Blast-resistant glass

University of Missouri researchers are developing and testing a new type of blast-resistant glass that will be thinner, lighter and less expensive than commercial products currently on the market.

Sanjeev Khanna, associate professor of mechanical and aerospace engineering in the Missouri University College of Engineering, said: ’Currently, blast-resistant window glass is more than 1in thick, which is much thicker than standard window glass that is only one-fourth of an inch thick and hurricane-protected window glass that is one-half of an inch thick.

’The glass we are developing is less than one-half of an inch thick. Because the glass panel will be thinner, it will use less material and be cheaper than what is currently being used.’

Conventional blast-resistant glass is made with laminated glass that has a plastic layer between two sheets of glass. The researchers are now replacing the plastic layer with a transparent composite material made of glass fibres that are embedded in plastic.

The glass fibres add strength because, unlike plastic, they are only about 25 microns thick and leave little room for defects in the glass that could lead to cracking. The use of a transparent composite interlayer provides the flexibility for the researchers to change the strength of the layer by changing the quantity and orientation of the glass fibre.

In tests, the researchers are observing how the glass reacts to small-scale explosions caused by a grenade or hand-delivered bomb. They tested the glass by exploding a small bomb within close proximity of the window panel. After the blast, the glass panel was cracked but had no holes in the composite layer.

Khanna added: ’The new multilayered transparent glass could have a wide range of potential uses if it can be made strong enough to resist small-scale explosions. The super-strong glass also may protect residential windows from hurricane winds and debris or earthquakes. Most hurricane damage occurs when windows are punctured, which allows for high-speed wind and water to enter the structure.’

The research is funded by a $250,000 (£149,800) grant from the US Science and Technology Directorate of the Department of Homeland Security. Future tests will be done on larger pieces of glass that are equivalent to standard window size, and researchers could potentially test the glass using large-scale explosions.