Effect of Filler Synergy and Cast Film Extrusion Parameters on Extrudability and Direction-Dependent Conductivity of PVDF/Carbon Nanotube/Carbon Black Composites

In the present study, melt-mixed composites based of poly (vinylidene fluoride) (PVDF) and fillers with different aspect ratios (carbon nanotubes (CNTs), carbon black (CB)) and their mixtures in composites were investigated whereby compression-molded plates were compared with melt-extruded films. The processing-related orientation of CNTs with a high aspect ratio leads to direction-dependent electrical and mechanical properties, which can be reduced by using mixed filler systems with the low aspect ratio CB. An upscaling of melt mixing from small scale to laboratory scale was carried out. From extruded materials, films were prepared down to a thickness of 50 µm by cast film extrusion under variation of the processing parameters. By combining CB and CNTs in PVDF, especially the electrical conductivity through the film could be increased compared to PVDF/CNT composites due to additional contact points in the sample thickness. The alignment of the fillers in the two directions within the films was deduced from the differences in electrical and mechanical film properties, which showed higher values in the extrusion direction than perpendicular to it.

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Experimental Comparison of Two Degrees-of-Freedom Vortex-Induced Vibration on High and Low Aspect Ratio Cylinders with Small Mass Ratio

Journal of Vibration and Acoustics ◽

10.1115/1.4006755 ◽

2012 ◽

Vol 134 (6) ◽

Cited By ~ 13

Author(s):

Rodolfo T. Gonçalves ◽

Guilherme F. Rosetti ◽

André L. C. Fujarra ◽

Guilherme R. Franzini ◽

César M. Freire ◽

...

Keyword(s):

Aspect Ratio ◽

Degrees Of Freedom ◽

Small Mass ◽

Experimental Comparison ◽

Small Scale ◽

Mass Ratio ◽

Vortex Induced Vibration ◽

Two Degrees Of Freedom ◽

Low Aspect Ratio ◽

Aspect Ratios

Vortex-induced motion (VIM) is a specific way for naming the vortex-induced vibration (VIV) acting on floating units. The VIM phenomenon can occur in monocolumn production, storage and offloading system (MPSO) and spar platforms, structures presenting aspect ratio lower than 4 and unity mass ratio, i.e., structural mass equal to the displaced fluid mass. These platforms can experience motion amplitudes of approximately their characteristic diameters, and therefore, the fatigue life of mooring lines and risers can be greatly affected. Two degrees-of-freedom VIV model tests based on cylinders with low aspect ratio and small mass ratio have been carried out at the recirculating water channel facility available at NDF-EPUSP in order to better understand this hydro-elastic phenomenon. The tests have considered three circular cylinders of mass ratio equal to one and different aspect ratios, respectively L/D = 1.0, 1.7, and 2.0, as well as a fourth cylinder of mass ratio equal to 2.62 and aspect ratio of 2.0. The Reynolds number covered the range from 10 000 to 50 000, corresponding to reduced velocities from 1 to approximately 12. The results of amplitude and frequency in the transverse and in-line directions were analyzed by means of the Hilbert-Huang transform method (HHT) and then compared to those obtained from works found in the literature. The comparisons have shown similar maxima amplitudes for all aspect ratios and small mass ratio, featuring a decrease as the aspect ratio decreases. Moreover, some changes in the Strouhal number have been indirectly observed as a consequence of the decrease in the aspect ratio. In conclusion, it is shown that comparing results of small-scale platforms with those from bare cylinders, all of them presenting low aspect ratio and small mass ratio, the laboratory experiments may well be used in practical investigation, including those concerning the VIM phenomenon acting on platforms.

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Direction Dependent Electrical Conductivity of Polymer/Carbon Filler Composites

Polymers ◽

10.3390/polym11040591 ◽

2019 ◽

Vol 11 (4) ◽

pp. 591 ◽

Cited By ~ 7

Author(s):

Karina Kunz ◽

Beate Krause ◽

Bernd Kretzschmar ◽

Levente Juhasz ◽

Oliver Kobsch ◽

...

