Using Depth-of-Penetration Tests to Design Transparent Armor

The depth-of-penetration (DOP) test has been modified for application to transparent armor materials. Armor materials to be tested are bonded to a polycarbonate substrate and penetration into the substrate measured. The tests can be used both for comparing armor materials and for evaluating laminate parameters. Materials tested were all armor-grade transparencies: borosilicate glass, soda-lime glass, glass ceramic, and spinel. For blunt projectiles, armor material performance is inversely correlated with density. For hard, sharp projectiles, material strength is most important, with spinel providing the best performance. The efficiency of spinel-glass laminates was only weakly dependent on the spinel thickness. Linear scaling can reconcile data obtained with different size projectiles. Relatively thick bond layers do not adversely affect the efficiency of laminates. DOP tests can be used to evaluate effects of damage from single cracks and multiple hits, and results also provide an estimate of optimal armor design against the threat used in the DOP experiments.