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Impact experiments conducted on custom manufactured fabrics provide a systematic study of the effects of weave type on ballistic performance for aramid, ultrahigh molecular weight polyethylene, and hybrid aramid--ultrahigh molecular weight polyethylene fabrics. For the combination of projectile, yarn count, and yarn denier considered, the ultrahigh molecular weight polyethylene and hybrid fabrics show a strong and similar dependence of ballistic performance on weave type. The measured performance of the aramid fabrics was unexpectedly insensitive to weave type, although variations in target ballistic performance were the highest in the aramid fabric experiments. The experimental approach developed in this research is well suited for use in measuring the influence of additional parameters, such as projectile type, on the relative ballistic performance of various two-dimensional weaves. [ABSTRACT FROM AUTHOR]

In this study a new interference model is developed to investigate the ballistic response of a hybrid, two-layered, flexible body armor. Because the stacking order of layers, which have distinctly different mechanical properties, has a large effect on the V50 limit velocity for penetration, we apply the analysis to a two-layer system consisting of fabrics of aramid (Kevlar29®) fiber and of ultrahigh molecular weight and drawn polyethylene (Dyneema®) fibers. Using right-circular cylindrical projectiles, previous experimental results of Cunniff ("An Analysis of the System Effects in Woven Fabrics Under Ballistic Impact," Textile Research Journal, Vol. 62,1992, pp. 495-509) [using a similar fiber, Spectra® instead of Dyneema®] showed nearly a factor of 2 difference in the V50 velocity in the two possible stacking orders, that is, Spectra® versus Kevlar29® as the strike face. This new model extends our previous fundamental work ("A New Membrane Model for the Ballistic Impact Response and V50 Performance of Multiply Fibrous System," International Journal of Solids and Structures, Vol. 40, 2003, pp. 6723-6765) by addressing interference factors in terms of instantaneous material inflow to the impact cone using a convolution over current local strain around the projectile edge during its deceleration. Our previous multilayer model ("Modeling of System Effects in Ballistic Impact into Multi-Layered Fibrous Structures for Soft Body Armors," International Journal of Fracture, Vol. 135,2005, pp. 219-251) ignored the interference aspect though a subsequent work ("Effects of Layer Stacking Order on the V50 Velocity of Two-Layered Hybrid Armor System," Journal of Mechanics of Materials and Structures, Vol. 3,2008, pp. 627-639) approximated its effects but without instantaneous response of material inflow to local tensile strain. The current model is much more complete and produces velocity, strain, and deformation histories either to perforation or to halting the projectile. In the new model, V50 velocity differences with stacking order and with layer bonding versus no bonding are even larger. However, backface deflections turn out to be minimally affected. Calculations are very fast and postprocessing figures can be obtained in less than a minute using MATLAB with a laptop (2 MHz Core 2 Duo CPU 2 Gb RAM). [ABSTRACT FROM AUTHOR]

Structures undergo different loading conditions during their service life. Impact is one of the typical cases of loading. In this study, an analytical method is presented for the prediction of ballistic impact behavior of thick composites based on wave theory and energy balance between the projectile and the target. For thick composites the wave propagation along the thickness direction is also considered. During the ballistic impact event, energy transfer takes place from the projectile to the target. As the energy is absorbed by different mechanisms, kinetic energy and velocity of the projectile decrease. Different damage and energy-absorbing mechanisms for a typical woven fabric composite are compression of the target directly below the projectile, possible reverse bulge formation on the front face, compression in the surrounding region of the impacted zone, tension in the yarns, shear plugging, bulge formation on the back face, delamination and matrix cracking, friction between the target and the projectile, and beat generation caused by impact. Based on the analytical method presented, typical results are generated and compared with the experimental values. [ABSTRACT FROM AUTHOR]

Presents a study which analyzed internal ballistics and criteria for reaction propagation in nonelectrical tube explosive lines. Assumptions on the proposed analysis; Formulation of analysis; Conclusions.

The article discusses research that examined the effectiveness of a staged aft body at addressing its tail boom by using an aeroballistic range. It describes the evaluation of the loudness of a sonic boom according to overpressure and the perceived loudness. The details of the experiment carried out at Nagoya University in Japan are presented. The researchers noted the generation of an expansion fan and oblique shock by the staged aft body.