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1

Thermal stability of the elastomeric anti-trauma pad

100%

Olszewska K. , Zielinska D. , Struszczyk M. H. , Wierzbicki Ł. , Leonowicz M. K.

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tom Vol. 19, nr 2

93--100

EN

The elastomeric anti-trauma pad (EA-TP) based on shear thickening fluid (STF) has been developed. Dynamic oscillatory shear experiment was conducted at constant strain amplitude of 5%. STF composed of 25% of volume fraction of 7 nm Fumed Silica, dispersed in polypropylene glycol with molar mass 400 gmol−1 shows elastic properties in entire investigated range of the frequency. Ballistic tests of EA-TP with 7.62 mm × 39 mm PS bullets were performed according to the PN-V-87000:2011 standard. The studies revealed about 60% reduction of the average backface signature depth (BSD) for the EA-TP, when compared to the nowadays commonly used soft insert. The ATR-FTIR analysis confirmed slight impact of the elevated temperature and air (oxygen) on the chemical degradation of the EA-TP surface. The UV-VIS spectroscopy has allowed to notice colour deviation of the aged samples towards green and yellow, as well as lack of dye resistance to accelerated aging process. Thermographic analysis has shown no visible changes of the EA-TP surface and sub-surface during accelerated aging process. The aforementioned small changes on the surface of EA-TP did not affect the ballistic properties of composite armour. EA-TP insert maintains ballistic properties after accelerated aging process which was simulating the period of 6 years according to ASTM F1980 – 07:2002 standard.

2

Deceleration behavior of multi‑layer cork composites intercalated with a non‑Newtonian material

75%

Sheikhi M. R. , Gürgen S.

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tom Vol. 23, no. 1

art. no. e2, 2023

EN

Impact or sudden accelerations are strictly avoided by sensitive systems such as electronic devices, robotic structures and unmanned aerial vehicles (UAVs). In order to protect these systems, various composites have been developed in recent years. Due to its excellent energy absorbing capabilities as well as eco-friendly and sustainable properties, cork is one of promising materials dedicated to protective applications. In this study, we beneft from cork agglomerates in multi-layer design considering its advantages such as high fexural stifnesstoweight ratio and good buckling resistance over monolithic structures. In addition, a non-Newtonian material, namely shear thickening fuid (STF) was incorporated in this design. STF shows rapid increase in its viscosity under loading and thereby enabling a stifer texture that contributes to protective performance. At rest state, STF exhibit fuidic behavior and provides fexibility for composite. In the experimental stage, deceleration behavior of these composites was investigated. According to the analyses, STF exhibits promising results to lower peak decelerations while extending time period of deceleration under impact loading. STF contribution is pronounced by using this material in a closed medium such as in wrapped foam to avoid spilling out of composite during impact. The designed eco-friendly smart composites are suggested to cover internal parts in sensitive systems. Micro-mobility helmet is another prospective application area for cork/STF structures since they provide light-weight, excellent fexibility and good deceleration behavior.

3

Rheological and deformation behavior of natural smart suspensions exhibiting shear thickening properties

75%

Gürgen S. , de Sousa R. J. A.

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tom Vol. 20, no. 4

166--173

EN

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 eco-friendly 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.

4

Zastosowanie cieczy i żeli nienewtonowskich w osłonach balistycznych

63%

Tatko R. , Hoppe J.

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tom T. 2

37--42

PL

W artykule przedstawiono aktualny stan wiedzy dotyczący zastosowania cieczy nienewtonowskich w osłonach balistycznych. Szczególne znaczenie dla zastosowań balistycznych mają ciecze zagęszczane ścinaniem, dla których wraz ze wzrostem szybkości ścinania następuje nieproporcjonalnie szybszy przyrost naprężeń stycznych w cieczy. Obecne badania skupiają się na dwóch sposobach wykorzystania tych cieczy: impregnowanie miękkich osłon balistycznych wykonywanych z tkanin z włókien aramidowych czy polietylenowych oraz impregnowanie lekkich, sprężystych pianek siatkowych, o otwartych porach, wykorzystywanych jako wewnętrzna warstwa osłon balistycznych. Wyniki przeprowadzonych badań świadczą o korzystnym wpływie cieczy nienewtonowskich na właściwości balistyczne osłon.