Randomly crumpled and purposefully folded polymeric materials could hold the key to producing lightweight and strong components for more efficient aircraft and spacecraft.
Andrew Croll, assistant professor of physics, is receiving a $305,046 three-year award from the U.S Air Force Office of Scientific Research to study the possible real-world applications of “thin films,” or extremely thin slivers of layers of material—tens of nanometers thin. The competitive award is being made through the prestigious Young Investigator Research Program. The grant also will provide funds for undergraduate and graduate students to work as part of the research team. A North Dakota Governor’s School student also may be selected to participate in the research.
Croll’s proposal is titled “Crumpled and Prescriptively Folded Polymer Films for Advanced Lightweight Materials.” If more efficient aircraft and spacecraft are to be manufactured, new materials that are both rigid and lightweight must be developed. The structure and properties of the materials must be defined. The stuff they are made of is studied. Scientists probe and measure how the materials respond to various forces to determine how they might respond in real-world applications. The research by Croll and his team is being conducted to establish a basic understanding of the focused bending and stretching that leads to high strength-to-weight ratios in folded polymer films.
Carbon fiber composites and nanocomposites are currently one of the leading lightweight, yet rigid, materials available for aircraft design. Goals of the research by Croll include determining the basic physics behind the growth of more complex crumpled objects that can easily hold considerably higher loads.
“The research has the potential to shift development from costly new materials to the creative use of existing materials,” said Croll. “We are trying to build an understanding of how and why thin polymer films feel strong when bent in particular ways. For example, a piece of paper is flimsy, but if crumpled into a ball, it can be surprisingly strong. Paper also can be folded into intricate, functional shapes, as any origami artist knows. If the strength of the bends making up origami and crumpled balls of paper, for example, were completely understood, then engineers can use bends as ‘structural building blocks.’”
Much of the physical world is complex—not fancy exotic materials at large (space) or small (quantum) length scales–but materials at moderate sizes that have structure on many different scales. Complex systems often show behavior that is hard to predict. A crumpled ball is an example of something complex. Its strength has to do with its complex bent-up shape, not just the material of which it is made.
“If we can find ways to predict how strong a crumpled ball is, we have the potential not only to use crumpling in engineered systems, but may also gain insight into many other complex systems,” said Croll.
The research holds potential for military and other applications. Crumpled films form a very strong, lightweight building material with the potential for 'active' material responsiveness. Lightweight materials drive down fuel costs.
Materials that are responsive could create new technologies. The advanced materials that could be created might be the stuff of science fiction movies brought to life. Applications could include solar cells that deploy themselves in space, materials that are rigid in one direction and soft in another, or materials that can fold up and “hide” or walk.
“For these advanced materials to be a reality, the basic building blocks must be completely understood,” said Croll.
He also is examining the connections between bending and failure of thin polymer systems. Potential applications for this research might include flexible electronic systems. Such systems could be embedded in wearable performance-monitoring equipment. Antennas could conform into the curving skin of an airplane, ship or other vehicle. Folded, deployable solar panels could be another eventual outcome of this research.
The award funding to Croll announced by the U.S. Air Force Office of Scientific Research is one of 57 grants at 43 research institutions and small businesses. Croll’s work was selected out of 200 proposals. The Young Investigator Research Program is open to researchers in the early stages of their careers who show exceptional ability and promise for conducting basic research.
Other awardees include representatives from Princeton, California Institute of Technology, Stanford University, Arizona State University, Cornell University and Rensselaer Polytechnic Institute.
Croll joined the faculty at NDSU in 2010. He completed a post-doctoral fellowship at the University of Massachusetts. He received a doctorate in polymer physics from McMaster University, Hamilton, Ontario, Canada. Croll received a bachelor’s degree in physics from the University of Waterloo, Ontario, Canada.
While physics might not be the topic of everyday conversation, Croll makes an effort to bridge that gap. He previously spoke at a Science Café, discussing “Why Stuff Sticks: Geckos, Bugs, Nanotechnology and the Quest for Really Good Duct Tape.”
Sharing research information with the public is important, Croll said. He also finds it fun. “I do it to excite people, to try to share the joy I find in seeing something new. I do it for fun, so I can act ‘not’ my age.”
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