Conference Papers (KET)
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Item Stretchability of Printed Conductive Structures for Thermoformable Structural Electronics(IEEE, 2024) Urban, Adam; Pretl, Silvan; Janda, MartinIn this paper, the methodology for stretchability and thermoformability of printable conductive materials is developed. Thermoforming is the process of heating materials to their softening temperatures, followed by shaping over a mold. To examine and understand the stretching of foil during the thermoforming process, variable geometry of mold is proposed. The graphical grid is applied on a polycarbonate foil, and its deformation is evaluated. Based on these results, deformation of foil can be observed. After that, using the same method, the stretchability of various conductive printed electronics materials is observed its usability is evaluated.
Item Semi-Automated Havriliak-Negami Analysis for the Investigation of Nanocomposite Properties(AIP Publishing, 2024) Michal, Ondřej; Hornak, Jaroslav; Mentlík, VáclavThe complex permittivity of materials is a critical parameter in material diagnosis, as it describes their reaction to AC voltage. Researchers often use techniques such as the Cole-Cole diagram or the Havriliak-Negami equation to determine the frequency-dependence of complex permittivity. However, the interpretation of the Cole-Cole diagram can be challenging due to the overlapping contributions of multiple relaxation processes. In contrast, the Havriliak-Negami equation provides a more accurate and detailed characterization of the dielectric properties of amorphic materials. This paper presents a simple semi-automated application of the Havriliak-Negami equation to evaluate the influence of nanoscale fillers on the properties of polyester-imide resins. Nanocomposites, which are composite materials in which one or more components have a nanoscale dimension, are promising candidates for a wide range of applications due to their ability to significantly enhance the electrical, mechanical, and thermal properties of polymers. In this study, the researchers examined the influence of nanoscale fillers on the electrical properties of polyester-imide resins, which are commonly used as insulating materials in electrical rotating machines. The analysis presented in this paper provides an alternative indicator of the practical applications of nanocomposite dielectric materials. By examining the material in an unconventional manner, researchers can obtain new insights into their electrical properties and their potential for use in electrical rotating machines. The development of new dielectric composite materials can contribute to the improvement of the performance and efficiency of electrical machines, which is essential for the transition to a low-carbon energy system.Item Influence of ZnO Nanofillers on the Permittivity of New Cold-Curing Class Polyurethanes(AIP Publishing, 2024) Hardoň, Štefan; Kúdelčík, Jozef; Hockicko, Peter; Hornak, Jaroslav; Zahoran, MiroslavAn important group of polymers with a wide range of applications is polyurethanes (PUR). In this contribution two-component system (2K PUR) is used to describe the effect of filler ZnO (Zinc Oxide) on the dielectric properties of industrial polyurethane marked as VUKOL N22 (from VUKI a.s.). From the results of the investigations carried out, it is evident that the incorporation of ZnO a decrease of real permittivity was observed due to a lower mobility of polymer chains connected to nanoparticles. Lower dielectric losses are associated with the lower relative permittivity. The SEM pictures show the distribution nanoparticles in matrix. Temperature-related relaxation peaks were observed in dissipation factor frequency spectra. Scanning Electron Microscopy (SEM) was used to measure the size and distribution of dispersed particles, and Energy Dispersive X-ray (EDX) analysis was used to confirm the chemical nature of particles.Item Estimation of Remaining Useful Life and Failure Probability of an Electrical Machine-Case Study(IEEE, 2023) Leffler, Jan; Trnka, PavelItem Bayesian Experiment Design for the Development of an Epoxy Resin Degradation Model(IEEE, 2023) Leffler, Jan; Kaska, Jan; Trnka, Pavel; Šmídl, VáclavItem The Behavior of Cold-Curing Resin after Thermal and UV Radiation Exposures(American Institute of Physics Inc., 2023) Hornak, Jaroslav; Trnka, Pavel; Prosr, Pavel; Michal, Ondřej; Kopřiva, Jiří
Item Influence of Prolonged Mixing of Silicon Dioxide Nanoparticles on the Electrical Properties of Resin Nanocomposites(American Institute of Physics Inc., 2023) Michal, Ondřej; Mentlík, Václav; Hornak, JaroslavItem New Approach In Designing Hexagonal-Shaped Antenna Based On Area Analysis(IEEE, 2022) Siahkamari, Hesam; Jahanbakhshi, Maryam; Lotfi, SaeedehItem Characterisation of Polyurethane Potting Compounds with Semiconductive Coating for Explosive Atmosphere Applications(IEEE, 2022) Kalaš, David; Kadlec, Petr; Pretl, Silvan; Soukup, Radek; Polanský, RadekItem The Effect of Various Flame Retardants on Thermal Properties of Cable Insulation(IEEE, 2022) Prosr, Pavel; Polanský, Radek; Chudoba, V.; Leńczyk, LukášItem Electrical Strength Tests of a Self-healable Copolymer Based on Ethylene and Anisylpropylene(IEEE, 2022) Nikolić, Valentino; Kadlec, Petr; Polanský, Radek; Nishiura, Masayoshi; Hou, ZhaominItem Real-Life Functional Tests of Conductive Joints of SMD Components on E-Textiles(IEEE, 2022) Hirman, Martin; Hamerník, Karel; Kalaš, David; Navrátil, Jiří; Moravcová, Daniela; Steiner, FrantišekItem Behaviour of printed resistors compatible with thick film copper technology(IEEE, 2022) Hlína, Jiří; Řeboun, Jan; Hamáček, AlešItem New Approach In