Keyword(s):

Carbon Nanotubes ◽

Electrical Conductivity ◽

Multiwalled Carbon Nanotubes ◽

Vinylidene Fluoride ◽

Extrusion Direction ◽

Filler Concentration ◽

Multiwalled Carbon ◽

Carbon Filler ◽

Aspect Ratios ◽

Extruded Films

The method of measuring electrical volume resistivity in different directions was applied to characterize the filler orientation in melt mixed polymer composites containing different carbon fillers. For this purpose, various kinds of fillers with different geometries and aspect ratios were selected, namely carbon black (CB), graphite (G) and expanded graphite (EG), branched multiwalled carbon nanotubes (b-MWCNTs), non-branched multiwalled carbon nanotubes (MWCNTs), and single-walled carbon nanotubes (SWCNTs). As it is well known that the shaping process also plays an important role in the achieved electrical properties, this study compares results for compression molded plates with random filler orientations in the plane as well as extruded films, which have, moreover, conductivity differences between extrusion direction and perpendicular to the plane. Additionally, the polymer matrix type (poly (vinylidene fluoride) (PVDF), acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6)) and filler concentration were varied. For the electrical measurements, a device able to measure the electrical conductivity in two directions was developed and constructed. The filler orientation was analyzed using the ratio σin/th calculated as in-plane conductivity σin-plane (σin) divided by through-plane conductivity σthrough-plane (σth). The ratio σin/th is expected to increase with more pronounced filler orientation in the processing direction. In the extruded films, alignment within the plane was assigned by dividing the in-plane conductivity in the extrusion direction (x) by the in-plane conductivity perpendicular to the extrusion direction (y). The conductivity ratios depend on filler type and concentration and are higher the higher the filler aspect ratio and the closer the filler content is to the percolation concentration.

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Investigations on the Effect of Aspect Ratio Into the Performance of Savonius Rotors

ASME 2013 Gas Turbine India Conference ◽

10.1115/gtindia2013-3729 ◽

2013 ◽

Cited By ~ 3

Author(s):

Sukanta Roy ◽

Ujjwal K. Saha

Keyword(s):

Aspect Ratio ◽

Wind Energy ◽

Wind Turbine ◽

Vertical Axis ◽

Maintenance Cost ◽

Small Scale ◽

Low Speed ◽

Aspect Ratios ◽

Gap Ratio ◽

Overlap Ratio

With the rapid execution in the renewable energy field, vertical axis wind turbines are finding its application in the small-scale distributed wind energy generation, particularly in rural areas. The Savonius rotor is a drag based vertical axis wind turbine and is used as a small-scale wind energy converter with low installation and maintenance cost. These rotors are simple in design, easy to assemble and can be operated at low-speed wind from any direction. However, these rotors are not gaining popularity because of its low efficiency and improper design. The aspect ratio (height to diameter of the rotor) is one of the very important factors for designing a suitable small-scale wind turbine. The other important factors include overlap ratio, gap ratio and blade profile of the rotor. In the present investigation, a number of rotor models with different aspect ratios are tested in a low speed wind tunnel with open test section facility. The effects of overlap ratio and gap ratio are also studied keeping the rotor height to be the same. The wind speed is varied from 5–10 m/s. To estimate the performance of these rotors, electrical loads are given with respect to different wind speeds and the power output is calculated in terms of voltage and current. The results depicted an optimum aspect ratio of 0.80, which can be used to improve the performance of Savonius rotors.

