scholarly journals DYNAMICS OF LAYER-BY-LAYER DESTRUCTION OF CARBON PLASTIC BY LIGHTNING CURRENTS: THEORY AND EXPERIMENT

2020 ◽  
pp. 67-73
Author(s):  
Igor A. Guschin
Keyword(s):  
Experimental Studies ◽  
Neumann Boundary ◽  
Aircraft Design ◽  
Carbon Plastic ◽  
Layer By Layer ◽  
Experiment Data ◽  
Conductive Medium ◽  
Transverse Current ◽  
Number Of Layers ◽  
Current Densities

On the basis of two models of lightning currents spreading on carbon plastic, the criteria of material destruction are determined. One of the models – the anisotropic conductive medium model from the Laplace equation with specified Neumann boundary conditions – makes it possible to obtain an exact solution in the form of Bessel functions for longitudinal and transverse current densities and to consider the material destruction zones by the radius and the depth. The model adequately describes the experiment with different arrangement of electrodes simulating the passage of lightning currents on constructions made of conductive composite and metal. The second – the model of composite layered structure – is constructed using the diagram of carbon plastic substitution and makes it possible to find the distribution of currents by a numerical method. The results of the calculations for both models are well consistent. The dynamics analysis of carbon plastic destruction revealed the criteria of destruction with parameters of real carbon plastic and experiment data that do not contradict the parameters of carbon plastic destruction obtained in foreign experimental studies. These criteria allow to determine the dependence between the value of the current integral and the number of layers of the composite material. Options with a small number of layers and with a large one when the reach-through breakdown criterion is possible were taken into account. Comparison of calculated and experimental destruction data showed good curve matching. The obtained criteria make it possible to predict the effects of lightning exposure under different material parameters and to take measures to improve the lightning resistance of carbon plastic products at the stage of aircraft design.

scholarly journals Dynamics and criteria of CFRP destruction by lightning currents

2021 ◽  
Vol 2124 (1) ◽  
pp. 012020
Author(s):  
I A Guschin
Keyword(s):  
Composite Material ◽  
Carbon Fiber ◽  
Neumann Boundary ◽  
Specific Weight ◽  
Design Stage ◽  
Carbon Plastic ◽  
Layer By Layer ◽  
Material Anisotropy ◽  
Large Current ◽  
Calculation Results

Abstract The article discusses a promising conductive composite material such as carbon-plastic. This material has significant strength, not inferior to metal, has a low specific weight and has interesting electrophysical characteristics. For a wider use of the material in various structural products, it is necessary to consider its unique characteristics. The work is devoted to the study of the conductive properties of carbon fiber under the influence of lightning currents and the development of criteria for its destruction. Based on two models of destruction of CFRP by lightning currents, a theoretical analysis of its destruction has been carried out. The first model considered the composite material as a continuous medium with anisotropic-conducting properties. The solution of the Laplace equation with the Neumann boundary conditions made it possible to find the distribution of current densities over the material and theoretically determine the radius and depth of damage. The second model, the layered structure model, took into account the structure of real CFRP. The dynamics of layer-by-layer destruction is considered on the basis of the equivalent circuit of carbon fiber reinforced plastic, which takes into account the longitudinal and transverse resistivity of the composite. The distributions of the radial current density along the radius and depth of the material are constructed and the analysis of the spreading of currents at various degrees of material anisotropy is carried out. Strong anisotropy, leading to the release of total energy in the first layer. Destruction of the upper layer changes the distribution of currents in the rest of the layers. The results of numerical modeling of layer-by-layer destruction of CFRP for five layers are presented. The process of destruction under the action of large current pulses is considered. The fracture criteria for various degrees of material anisotropy are obtained and refined. The resulting formulas contain values that are reproduced in the experiment. The calculation results are in good agreement with experiment. In conclusion, it is concluded that the criteria are applied to predict the effects of lightning and optimize lightning protection at the design stage of an aircraft.

Polyaniline: Influence of Polymerization Current Density

1994 ◽  
Vol 369 ◽  
Author(s):  
Steen Skaarup ◽  
L.M.W.K. Gunaratne ◽  
Keld West ◽  
Birgit Zachau-Christiansen
Keyword(s):  
Cyclic Voltammetry ◽  
Current Density ◽  
High Current Density ◽  
Electrochemical Polymerization ◽  
Regular Structure ◽  
Spectral Lines ◽  
Complex Nature ◽  
Cyclic Voltammograms ◽  
Layer By Layer ◽  
Current Densities

