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Carbon fiber reinforced plastics (CFRP) bear a high potential in terms of electrical conductivity and its potential applications. A locally resolved electrical measurement method for these anisotropic materials is a key prerequisite for understanding the structural and manufacturing process-related interrelationships. The aim of this paper is to develop a measurement method that allows this to be achieved and also to investigate areas of overmolded metal contact pins in detail. CFRP samples with polyamide 6 and polycarbonate matrices were used, which were produced by using a custom-designed injection mold. In order to evaluate the measurement results and to correlate them to process related structural properties, reflected light microscopy and X-ray microtomography were used. Typical areas with significant fiber structures of assembly injection molded samples were electrically and structurally characterized to identify correlations. Among further results, the correlation of equipotential lines, acquired from the electrical analysis, with specific fiber orientations within the injection molded samples was demonstrated, fiber-poor areas were identified, and a beneficial influence of weld lines on contact resistances was determined. [ABSTRACT FROM AUTHOR]

A new class of single walled carbon nanotubes (SWCNT)/epoxy resin ink in dimethylacetamide is successfully printed using a piezo-driven jet valve dispensing system for the fabrication of flexible nanocomposites. The optimised ink prepared by solution mixing method with a viscosity (28.54 mPa⋅s), surface tension (31.3 mN/m), density (0.964 g/cm3), and 0.25 wt% SWCNT is obtained through design-of-experiments. The optimisation process is carried out focusing on the ink ejectability and the electrical properties of the resulting nanocomposites. An investigation of the electrical properties of the printed structures on glass and paper substrates is performed by analysing their sheet resistances. The resulting nanocomposite exhibits sheet resistances of 15 × 102 kΩ/sq and 0.11 kΩ/sq printed on glass and paper, respectively. Finally, the interlaminar fracture properties of the nanocomposites when integrated into glass fiber reinforced polymers are investigated. The median change of the energy release ratio GII,c is about 3%, with almost constant standard deviation.

A new class of single walled carbon nanotubes (SWCNT)/epoxy resin ink in dimethylacetamide is successfully printed using a piezo-driven jet valve dispensing system for the fabrication of flexible nanocomposites. The optimised ink prepared by solution mixing method with a viscosity (28.54 mPa⋅s), surface tension (31.3 mN/m), density (0.964 g/cm3), and 0.25 wt% SWCNT is obtained through design-of-experiments. The optimisation process is carried out focusing on the ink ejectability and the electrical properties of the resulting nanocomposites. An investigation of the electrical properties of the printed structures on glass and paper substrates is performed by analysing their sheet resistances. The resulting nanocomposite exhibits sheet resistances of 15 × 102 kΩ/sq and 0.11 kΩ/sq printed on glass and paper, respectively. Finally, the interlaminar fracture properties of the nanocomposites when integrated into glass fiber reinforced polymers are investigated. The median change of the energy release ratio GII,c is about 3%, with almost constant standard deviation. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced plastics (CFRP) bear a high potential in terms of electrical conductivity and its potential applications. A locally resolved electrical measurement method for these anisotropic materials is a key prerequisite for understanding the structural and manufacturing process-related interrelationships. The aim of this paper is to develop a measurement method that allows this to be achieved and also to investigate areas of overmolded metal contact pins in detail. CFRP samples with polyamide 6 and polycarbonate matrices were used, which were produced by using a custom-designed injection mold. In order to evaluate the measurement results and to correlate them to process related structural properties, reflected light microscopy and X-ray microtomography were used. Typical areas with significant fiber structures of assembly injection molded samples were electrically and structurally characterized to identify correlations. Among further results, the correlation of equipotential lines, acquired from the electrical analysis, with specific fiber orientations within the injection molded samples was demonstrated, fiber-poor areas were identified, and a beneficial influence of weld lines on contact resistances was determined.

Vector group of power transformers is a key element for several operational situations involving power transformers. Parallel operation of power transformers is not possible unless all transformers connected in parallel have the same vector group, among other conditions. Differential protection of power transformers has to be adjusted to consider the phase displacement corresponding to the vector group. Although vector group is a parameter guaranteed by the manufacturer and mentioned on the transformer name plate, in practice could be necessary to verify it before the transformer is put in service. If a transformer is manufactured with a specific vector group, if used in power systems with reverse phase sequence, then the resulting vector group is different, which can have important design and operational consequences. [ABSTRACT FROM AUTHOR]

Abstract The article presents a hardware and software system used for functional testing of NAND-memory chips based on FPGA. The system's module structure allows simultaneous testing of up to 144 memory chips. The system performs testing according to the predetermined algorithms and allows controlling time characteristics of NAND-memory integrated circuits. The developed software is used to tune and control the process of testing according to the user's needs, and to analyze the obtained data. Validation is performed using a NAND testing commercial system. The results of testing trial batches of multi-chip NAND-memory modules are presented. [ABSTRACT FROM AUTHOR]