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Dispersion of Layered Organosilicates in Isobutylene-Based Elastomers

Rubber Chemistry and Technology ◽

10.5254/1.3547938 ◽

2006 ◽

Vol 79 (2) ◽

pp. 281-306 ◽

Cited By ~ 12

Author(s):

Andy H. Tsou ◽

Matthew B. Measmer

Keyword(s):

Aspect Ratio ◽

Carbon Black ◽

Layered Silicate ◽

Tertiary Amines ◽

Aspect Ratios ◽

Silicate Nanocomposites ◽

Dispersion State ◽

Planar Orientation ◽

Internal Mixer ◽

Better Than

Abstract Dispersion morphologies of polymer-layered silicate nanocomposites based on either brominated poly(isobutylene-co-para-methylstyrene), BIMSM, or brominated poly(isobutylene-co-isoprene), BIIR, and an organosilicate, dimethylditallow ammonium-exchanged montmorillonite, Cloisite™ 6A, with and without N660 carbon black fillers were examined using SAXS, WAXS, AFM, and TEM. These compounds were prepared using an internal mixer and cured for property measurements. Due to the observed partial orientation of organosilicates and their possible heterogeneous intercalation, degrees of exfoliation and dispersion of organosilicates in BIMSM and BIIR were unable to be characterized and quantified simply by TEM, AFM, or SAXS alone. Instead, using the projected aspect ratio of organosilicates in BIMSM or BIIR, extracted from Gusev-Lusti equation based on measured permeability ratios, was found to provide a relative measure of their dispersion state. Since better dispersion, higher planar orientation, and/or increasing extent of exfoliation lead to higher aspect ratio, this calculated aspect ratio was used as a measure of organosilicate dispersion in BIMSM and BIIR compounds. According to experimentally extracted projected aspect ratios, it was found that BIMSM disperses organosilicates better than BIIR and that carbon black filler does not affect the organosilicate dispersion in BIMSM. Addition of tertiary amines in BIMSM enhances the dispersion of organosilicates, possibly through favorable interactions between organosilicates and quaternary ammonium functionalized BIMSM, resulting in further reduction in permeability.

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Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part III: Results of Supplementary and UTQG Treadwear Test Series

Tire Science and Technology ◽

10.2346/1.2148776 ◽

1986 ◽

Vol 14 (4) ◽

pp. 235-263

Author(s):

A. G. Veith

Keyword(s):

Carbon Black ◽

Comprehensive Evaluation ◽

Work Intensity ◽

Generic Type ◽

Aspect Ratios ◽

Index Variation ◽

Primary Determinant ◽

Severity Levels ◽

High Test ◽

Better Than

Abstract The effect of tread compound variation on tire treadwear was studied using bias and radial tires of two aspect ratios. Compound variations included types of rubber and carbon black as well as the levels of carbon black, process oil, and curatives. At low to moderate test severity, SBR and an SBR/BR blend performed better than NR while at high test severity NR and SBR were better than the SBR/BR blend. The SBR/BR blend was the best at low severity testing. Higher structure and higher surface area carbon black gave improved treadwear at all severity levels. The concept of a “frictional work intensity” as the primary determinant of treadwear index variation with test severity is proposed. Some factors which influence frictional work intensity are discussed.

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Effects of Steel Fiber Percentage and Aspect Ratios on Fresh and Harden Properties of Ultra-High Performance Fiber

Applied Mechanics ◽

10.3390/applmech2030028 ◽

2021 ◽

Vol 2 (3) ◽

pp. 501-515

Author(s):

Rajib Kumar Biswas ◽

Farabi Bin Ahmed ◽

Md. Ehsanul Haque ◽

Afra Anam Provasha ◽

Zahid Hasan ◽

...

Keyword(s):

Mechanical Properties ◽

Aspect Ratio ◽

High Performance ◽

Steel Fiber ◽

Setting Time ◽

Fiber Reinforced Concrete ◽

Future Research ◽

Manufacturing Cost ◽

Aspect Ratios ◽

High Performance Fiber

Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers to understand the distinctive characteristics of UHPFRC.

