http://weekendpundit.blogmosis.com/images/clearalum%20640x460.jpg
Transparent aluminum was created in the late ninites or at least made public then. It was only able to be made in samll quantities.
The U.S. Air Force seems to have solved that problem as well as being able to manufacture somewhat larger sheets of the tough stuff.
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. When polished, it is the premier transparent armor for use in armored vehicles, said. 1st Lt. Joseph La Monica, transparent armor sub-direction lead
Traditional transparent armor is thick layers of bonded glass. The new armor combines the transparent ALONtm piece as a strike plate, a middle section of glass and a polymer backing. Each layer is visibly thinner than the traditional layers.
In a June 2004demonstration, an ALONtm test pieces held up to both a .30 caliber Russian M-44 sniper rifle and a .50 caliber Browning Sniper Rifle with armor piercing bullets. While the bullets pierced the glass samples, the armor withstood the impact with no penetration.
