Enhancement of antiballistic behavior of Kevlar fabric by nanofluid reinforcement

In this work the possibility to increase the resistance upon ballistic impact of typical Kevlar-based materials by means of silica nanofluids is investigated. Nanofluids are commonly known to have non-newtonian behavior, also indicated as shear thickening fluid (STF) property. STFs are very deformable materials in ordinary conditions (flowing like a liquid as long as no force is applied), but they turn into a very rigid solid-like material at high shear rates. The nanofluid optimization, mainly regarding its chemical and thermal stability, as well as the STF/fabric chemical coupling are crucial issues to tackle, in order to suitably exploit the STF property, i.e. to increase the fabric resistance upon impact. The present work summarizes some experimental results obtained on this subject. In particular, different kind of nanofluids realized by including several percentages of silica nanoparticles within polyethylene glycol are analyzed in terms of their morphology and rheological properties. Later on, the treatment with nanofluids of different typologies of Kevlar materials and the test panels manufacturing is described. Finally, the results of the ballistic characterization of the panels is presented and widely discussed. This latter is performed by means of an in-house built electromagnetic Coil Gun, able to explore a relatively large range of bullet velocity (up to 90m/s) with excellent precision and high degree of test reproducibility. The preliminary results obtained in such energy range show that STF impregnated fabrics have better penetration resistance compared to neat Kevlar, without affecting the fabric flexibility and, mainly, without overweighting the whole panel. That indicates that the addition of STFs to conventional ballistic fabrics enhances the material performances, thus suggesting further investigations in order to make such nanoreinforced materials effective for ballistic applications.