent gas pipeline explosions in New York and California. If those pipelines had been coated with polyurea, the damage could have been limited and deaths from pipe shrapnel might have been avoided.

Oskay and Paul Sparks
Oskay encouraged Paul Sparks, BE’08, MS’11 (right), to focus on engineering research. A Ph.D. student, Sparks says he’s never looked back.

Oskay’s particular research explores uses of polyurea as a coating for composite or metallic materials, especially if it includes nano- or micro-inclusions to make it stiffer. “We’ve seen that the thicker the material, the better it is. If you confine it [polyurea], the better it is,” he explains. “We are actually coming up with some answers—we’re trying to see if we can come up with a material that has optimal blast resistance.”

“The material is there; it’s not something that is unobtainable,” Oskay says. “We are trying to understand [the material] so that we can tweak it in a way to make it work better. It is close to being applied to real structures.”

Crossroads of Materials, Structures and Math

Oskay’s focus on real-world applications is at the heart of all his research, including creating mathematical formulas to explore microstructures of complex materials. “We’re trying to bring the impact of multiscale modeling, which has had a tremendous impact on academia, to something that can be useful in industry. We’re trying to come up with methods that will transition tools that are being developed and bring them to industry.”

His career path—which he says is “not linear”—has taken him far from his original intention: to study soil and soil properties during earthquakes. Earthquakes are extremely common in his native Turkey, and he endured several there. A love of math and computers drew him into computational mechanics. After completing his doctorate in civil engineering at Rensselaer Polytechnic Institute in Troy, N.Y., he stayed for three years as a postdoctoral student further exploring multiscale computational mechanics.

“This field is at the crossroads of materials, structures and math,” he says. “It gives me the opportunity to understand systems and the science of things and come up with tools that are useful to everybody.”

Endless Possibilities

Oskay pushes the researchers in his laboratory to broaden their approaches as well. Paul A. Sparks, BE’08, MS’11, who is pursuing his doctorate in structural mechanics and materials, says Oskay encouraged him to think beyond a traditional design engineering career. “He posed the question, ‘Paul, wouldn’t you prefer to be at the forefront of research and innovation within your field?’” Sparks says. “And I thought to myself, ‘Indeed.’ Solving complex problems which don’t have solutions is much more rewarding than being a design engineer. I have never looked back since that day.”

Material Test
Tests Oskay ran on these composite material samples demonstrate differences in strength and durability. The materials may one day be used by the U.S. Navy.

Sparks has joined Oskay in working with the Air Force Research Laboratory in Ohio, where he gained new insight into his adviser. “It was there that Dr. Oskay exposed me to the inner workings of the endless possibilities of research and the importance of collaborating with professionals across the realm of academia,” Sparks says. “Not only is he committed to academic excellence, but he is concerned with my general well-being and growth.”

Oskay may make himself an expert in the topic of failure, but the line ends there. It’s not a subject in which he allows his students, his research or himself to excel.