2015): The influences of particle-particle interaction and viscosity of carrier fluid on characteristics of silica and calcium carbonate suspensions-coated Twaron® composite, Journal of Experimental Nanoscience,
ABSTRACTThe effects of particleÀparticle interaction and viscosity of carrier fluid on steady and dynamic rheological responses and quasi-static penetration resistance of Twaron® fabrics treated with shear thickening and shear thinning suspensions have been investigated. The suspensions have been made by mechanically dispersing 60 nm silica (SiO 2 ) and calcium carbonate (CaCO 3 ) nanoparticles in poly ethylene glycol (PEG) with molecular weights of 200 and 400 g/mol. The CaCO 3 suspensions display shear thinning behaviour along with the total dominance of the elastic state over the viscous state while the SiO 2 suspensions exhibit shear thickening behaviour with the emergence of both the elastic and viscous states. With the increase of molecular weight of PEG, viscosity, viscoelastic modules and instability of the suspensions increase and critical shear rate and frequency of transition to elastic state diminish. The PEG200 and PEG400-contained SiO 2 suspensions-treated Twaron® composites at 35 wt.% have quasi-static penetration resistances which are nearly 2.63 and 2.48 times and maximum absorbed energies which are about 1.54 and 1.55 times higher, respectively, than those of the corresponding CaCO 3 ones. However, the influence of increasing the PEG's molecular weight is not as considerable as the effect of particleÀparticle interaction on the enhancement of penetration resistance performance.
Intelligent energy shunting fluid/fabric base structure which utilizes well-processed shear thickening fluid has been developed. The shear thickening fluid has been synthesized by a powerful mechanical stirrer to disperse 12 nm silica particles into polyethylene glycol 200 g/mol at three concentration levels from low to near maximum packing as 15, 25 and 35 wt%. Examining the rheological behavior of the shear thickening fluid indicates that the increase of shear thickening fluid concentration leads to significant increase in the suspension's initial, critical and ultimate (up to 10 4 Pa.s) viscosities, reduction of the critical shear rate, increase of viscoelastic modulus and instability of the suspension. The quasi-static puncture test results demonstrate with the increase of shear thickening fluid concentration, the maximum bearable load by the 15, 25 and 35 wt% shear thickening fluids-treated Twaron Õ composites increases by 132, 315 and 362%, and the energy absorption increases by 143, 159 and 209%, respectively, compared to the neat fabric. Regarding penetrator structure and dimension, by using rounded penetrators, windowing and pull-out mechanisms would be expected at low velocities. However, sharpnosed penetrators most likely cause yarns to push aside that is not taken into account Downloaded from as a perfect criteria for investigation of puncture resistance performance. Also, larger penetrators have a larger presented area of impact and, as a result, break more number of yarns to penetrate the fabric.
Perforation process of a novel ceramic/composite panel including alumina-silicon carbide (Al2O3-SiC) nanocomposite as the front plate and ultra-high molecular weight polyethylene laminated composite (Dyneema® HB25) as the back-up impacted by a tip tapered penetrator has been analyzed based on LS-Dyna and HyperMesh codes. In order to balance the competing requirements posed by thickness, weight, cost and performance, a finite element (FE) simulation has been developed with well-developed material models. A two-dimensional, dynamic-explicit and Lagrangian model has been considered. The perforation process has been investigated for three different thicknesses of the ceramic plate. The Johnson-Cook, Johnson-Holmquist and Orthotropic-Elastic material models have been used for the penetrator, ceramic, and composite, respectively. The FE results, which have a good agreement with available experimental data, show that with the increase in the ceramic thickness, ceramic's fracture conoid as well as elasto-plastic deformation of fibers increase while fiber breakage and dishing of the composite layers diminish. In addition to saving cost and time, the FE simulation results can be useful as a fairly accurate prediction tool for the designing of lightweight body protective panels with desired impact resistance performance and eligible blunt trauma of the back-up.
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