The purpose of this study is to investigate the effectiveness of composite armor against 7.62 mm ballistic threats. A sandwich panel construction consisting of a 96% alumina ceramic strike face, an annealed aluminum alloy 7075 cubic lattice sandwich panel, and a thin aluminum backing plate were used to create hard armor. The ballistic test based on NIJ standard level III was performed using 7.62 mm × 51 mm NATO projectiles at an impact velocity of 847 ± 9.1 m∙s-1. The influences of the alumina strike face panel with thicknesses of 7, 10, and 14 mm on the ballistic performance were investigated. The results of the ballistic test suggest that hard armor designs can resist a ballistic impact of 7.62 mm × 51 mm NATO projectiles without penetrating them. With the increase in thickness of alumina ceramic tile, the deformation of the aluminum backing plate decreased. Furthermore, the annealed aluminum alloy 7075 cubic lattice sandwich panel could be able to absorb the residual kinetic energy of the projectile after it was eroded by the ceramic strike panel. The damaged targets after ballistic impact were presented. Collectively, these results indicate that the armor composites in this study may be used in military vehicle applications.
The use of zirconia dental ceramics has grown in recent years due to improvements in esthetics and biocompatibility. Zirconia is used in dental applications for its high strength and fracture toughness. In this research, the influence of sintering conditions on the strength and optical properties of zirconia was investigated. Spray dried granules of 3Y-TZP zirconia were die pressed into disc-shaped samples and cold isostatic pressed at 250 MPa. Sintering was conducted using either one step sintering at 1500 oC or two-step sintering, with pre-sintering at 1200 oC and final sintering at 1500 oC. Heating rates of 2 and 10 oC/min were used. The biaxial flexural strength, fracture toughness, density, microstructural characteristics and optical properties of the sintered samples were determined. It was found that the sintering conditions did appear to influence the mechanical and optical properties. The sintering conditions had no significant effect on the density. It was concluded that for the sintering conditions examined, the two-step sintering with a heating rate of 2 oC/min produced the best average mechanical and optical properties of 3Y-TZP zirconia.
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