Stiff, strong and stable composites

Posted on 27. Sep, 2013 by in Academic Departments, Annual Report, Engineering Physics, Issues, Research

It was a sweltering day on Long Island, and young Rod Lakes and his family were stuck in the middle of a traffic jam. Up the road, there was a drawbridge. Its two halves had expanded due to the heat and, instead of closing properly, the pieces overlapped.

Though at the time Lakes didn’t realize it, the experience neatly illustrated the concept of thermal expansion: Heat a material, and it will expand; cool the material, and it will contract. “That’s part of why things fail,” says the professor of engineering physics. “They expand and contract and fail to fit, or crack from thermal stress.”

While a laptop computer failure due to that warming and cooling might be personally catastrophic, the effects of thermal expansion are magnified in such aerospace applications as satellites or space telescopes, which don’t enjoy the benefits of an atmosphere that can help regulate their temperature.

Nearly two decades ago, Lakes encountered research that suggested there were high and low bounds on thermal expansion in a composite material, and he set out to create a lattice that pushed the high and low boundaries of thermal expansion in composite materials. His analysis yielded an open, honeycomb-shaped structure in which bilayer materials form the ribs. “If I make the rib elements of two different materials, I can get any expansion I want,” says Lakes. That was 1996.

Since then, other researchers have followed up, and recently, the U.S. Defense Advanced Research Projects Agency announced plans to build on the idea, particularly for applications in space.

Now, using common materials such as steel, aluminum and invar, Lakes and master’s student Jeremy Lehman have developed lattices that are tuned to exactly zero expansion, yet are optimized to be as stiff and strong as possible. Bucky Badger head

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