The quasi-static (QS) puncture resistance of p-aramid Twaron fabric impregnated with shear thickening fluid (STF) based on the molecular weight variation of the base liquid has been investigated. To synthesis the STF, the 12 nm silica particles have been dispersed in polyethylene glycol (PEG) with two different molecular weights, 200 and 400 g/mol by means of mechanical mixing. The weight percentages of silica particles in the continuous phase were selected as 15, 25 and 35 wt%. The results of rheological tests indicate that with the increase of the polymer's molecular weight, the viscosity and instability of the suspension increase, while its critical shear rate diminishes. The STF impregnated Twaron fabrics were subjected to QS puncture resistance tests according to the ASTM standard D6264. The quasi-static puncture resistance increased about 4.5 fold for Twaron fabric impregnated with 35 wt% concentration STF relative to the neat Twaron. Also, with the increase of the PEG's molecular weight in Twaron fabrics impregnated with 15 and 25 wt% concentration STFs, the QS puncture resistance of Twaron fabrics improved considerably, but it didn't change too much in the Twaron fabric impregnated with 35 wt% concentration STF.

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In nanotube-based polymeric composite structures it is anticipated that high damping can be achieved by taking advantage of the interfacial friction between the nanotubes and the polymer. The purpose of this paper is to investigate the structural damping characteristics of polymeric composites containing carbon nanotubes (CNT) of various kinds and amounts. The damping characteristics of the specimens with 0, 0.5, 1 and 1.5 wt% nanotube contents were determined experimentally. Through comparing with neat resin specimens, the study showed that one can enhance damping by adding CNT fillers into epoxy. It is also shown that single-walled carbon nanotube (SWCNT)-based composites could achieve higher damping than composites with multi-walled carbon nanotube (MWCNT) fillers. Comparing the damping ratio of 0.5 wt% MWCNT and functionalized MWCNT (MWCNT-COOH) specimens, the damping ratio of the 0.5 wt% MWCNT-COOH specimen is higher because of the surface modification.Similarly, experiments showed that the maximum value of the damping ratio was obtained at 1 wt%.

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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.