Rheological and deformation behavior of natural smart suspensions exhibiting shear thickening properties
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(2020) 20:110
ORIGINAL ARTICLE
Rheological and deformation behavior of natural smart suspensions exhibiting shear thickening properties Selim Gürgen1 · Ricardo J. Alves de Sousa2 Received: 9 January 2020 / Revised: 17 June 2020 / Accepted: 28 August 2020 © Wroclaw University of Science and Technology 2020
Abstract Shear thickening fluid (STF) is a very interesting and promising material in several application fields where a different mechanical is demanded based on loading rates, like body armor and vibration insulators. Cork is a natural cellular material by excellence, filled with well-known beneficial effects in terms of insulation and also interesting crashworthiness properties. In this work, cork grains of very small size (0.5–1.0 mm) are added to two different shear thickening suspensions, one of them a fully natural water and cornstarch, and the other based on fumed silica and polyethylene glycol. The rheology of these ecofriendly suspensions was investigated and the influences of including cork grains were discussed. In addition, microscopic analyses were carried out to observe the deformations at each component during the shear thickening phenomenon. Cork grains reduce the load-carrying capacity in the suspensions due to the deformable characteristics of cork. For this reason, shear thickening properties are suppressed in the mixtures. Despite this, it is possible to state that viscosity increase in the mixtures leads to strong particle contacts, and thereby resulting in particle deformations in the main constituent powder as well as in the cork additives due to their softer structures. Keywords Shear thickening fluid · Rheology · Suspension · Cork
1 Introduction A shear thickening fluid (STF) is a kind of non-Newtonian suspension showing increasing viscosity under increasing loading rates. Upon removing the loading from the medium, the suspension lowers its viscosity, which means that there is a reversible process in the material. Due to this unique behavior, this smart fluid has been adapted to various engineering applications. In early studies, STF treated high performance fabrics that were tested against different threats, such as needles [1], spikes [2, 3], knives [4, 5] and projectiles [6, 7], to benefit from the shear thickening rheology for stopping the attacking threats. Although STF contributes to the protective performance of textiles, there is a complicated mechanism in STF/textile composites to clearly understand whether shear thickening rheology alone is useful for * Selim Gürgen [email protected] 1
Eskişehir Vocational School, ESOGU, Eskişehir, Turkey
TEMA, Center of Mechanical Technology and Automation, Department of Mechanical Engineering, University of Aveiro, Aveiro, Portugal
2
protection. On the other hand, STF was utilized in vibration attenuation systems to absorb vibrations by the effect of its increasing viscosity. According to previous works [8–11], STF inclusion in damping systems provides beneficial results in terms of vibration attenuation. In addition, STFs inte
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