Abstract: Although the bullet-proof plates made by single armor steel or the armed fiber have good characteristics of anti-penetration to high-speed bullet,but the compound structure can greatly increase bullet-proof properties and reduce its area density． The propertities of penetration of the sandwich structure with foam and armor steel reinforced by the armed fiber under the 56 types with 7.62 mm common steel core bullet are studied by experiments and numerical analysis． The protective ability of anti-bullet and influence factors of the absorbing bullet kinetic energy have been researched through the different compound forms of foam sandwich structure． The concept of the best bullet-proof speed zone and V₅₀ homologous formula in the structure are given． So the bullet-proof plates with the best benefit-cost ratio can be designed．

Key words: compound material, sandwich structure, bullet-proof plate, penetration, ballistic tests, numerical simulation, the best bullet-proof speed