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t proof vest called multilayered armor system (MAS) is intended to protect personnel and systems against relatively heavy ammunition with initial bullet velocity faster than 700 m/s, associated with high impact energy and perforating power. A typical MAS consists of a ceramic tile front layer, which dissipates most of the impact energy by means of the projectile deformation, erosion, and fragmentation.[1–4] The initial compressive wave is reflected as tensile wave at the back of the tile and also causes fragmentation of the brittle ceramic.[1] The resulting fragments of both projectile and ceramic, SERGIO N. MONTEIRO, E´DIO P. LIMA Jr., LUIS HENRIQUE L. LOURO, Professors, and LUIS CARLOS DA SILVA, DSc Student, are with the Department of Mechanical and Materials Engineering, Military Institute of Engineering, Prac¸a General Tibu´rcio, 80, Rio de Janeiro, 22290-270, RJ, Brazil. Contact e-mail: [email protected] JAROSLAW W. DRELICH, Professor, is with the Department of Materials Science and Engineering, Michigan Technological University, Houghton, MI 49931. Contact e-mail: [email protected] Manuscript submitted September 10, 2014. Article published online December 3, 2014 METALLURGICAL AND MATERIALS TRANSACTIONS A

depending on the ammunition power, might still possess enough energy to damage systems or inflict lethal trauma to personnel. Therefore, another second layer is bonded to the ceramic tile to further reduce the fragment’s kinetic energy.[5] For this purpose, plies of aramid fabric such as Kevlar are today commonly used to back the front ceramic tile in the MAS.[6] A complete MAS also possesses a third metallic layer acting as a final barrier.[3] The high strength aramid fabric is a well-known material used in single body armor vest against relatively medium-power ammunition with initial bullet velocity lower than 600 m/s. In this case, the energy dissipation needed to attend the NIJ standard[7] is basically provided by mechanisms of fiber rupture, debonding, and stretching as well as yarn pullout in the aramid fabric.[6] In particular, Moryet et al.[8] found that the major energy absorption mechanisms by an aramid fabric are: the tensile failure of the primary yarns, the elastic straining of the secondary yarns, and the kinetic energy of the deformed cone on the back face of the material. In the present communication, it will be shown that an additional mechanism of energy dissipation provided by the layer of aramid fabric in the MAS is to stop the ceramic fragments produced during the projectile impact with the front ceramic tile. In fact, the aramid fabric alone is not found to be an efficient protection against a sharp-pointed projectile with an impact velocity above 800 m/s. A capturing process of the ceramic fragmentation by the aramid fibers is also analyzed and discussed based on the scanning electron microscopy analysis of the fabric after projectile impact. Ballistic tests were performed with MAS targets composed of a front 15-mm-thick 4 pctNb2O5-doped Al2O3 ceramic layer bonded to a 10 mm aramid fabric