From the Air Force Materiel Command News Service:
Engineers here are testing a new kind of transparent armor – stronger and lighter than traditional materials – that could stop armor-piercing weapons from penetrating vehicle windows. The Air Force Research Laboratory’s materials and manufacturing directorate is testing aluminum oxynitride – ALONtm – as a replacement for the traditional multi-layered glass transparencies now used in existing ground and air armored vehicles.
…ALONtm is a ceramic compound with a high compressive strength and durability… “The substance itself is light years ahead of glass,” said 1st Lt. Joseph La Monica, adding that it offers “higher performance and lighter weight.” ..ALONtm is virtually scratch resistant, offers substantial impact resistance, and provides better durability and protection against armor piercing threats, at roughly half the weight and half the thickness of traditional glass transparent armor, said the lieutenant.
…”With glass, to get the protection against higher threats, you have to keep building layers upon layers. But with ALONtm, the material only needs to be increased a few millimeters.” …”Eventually, with a conventional glass surface, degradation takes place and results in a loss of transparency,” Ron Hoffman, an investigator at University of Dayton Research Institute, said. “Things such as sand have little or no impact on ALONtm, and it probably has a life expectancy many times that of glass.”
…”Traditional transparent armor costs a little over $3 per square inch. The ALONtm Transparent Armor cost is $10 to $15 per square inch,” Lieutenant La Monica said. “The difficulties arise with heating and polishing processes, which lead to higher costs. But we are looking at more cost effective alternatives.”