Ballistic characterization of meta-configured structures

Drawing inspiration from metamaterials, meta-configured structures (MCS) are investigated to ascertain their ballistic characteristics. In MCS, a confluence of hybrid materials and designs is used to enhance ballistic performance making them amenable to multifunctional integration with acoustic applications. Firstly, ballistic performance of hybrid materials such as silica nanoparticle-impregnated Kevlar (SNK) fabrics was evaluated using gas-gun tests. A loss-compensated model was developed to predict the projectile velocity for gas-guns with greater accuracy. A colloid-based treatment process was developed to impregnate dry nanoparticles into the fabric. Using digital image analytics, a fast, full-field, and cost-effective alternative to conventional inspection techniques for treated fabrics was developed. The flexibility of SNK was evaluated by a new fixed cantilever test. Ballistic tests show that 40 wt.% SNK has ~17 % mass advantage (owing to three less layers) vis-à-vis neat Kevlar for the non-penetrative case due to enhanced friction. SEM imaging reveals nanoparticles agglomerate in yarn interstices, better engaging secondary yarns away from the impact location. A semi-empirical model was developed to predict the kinetic energy absorbed for SNK. Influence of nanoparticle’s material and geometry on ballistic performance of treated fabrics was studied. Silica, alumina, and zinc oxide nanoparticles ranging from 10-125 nm, with spherical or cylindrical shape were considered. The 80-nm silica-treated samples performed significantly better than others due to increased agglomeration and mechanical interlocking. The exit-face damaged zone area acts as a surrogate for energy absorbed correlating well across all samples. Treating the layers in a sample together instead of individually gives nearly 21 % higher energy absorption due to volumetric frictional interactions. Quasistatic yarn pullout tests reveal that the peak pullout force increases with nanoparticle addition until a threshold is reached. Fitting coefficients for various pull-out regimes were calibrated to model yarn pull-out behavior for treated fabrics. Finally, a prototypical MCS combining SNK with other structural materials through a bio-inspired design is fabricated and tested. Fabric pleating was optimized using an analytical model. MCS displayed a 37 % increase in energy absorption over conventional counterparts. MCS is a promising multifunctional structural solution in applications for personal protection, ballistic containment, and military structures.