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Surface Texturing of Si with Periodically Arrayed Oblique Nanopillars to Achieve Antireflection

Materials ◽

10.3390/ma14020380 ◽

2021 ◽

Vol 14 (2) ◽

pp. 380

Author(s):

Jun-Hyun Kim ◽

Sanghyun You ◽

Chang-Koo Kim

Keyword(s):

Aspect Ratio ◽

Plasma Etching ◽

Surface Texturing ◽

Light Reflection ◽

Si Substrate ◽

Weighted Mean ◽

Optical Reflectance ◽

Si Substrates ◽

Aspect Ratios ◽

Shadowing Effect

Si surfaces were texturized with periodically arrayed oblique nanopillars using slanted plasma etching, and their optical reflectance was measured. The weighted mean reflectance (Rw) of the nanopillar-arrayed Si substrate decreased monotonically with increasing angles of the nanopillars. This may have resulted from the increase in the aspect ratio of the trenches between the nanopillars at oblique angles due to the shadowing effect. When the aspect ratios of the trenches between the nanopillars at 0° (vertical) and 40° (oblique) were equal, the Rw of the Si substrates arrayed with nanopillars at 40° was lower than that at 0°. This study suggests that surface texturing of Si with oblique nanopillars reduces light reflection compared to using a conventional array of vertical nanopillars.

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Strength Analysis of Alternative Airframe Layouts of Regional Aircraft on the Basis of Automated Parametrical Models

Aerospace ◽

10.3390/aerospace8030080 ◽

2021 ◽

Vol 8 (3) ◽

pp. 80

Author(s):

Dmitry V. Vedernikov ◽

Alexander N. Shanygin ◽

Yury S. Mirgorodsky ◽

Mikhail D. Levchenkov

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

High Performance ◽

Strength Analysis ◽

Labor Input ◽

Aerodynamic Loading ◽

Aspect Ratios ◽

Wide Range ◽

Parametrical Design

This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.

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Influence of nozzle exit geometrical parameters on supersonic jet decay

International Journal of Turbo and Jet Engines ◽

10.1515/tjeng-2020-0047 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Prasanta Kumar Mohanta ◽

B. T. N. Sridhar ◽

R. K. Mishra

Keyword(s):

Aspect Ratio ◽

Nozzle Exit ◽

Ambient Air ◽

Schlieren Image ◽

Geometrical Parameters ◽

Image Study ◽

Aspect Ratios ◽

Core Length ◽

Supersonic Core Length ◽

The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

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Aspect Ratio Driven Relationship between Nozzle Internal Flow and Supersonic Jet Mixing

Aerospace ◽

10.3390/aerospace8030078 ◽

2021 ◽

Vol 8 (3) ◽

pp. 78

Author(s):

Kalyani Bhide ◽

Kiran Siddappaji ◽

Shaaban Abdallah

Keyword(s):

Boundary Layer ◽

Aspect Ratio ◽

Nozzle Exit ◽

Supersonic Jet ◽

Internal Flow ◽

Shear Stresses ◽

Loss Mechanism ◽

Potential Core ◽

Jet Mixing ◽

Aspect Ratios

This work attempts to connect internal flow to the exit flow and supersonic jet mixing in rectangular nozzles with low to high aspect ratios (AR). A series of low and high aspect ratio rectangular nozzles (design Mach number = 1.5) with sharp throats are numerically investigated using steady state Reynolds-averaged Navier−Stokes (RANS) computational fluid dynamics (CFD) with k-omega shear stress transport (SST) turbulence model. The numerical shadowgraph reveals stronger shocks at low ARs which become weaker with increasing AR due to less flow turning at the throat. Stronger shocks cause more aggressive gradients in the boundary layer resulting in higher wall shear stresses at the throat for low ARs. The boundary layer becomes thick at low ARs creating more aerodynamic blockage. The boundary layer exiting the nozzle transforms into a shear layer and grows thicker in the high AR nozzle with a smaller potential core length. The variation in the boundary layer growth on the minor and major axis is explained and its growth downstream the throat has a significant role in nozzle exit flow characteristics. The loss mechanism throughout the flow is shown as the entropy generated due to viscous dissipation and accounts for supersonic jet mixing. Axis switching phenomenon is also addressed by analyzing the streamwise vorticity fields at various locations downstream from the nozzle exit.

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