Designing Hexagonal-Shaped Antenna Based On Area Analysis(Fakulta elektrotechnická ZČU, 2022) Siahkamari, Hesam; Jahanbakhshi, Maryam; Lotfi, Saeedeh; Pinker, JiříItem Textile Sensor for Skin Hydration Measurement(IEEE, 2022) Balabán, Jan; Blecha, TomášThis paper deals with the design and realization of capacitive textile sensors for skin hydration measurement. Skin hydration level is an important parameter for the healthy condition of the body and is also often used in dermatology and cosmetology. Many commercial devices are known for measuring skin hydration, which is mainly determined by medical doctors but is not suitable for longterm patient monitoring. For this reason, textile sensors and wearable evaluation electronic units were designed and created. The result is a wearable system including a textile sensor that can be easily integrated into clothes for better patient comfort. Skin hydration level is calculated based on measured sensor capacity. Obtained results will be useful for the following research on in-home care and smart textile.Item Higher Temperature Washing of Electrically Connected SMD Components onto the Textile Ribbons(IEEE, 2022) Hirman, Martin; Navrátil, Jiří; Steiner, František; Hamáček, AlešThis article addresses the higher temperature washing reliability research of interconnection technique for mounting SMD (surface mounted device) components onto conductive stretchable textile ribbons. It can be concluded that both tested interconnection technologies (i.e. low-temperature soldering and adhesive bonding) have some pros and cons, and both technologies are usable for dedicated applications. The results for soldered samples are better and stable for both tested washing temperatures 60°C and 92°C and are suitable especially for power supply applications or heating. The adhesive bonded joints have acceptable results only for 60°C washing temperature and are suitable for sensors, illumination, data transfer applications, or components with multiple leads. The research also shows that prepared joints have higher endurance than the whole ribbon.Item Analysis and Sintering Optimization of Nanoparticle Paste with High Silver Content(IEEE, 2022) Michal, David; Janda, Martin; Řeboun, JanThis paper deals with analysis, testing, and process optimization of new nanoparticle silvering paste with high silver content. Specifically, on ceramic substrates with printed conductive patterns created by thick film technology. Sintering is currently one of the most anticipated ways of connecting dies on substrates in power electronics field. Using ceramic substrates in combination with printed patterns brings out new challenges because of porous structure and ceramic specific attributes, especially when using presureless sintering as in this case. Presented paper is focused on analysis and comparison of structure and behaviour of the new nanoparticle paste with commercially available silver sintering pastes. Following step was initial testing with different deposition techniques and development of optimal sintering profile. After sintering examinations were also carried out. Shear test showing mechanical resilience, x-ray scanning for analysis of internal structure and stereoscopic analysis of sintered paste. Prolonging the temperature peak from 45 to 60 minutes and rising its temperature to 280°C shows better results in created joint. Higher shear strength was achieved together with more homogenous sintered structure. Lower porosity and presence of nanoparticles shows great potential for more homogenous, stable, and more resistive connection to mechanical separation.Item Method of Connecting Printed and Embroidered Conductive Paths in Smart Textiles(IEEE, 2022) Janda, Martin; Rostás, Kateřina; Pretl, Silvan; Řeboun, JanThis paper proposes a method of connecting conductive paths realized by embroidering and printing in smart textiles. The embroidering of conductive threads offers great electrical conductivity and the level of integration while technologies of printed electronics offer the realization of fine details. Connection is realized by overstitch of the printed contact pad. The durability of the connection is further improved with overprinting with conductive paste and encapsulation by lamination. Contact resistance and its change during the cyclic mechanical stress test and thermal shock test is measured. The proposed connection shows reliability during the thermal shock test as contact resistance is not affected. Also, during the cyclic mechanical stress test, the reliability and durability are observed.Item Embroidered Flexible Elastic Textile Antenna as Strain Sensor(IEEE, 2022) Radouchová, Michaela; Suchý, Stanislav; Blecha, TomášThis paper is focused on the design and testing of embroidered flexible elastic textile antennas for strain sensing based on the evaluation of changes in their electrical parameters. Samples of planar textile antennas for strain sensing were prepared by embroidered technology on elastic fabric. Antennas were of different shapes as split-ring resonators in 2 widths, bow tie, dipole, and as embroidery styles were chosen outline, meander, crossing. Conductive patterns were embroidered with hybrid threads containing polyester fibers and silver-coated copper wires. The stretching of the embroidered antennas was performed in one direction with a step of 10 mm on the stretching jig to their possible maximum. Results show that the resonant frequency decreases with increasing elongation for some antenna samples; it depends on the shape and embroidery style of the designed samples. Contour embroidery style shows a much better dependence on stretching in comparison with the crossing style.
