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The ballistic perforation response of knits formed from continuous filament aramid is reported and compared to conventional armor textiles and commodity fabrics. The ballistic experiments consist of 6.0-mm-diameter glass spheres impacted into gelatin-backed targets with areal densities from 200 to 1000 g/m 2 . These ballistic experiments are complemented with quasistatic reverse-perforation experiments to gain insights into deformation and failure for these materials. In-plane stretch experiments are also performed to quantify modulus and strain-to-failure. The results show that, while the ballistic performance of traditional woven textiles is generally superior to knitted aramids, knits formed from continuous filament aramid are significantly better than knits formed from staple yarn. Knitted structures are limited by two main factors: failure of a single yarn tends to lead to catastrophic deconstruction and perforation, and the low in-plane modulus of knits leads to poor lateral stress transfer and energy distribution during higher speed impact. Importantly, however, knits provide significantly more reversible elongation with less elastic resistance compared to other structures, such as woven textiles, making them well-suited for wearable protection in which comfort is critical. The results also show that continuous filament knits can be produced with commercial manufacturing equipment, and that barriers composed of few layers of high-denier yarn knits likely provide more efficient ballistic resistance than equivalent weight barriers composed of many layers of low-denier yarn knits. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical response of a thermoplastic elastomer synthetic ballistic gel is studied over a range of strain-rates. Experiments were conducted at room temperature under uniaxial stress compression at rates ranging from 0.001 to 500/s. Low-rate experiments (<1/s) were conducted with a servo-hydraulic load frame. High-rate experiments (>100/s) were conducted with a polymeric Kolsky bar, along with several modifications to improve data quality. These modifications include the use of a commercial force transducer, a normal displacement interferometer, and a line laser extensometer. Because of the low shear strength and comparatively high compressibility of these materials, inertial effects are very pronounced. Specimen size is varied in an effort to study inertial effects at various loading rates. High speed photography is also used to demonstrate the presence of non-uniform deformation, due to both inertia and friction between the specimen and the loading surfaces. Finally, numerical simulation is used to verify trends observed in the experiments and further validate the data. It is concluded that this material is rate sensitive, with an almost three-fold increase in stiffness over the range of strain-rates studied. [Copyright &y& Elsevier]