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Modeling clay is a soft malleable material made from oils and waxes. This material is fundamental for ballistic evaluation of body armors because it is used as backing material in ballistic tests. After a ballistic impact, a back-face indentation is measured to assess performance of the armor. Due to the important role of modeling clay in this particular application, its mechanical characterization and comprehension of penetration mechanics are essential for development of new personal protection systems. This paper presents a two-step computational methodology to calibrate parameters of a Cowper–Symonds material model for modeling clay at characteristic strain rates up to 1.8 × 10 4   s − 1 . In the first stage, a high-speed camera is used to record the penetration of a gas-gun launched cylindrical mass with a hemispherical cap into a block of clay. Image-processing software is used to capture the tail of the projectile as it penetrates into the clay. These data are then used to sample the penetration depth as function of time. In the second stage, an in-house developed model of penetration, based on both the spherical cavity expansion theory and the Tate penetration equation, is used to determine, by inverse analysis, the parameters of the Cowper–Symonds clay model. The proposed constitutive relationship for clay and the determined material parameters can be applied accurately to problems involving high strain rates. [ABSTRACT FROM AUTHOR]

A nacre-like composite armor consisting of BC tablets and polyurea matrix is modeled, and its ballistic impact behavior and penetration resistance (under a normal and a 15°-oblique impact by a solid right circular cylindrical projectile) were analyzed using a series of transient, nonlinear dynamic, finite-element analyses. Nacre is a biological material constituting the innermost layer of the shells of gastropods and bivalves. It consists of polygonal tablets of aragonite, tessellated to form individual layers and having the adjacent layers as well as the tablets within a layer bonded by a biopolymer. Due to its highly complex hierarchical microstructure, nacre possesses an outstanding combination of mechanical properties, the properties which are far superior to the ones that are predicted using the homogenization techniques such as the rule of mixtures. The results of the transient nonlinear dynamic analysis pertaining to the ballistic impact response and the penetration resistance of the modeled nacre-like armor are compared with their counterparts for the BC single-block armor having an identical areal density. Furthermore, the effect of various nacre microstructural features (e.g., surface profiling, micron-scale asperities, mineral bridges between the overlapping tablets lying in adjacent layers) on the ballistic penetration resistance of the nacre-like composite armor is investigated in order to identify an optimal nacre-like composite-armor architecture having the largest penetration resistance. The results obtained clearly show that a nacre-like armor possesses a superior penetration resistance relative to its monolithic counterpart, and that the nacre microstructural features considered play a critical role in the armor penetration resistance. [ABSTRACT FROM AUTHOR]

Ballistic performance of an armour steel at different tempering conditions against a tungsten heavy alloy long rod kinetic energy projectile has been investigated. The ballistic performance was found to increase with decreasing tempering temperature but the performance increments were not proportional to the strength increase caused by the tempering. Both target and projectile underwent fragmentation at the penetration interface in all the three targets. Apart from the strength target material deformation behaviour also showed considerable influence on ballistic performance. The ballistic performance appears to increase with decreasing toughness for a given strength. [ABSTRACT FROM AUTHOR]

The database for depth of penetration by projectiles into semi-infinite targets is quite extensive. The objective is to use the experimental semi-infinite penetration data to predict finite-thickness target effects. Similitude considerations are used to represent penetration response as a function of a normalized impact velocity, which is the ratio of the penetration pressure to the target strength. Then, a least-squares regression analysis methodology was applied to the normalized experimental data to provide an analytic expression for the normalized depth of penetration as a function of the normalized impact velocity over a very large velocity range, typically a few hundred meters per second to over 3500 m/s. We use the analytic expression, along with some simplifying assumptions, to estimate ballistic limit thickness T 50 and/or the ballistic limit velocity V 50 . If a target is overmatched, i.e., perforated by the projectile, an estimate is also made for the projectile residual velocity and residual length. The experimental data on which the regression fit is based consists of L / D 10 projectiles, so a procedure is also developed to account for different projectile aspect ratios. A series of examples are provided to demonstrate the utility and accuracy of the approach. [ABSTRACT FROM AUTHOR]