Unique glass offers new pane of terror Thin, inexpensive blast-resistant window material emerges in lab
By Doug Page
Flying shards of glass are a leading cause of death and injury following terrorist bombings. For example, more than 90 percent of the people injured during the 1996 Khobar Towers bombing in Saudi Arabia suffered laceration injuries, many of them significant.
In any structure, windows are typically the most vulnerable part of the building. Flying and falling jagged pieces of broken glass are also major hazards during hurricanes and earthquakes strong enough to shake the windows loose.
University researchers may have an answer. A team of scientists at the University of Missouri, along with colleagues at the University of Sydney in Australia, are developing a blast-resistant glass that is not only lighter and thinner than existing glass, but is strong enough to withstand the force of an explosion, earthquake or hurricanes winds.
"Developing a new and relatively low-cost window system could be very beneficial not only for general civil structures, but more so for the critical infrastructure from a homeland security standpoint," said University of Missouri mechanical engineer Sanjeev Khanna.
Unlike conventional blast-resistant windows made of pure polymer layers, the new design is a plastic composite no more than a quarter-inch thick. Current blast-resistant glass technology, such as the kind that protects the windows of key federal buildings, the president's limo and the Popemobile, is as thick as a 300-page novel, so thick it can't be installed in standard window frames, making it both difficult and expensive to blast-proof glass windows in present structures.
The new blast-resistant window material uses a unique transparent glass fiber reinforced polymer interlayer that can potentially replace customary PVB (polyvinyl butyral) or polycarbonate interlayers. The new transparent composite interlayer is sandwiched between glass sheets to fabricate the final window panel.
"The composite interlayer and the engineered interface between the interlayer and the glass sheets provides good resistance to fracture under blast loading," Khanna said.
Khanna said proof of concept has been demonstrated with a prototype of 18- by 27-inch window panels matched against small-scale explosions in the vicinity of the window.
"The results were fantastic," Khanna said. "While the discharge left the pane cracked, the front surface remained completely intact."
The design is currently being further engineered to double the size of the window panels and then test these larger windows under specific blast loading.
"After proving the new window performance, methods will be developed to automate the fabrication process if commercial production is desired," Khanna said.