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Mizzou Engineering building security with new blast-resistant glass

Photo composite shows a pane of blast resistant glass developed by Sanjeev Khanna, a mechanical and aerospace engineering associate professor, Zhen Chen, a civil and environmental engineering professor in it's original form at top, during the blast conducted at an approved site in Rolla, and shows Khanna inspecting it after the blast.

Airports and government buildings soon may be less vulnerable to small-scale explosions thanks to a blast-resistant glass that two Mizzou Engineering researchers are developing.

Sanjeev Khanna, a mechanical and aerospace engineering associate professor, and Zhen Chen, a civil and environmental engineering professor, have received a $250,000 grant from the U.S. Department of Homeland Security’s Science and Technology Directorate to develop and test a new type of explosion-resistant glass. Much thinner and less expensive than traditional blast-resistant glass, the new multilayered transparent glass would have a wide range of potential uses if it can be made strong enough to resist small-scale explosions, Khanna said.

“What we are going to study is how this material will react to the type of explosions you’d get from a grenade or a hand-delivered bomb,” Khanna said.

Government funding began in June 2008 to test the laminated glass, which draws its strength from a layer of glass fibers embedded in plastic. The glass fibers add strength because they are only about 25 microns thick-about half the thickness of a typical human hair-with little room for defects that could lead to cracking, Khanna said. Joined on either side to glass sheets, this layer creates a tough and transparent glass window panel.

Engineering researchers tested the glass May 6 by exploding a small bomb within five feet of the window panel. The glass panel withstood the blast with no holes in the composite layer.

With that success in hand, Khanna and Chen also plan to study whether using nanoparticles-the name given to microscopic materials so small that their natures change-could strengthen the adhesion between different layers. That bonding between layers plays a large role in whether or not glass breaks upon impact, Chen said.

“So if we can optimize the adhesion between layers in the composite window system, we may be able to improve the impact and blast resistance,” Chen said.

Ultimately, Khanna and Chen are trying to devise a glass of similar strength but thinner and lighter than conventional blast-resistant glass, which may be more than an inch thick. Mizzou Engineering’s blast-resistant glass is less than a half inch thick and would cost a fraction of what such glass currently costs, paving the way for a number of protective uses, Khanna said.

“Once we know under what scenarios we can use it, then we can appropriately apply it,” Khanna said.

Among those scenarios are several civilian ones, he said. The super-strong glass could protect residential windows from hurricane winds and debris or earthquakes, Khanna said.

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