High cost, processing hindrances, and restrictions to predict ballistic performance from the properties of the material are some drawbacks of ceramic armors. The main ceramic materials used commercially in the development of ballistic armors are Al 2O 3, B 4C, SiC, and ceramic matrix composites (CMCs) such as Al 2O 3/ZrO 2 system. Fracture toughness is also a very important requirement for this application. Thus, it is necessary that the ceramic material presents high elastic modulus and high hardness. Ceramic materials for using as ballistic armor must be sufficiently rigid to fragment the bullet and reduce its speed, transforming it into small fragments that should be stopped by the layer of flexible material that supports the ceramic. IntroductionĬeramics have been considered one of the most important materials for lightweight armor applications due to their low density, high compressive strength, and high hardness. None of the five shots penetrated or even deformed the metal sheet, showing that the composition containing 92 wt% Al 2O 3 could be considered to be a potential ballistic ceramic, being able to withstand impacts with more than 4000 J of kinetic energy. Five alumina plates were used in the ballistic tests (one shot per plate). Standard NIJ-0108.01 was followed in regard to the type of projectile to be used (7.62 × 51 AP, Level IV, 4068 J).

Plates (120 mm × 120 mm × 12 mm) of this composition were selected for ballistic testing according to AISI 1045, using a metallic plate as backing and witness plates in the case of penetration or deformation. Results showed that the strength values ranged from 210 to 300 MPa depending on the porosity, with lower standard deviation for the 92 wt% Al 2O 3 sample. Relative density, Vickers hardness, and four-point flexural strength measurements of samples after sintering were performed. Samples were pressed at 110 MPa and sintered at 1600☌ for 6 h. Three compositions (92, 96, and 99 wt% Al 2O 3) were tested for 10 mm thick plates processed in an industrial plant.

The aim of this work is to present results of mechanical characterization and ballistic test of alumina-based armor plates.

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