Transparent armour having improved ballistic properties

Abstract

This disclosure teaches the use of low density, “open”-structure glasses as backing glasses, behind glass-ceramic strike-faces, in transparent armor composite windows. These low density “open-structure’ glasses are sometimes referred to as “anomalous” glasses. For transparent armor applications both silica, including fused silica, and borosilicate glasses can be used as backing glass. These backing glasses provide improved ballistics performance over that of standard commercial soda lime backing glass. These glasses should be used either in their as-formed state (e.g. float surfaces) or should be finished using a process designed for minimizing sub-surface damage.

1 . A transparent glass-ceramic/glass armor system, said system comprising:
 a glass-ceramic layer having a strike face and a bonding face, said faces having been finished after the glass-ceramic is made from a glass material capable of being cerammed, and;   one or a plurality of anomalous backing glass layers, one of said glass layers being bonded to the bonding face of the glass-ceramic layer, and, when a plurality of glass backing layers are present, the remainder of the backing glass layers being bonded sequentially to the layer bonded to the backing glass layer bonded to the glass-ceramic and   a spall-catcher layer bonded to the glass layer furthest from the glass-ceramic layer;   wherein said transparent glass-ceramic/glass armor system has a V50 greater than 2950 ft/sec, and said backing glass layer has a surface with a roughness of less than 3 Angstroms Ra.   
     
     
         2 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein the backing glass is a glass sheet having a composition consisting essentially of 75-85 wt % SiO 2 , 10-15 wt % B 2 O 3 , 1-3 wt % Al 2 O 3 , and 3-5 wt % Na 2 O, and 0.3-2 wt % K 2 O. 
     
     
         3 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein the backing glass is an as-formed float glass composition consisting essentially of 75-85 wt % SiO 2 , 10-15 wt % B 2 O 3 , 1-3 wt % Al 2 O 3 , and 3-5 wt % Na 2 O, and 0.3-2 wt % K 2 O. 
     
     
         4 . The transparent glass-ceramic/glass armor system according to  claim 2 , wherein the backing glass has a surface roughness in the range of 0.5-2 Angstroms Ra. 
     
     
         5 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein the backing glass consists essentially of 100 wt % SiO 2  glass 
     
     
         6 . The transparent glass-ceramic/glass armor system according to  claim 5 , wherein the backing glass has a surface roughness in the range of 0.5-2 Angstroms Ra. 
     
     
         7 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein the backing glass consists essentially of 100 wt % chemical vapor deposited SiO 2  glass having low sub-surface damage, said glass having a surface roughness of less than 2 Angstroms Ra. 
     
     
         8 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein said armor system has V50/AD Figure of Merit of at least 150. 
     
     
         9 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein said armor system has V50/AD Figure of Merit of at least 160. 
     
     
         10 . The transparent glass-ceramic/glass armor system according to  claim 1 , wherein said armor system has V50/AD Figure of Merit of at least 180. 
     
     
         11 . A transparent glass-ceramic/glass armor system, said system comprising:
 a glass-ceramic (“GC”) layer having a strike face and a bonding face, an anomalous glass backing layer bonded to the GC layer and a spall-catcher layer bonded to the glass layer furthest from the glass-ceramic layer;   wherein the backing glass consists essentially of 75-85 wt % SiO 2 , 10-15 wt % B 2 O 3 , 1-3 wt % Al 2 O 3 , and 3-5 wt % Na 2 O, and 0.3-2 wt % K 2 O, and   said transparent glass-ceramic/glass armor system has a V50 greater than 2950 ft/sec, and   said backing glass layer has a surface with a roughness of less than 3 Angstroms Ra.   
     
     
         12 . The transparent glass-ceramic/glass armor system according to  claim 11 , wherein the armor system has a V50/AD Figure of Merit of at least 150. 
     
     
         13 . The transparent glass-ceramic/glass armor system according to  claim 11 , wherein the armor system has a V50/AD Figure of Merit of at least 160. 
     
     
         14 . A transparent glass-ceramic/glass armor system, said system comprising:
 a glass-ceramic (“GC”) layer having a strike face and a bonding face, an anomalous glass backing layer bonded to the GC layer and a spall-catcher layer bonded to the glass layer furthest from the glass-ceramic layer;   wherein the backing glass consists essentially of a 100 wt % fused silica glass, and   wherein said transparent glass-ceramic/glass armor system has a V50 greater than 2950 ft/sec, and said backing glass layer has a surface with a roughness of roughness of less than 3 Angstroms Ra.   
     
     
         15 . The transparent glass-ceramic/glass armor system according to  claim 14 , wherein the armor system has a V50/AD Figure of Merit of at least 160. 
     
     
         16 . The transparent glass-ceramic/glass armor system according to  claim 14 , wherein the armor system has a V50/AD Figure of Merit of at least 180.