Natural Curaua Fiber-Reinforced Composites in Multilayered Ballistic Armor
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ARMORED vests for human protection against relatively heavy ammunition, such as the 7.62 9 51 mm caliber bullet, require a light shielding system with high impact absorption and resistance to penetration. A monolithic layer, typically a steel plate,[1] cannot provide the necessary protection unless it is comparatively thicker, which compromises lightness and portability. Multilayered armor systems (MAS) combining relatively lighter materials are currently extensively investigated[2–4] and used as portable vests. The MAS aims not only to absorb the impact energy of a higher velocity projectile but also to impede the penetration of fragments.[5] Indeed, a portable armor vest for body protection should be a low-cost and lightweight wearable garment system with ballistic impact resistance.[6] The NIJ standards[7] specify that body armor should stop a projectile and SERGIO NEVES MONTEIRO, LUIS HENRIQUE LEME LOURO, WILLIAN TRINDADE, CARLOS NELSON ELIAS, CARLOS LUIZ FERREIRA, EDUARDO DE SOUSA LIMA, RICARDO PONDE´ WEBER, JOA˜O CARLOS MIGUEZ SUAREZ, ANDRE´ BEN-HUR DA SILVA FIGUEIREDO, WAGNER ANACLETO PINHEIRO, and E´DIO PEREIRA LIMA, Jr., Professors, and LUIS CARLOS DA SILVA, Ph.D. Student, are with the Department of Mechanical and Materials Engineering, Military Institute of Engineering-IME, Prac¸a General Tibu´rcio, 80, Rio de Janeiro, RJ 22290-270, Brazil. Contact e-mail: snevesmonteiro@gmail. com Manuscript submitted April 24, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS A
prevent its penetration into a clay witness backing the armor to a depth not exceeding 1.73 in. (44 mm). Beyond this depth, the penetration can potentially cause serious blunt trauma to the armor wearer.[8] MAS are usually composed of a harder front ceramic tile with the ability to deform and erode/fracture the projectile.[9–11] Owing to this ceramic frontal layer, a great deal of the projectile energy is dissipated through dynamic fragmentation involving nucleation, growth, and coalescence of microcracks.[12] It is known that once a highenergy projectile strikes the front ceramic tile, a compressive wave propagates and reaches the back of the tile.[13] There, the wave could be partially reflected as a tensile pulse, which normally breaks the ceramic tile regardless of the interlayer material connecting the following layer.[4] A second MAS layer backing the ceramic tile might be chosen as a lighter composite material, which reduces even more the impact wave by absorbing part of the fragments (projectile or ceramic) kinetic energy. For this second layer, glass fiber composites originally were preferred[14,15] and carbon fiber composites were investigated.[16,17] Today, however, aramid fabric such as Kevlar (DuPont, Richmond, VA) and Twaron (Teijin Aramid, Conyers, GA)[6,18] as well ultrahigh-molecular polyethylene fiber such as Spectra (Spectra Energy Corporation, Houston, TX) and Dyneema (DSM Dyneema LLC, Stanley, NC)[19,20] reinforcement are becoming the choices for lightweight body armor composites. In particular, aramid fiber (Kevlar 49) is o
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