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Moisture absorption characteristics and effects on mechanical properties of Kolon/epoxy composites
Obradović Vera,Simić Danica,Sejkot Petr,Machalická Klára V.,Vokáč Miroslav 한국물리학회 2021 Current Applied Physics Vol.26 No.-
Para-aramid fibers (Kolon) are high performance polymeric fibers characterized by their high tenacity and impact resistance. They are used for the soft body armor structures in ballistics. In this study, the testing specimens were made from multilayered Kolon fabrics impregnated with epoxy resin where silicon carbide (SiC) microparticles or SiC nanofibers were added as reinforcement. The laminated composite samples were fabricated by hot compression and curing of epoxy resin. The tensile and impact strengths of the untreated specimens were compared with the ones that underwent water absorption in duration of 72 h (immersion or humidity) followed by desorption. The immersion of the specimens in water and exposure to high humidity (70%) were performed according to the ISO 62 standard while the tensile test was carried out in accordance with the ASTM D 3039 standard. In the end, the tensile test simulation of the laminated composite by using software Abaqus® was accomplished.
Vera Obradović,Danica Simić,Milorad Zrilić,Dušica B. Stojanović,Petar S. Uskoković 한국섬유공학회 2021 Fibers and polymers Vol.22 No.2
Multilayered composites based on aramid fabrics are widely used in impact protection. The objective of this studyis creating a new kind of multiaxial aramid fabric composites with inorganic fullerene-like tungsten disulfide nanoparticles(IF-WS2) and single walled carbon nanotubes (SWCNT) used as nanoreinforcement to enhance the dynamic mechanical andanti-stabbing properties of the composites. The four composites of the Kolon fabric forms were impregnated with 10 wt.%poly(vinyl butyral) (PVB)/ethanol solution which contained different forms of IF-WS2 nanoparticles. The surfaces of IF-WS2were coated with silane coupling agent (m-IF) and the SWCNT were oxidized (o-SWCNT) for the fabrication of the o-SWCNT/m-IF hybrid nanoparticles. The mechanical testing showed that the Kolon/PVB/o-SWCNT/m-IF sample producednearly 62 % of improvement in the tensile strength and 51 % of improvement in the tensile energy absorption compared tothe Kolon/PVB sample. Furthermore, the sample with the o-SWCNT/m-IF hybrid nanoparticles demonstrated 24 % ofenhancement in the impact toughness and 48 % of improvement in the absorbed energy after knife penetration in comparisonwith the Kolon/PVB sample.
Temperature Sensors Manufactured from Edible Materials Intended for Oral Cavity Operation
Goran M. Stojanović,Milan Radovanović,Sanja Kojić,Lazar Milić,Mitar Simić,Naturality Company,Raphael Georges Duval,Jelena Vukmirović,Bojan Petrović 한국정밀공학회 2024 International Journal of Precision Engineering and Vol.11 No.1
Following the circular economy concept, all areas of science, including electronics, require individual approach. The green electronics approach implies processing natural based materials for development of electronic components even for single use, so that waste does not exist. This paper describes the production of thermistors from 3 different types of edible materials, their testing in laboratory conditions, as well as the application for measuring the temperature in the human oral cavity. To make the thermistor, three types of natural materials were used (carrageenan, polyvinyl alcohol and apple pomace-based). After fabrication, materials were poured into molds. Aluminium foil contacts were placed so that the electrical characterization of the materials could be performed. Several parameters were measured: resistance (R), impedance (Z) and the phase angle (θ) as a function of frequency. In order to determine whether the thermistors have a positive or negative temperature coefficient and to determine their sensitivity, measurements were conducted at three different temperatures: 25 ℃ (room temperature), 37 ℃ (human body temperature), and 50 ℃. The thermistors demonstrated negative temperature coefficient behaviour. Additionally, it was demonstrated that the apple pomace-based thermistor can successfully measure healthy volunteer's temperature.
STUDY OF ROTATIONAL BAND STRUCTURE OF EVEN-EVEN 132;134SM NUCLEI
ARUN GUPTA,SURBHI GUPTA,SIMI GUPTA,SURAM SINGH,ARUN BHARTI 장전수학회 2021 Proceedings of the Jangjeon mathematical society Vol.24 No.4
The study of neutron-decient nuclei in the A130 mass region has been an interesting subject in nuclear structure physics as this region is considered to be transitional region. In the present work, the positive parity rotational band structure of even-even 132,134Sm up to the high spin states has been studied in a microscopic frame work of calculations known as Projected Shell Model (PSM). Yrast spectra for 132,134Sm have been obtained from the PSM calculations and has been found to be in good agreement with the available experimental data. Besides this, the present calculations have also reported the occurrence of back bending at the same spins at which experimental data shows in both the nuclei.