AbstractPolyaniline has been synthesized in propylene carbonate by galvanostatic electrochemical polymerization at current densities between 16 and 1000 μA/cm2. Earlier results for polypyrrole have shown that low and high current density films have different properties: The films synthesized at low current density have a higher conjugation length and a more regular structure. The corresponding effect in PANI has been investigated by cyclic voltammetry and UV/visible spectroscopy. Simultaneous measurement of cyclic voltammograms and the absorbtion of selected spectral lines is used because of the complex nature of the PANI system which involves several redox systems as well as forms differing in the degree of protonation and morphology.The main result is that the method of galvanostatic synthesis at low current densities (-16 μA/cm2) produces polyaniline polymers of different, more conjugated and more regular structure than those prepared at higher current densities. The standard method of in situ layer-by-layer polymerization of conducting polymers during cyclic voltammetry often results in uncontrolled and unmeasured current densities of 0.5-2 mA/cm2 which produces a film that probably has a less regular structure containing more deviations from ideality.

scholarly journals Study of non-isothermal liquid evaporation in synthetic micro-pore structures with hybrid lattice Boltzmann model

2019 ◽  
Vol 866 ◽  
pp. 33-60 ◽  
Author(s):  
Feifei Qin ◽  
Luca Del Carro ◽  
Ali Mazloomi Moqaddam ◽  
Qinjun Kang ◽  
Thomas Brunschwiler ◽  
...  
Keyword(s):  
Lattice Boltzmann ◽  
Evaporation Rate ◽  
Experimental Studies ◽  
Liquid Films ◽  
Lattice Boltzmann Model ◽  
Layer By Layer ◽  
Pore Structures ◽  
Liquid Evaporation ◽  
Cooling Effects ◽  
Boltzmann Model

Non-isothermal liquid evaporation in micro-pore structures is studied experimentally and numerically using the lattice Boltzmann method. A hybrid thermal entropic multiple-relaxation-time multiphase lattice Boltzmann model (T-EMRT-MP LBM) is implemented and validated with experiments of droplet evaporation on a heated hydrophobic substrate. Then liquid evaporation is investigated in two specific pore structures, i.e. spiral-shaped and gradient-shaped micro-pillar cavities, referred to as SMS and GMS, respectively. In SMS, the liquid receding front follows the spiral pattern; while in GMS, the receding front moves layer by layer from the pillar rows with large pitch to the rows with small one. Both simulations agree well with experiments. Moreover, evaporative cooling effects in liquid and vapour are observed and explained with simulation results. Quantitatively, in both SMS and GMS, the change of liquid mass with time coincides with experimental measurements. The evaporation rate generally decreases slightly with time mainly because of the reduction of liquid–vapour interface. Isolated liquid films in SMS increase the evaporation rate temporarily resulting in local peaks in evaporation rate. Reynolds and capillary numbers show that the liquid internal flow is laminar and that the capillary forces are dominant resulting in menisci pinned to the pillars. Similar Péclet number is found in simulations and experiments, indicating a diffusive type of heat, liquid and vapour transport. Our numerical and experimental studies indicate a method for controlling liquid evaporation paths in micro-pore structures and maintaining high evaporation rate by specific geometry designs.

scholarly journals NUMERICAL MODELING AND EXPERIMENTAL RESEARCH OF A LIQUID-LIQUID EJECTORS WITH A CURVED INITIAL MIXING CHAMBER AREA AND WITH DIRECT MIXING CAMERA

2020 ◽  
pp. 88-95
Author(s):  
Salar Kartas ◽  
◽  
Vladimir Panchenko ◽  
Yury Aleksandrov ◽  
◽  
...  
Keyword(s):  
Pressure Drop ◽  
Experimental Studies ◽  
Design Parameters ◽  
Layer By Layer ◽  
Relative Pressure ◽  
Initial Portion ◽  
Ansys Fluent ◽  
Ejection Coefficient ◽  
Mixing Chamber ◽  
Calculation Results

The article presents the results of numerical simulations and experimental studies of a liquid-liquid ejector with a curved initial portion of the mixing chamber. The experiment was conducted on liquid-liquid ejectors, models of which are made on a 3D printer, by the method of layer-by-layer deposition. The influence of possible manufacturing errors of the ejector on its characteristics is estimated. The issues of the use of liquid ejectors designed to work in the field of various predetermined ejection coefficients are considered. The theoretical ejection coefficient and the reasons for reducing the ejection coefficient in real ejectors are determined. The obtained dependences make it possible to determine the optimal design parameters of a liquid ejector and thereby increase its ejection coefficient. The relative pressure drop is shown at a low coefficient and at a high ejection coefficient. The calculated and experimental results of determining the ejection coefficient for liquid ejectors, which are widely used in various fields of technology, are presented. The results of numerical simulation of internal processes in the ANSYS-Fluent hydro-gasdynamic application package flowing in a single-phase liquidliquid ejector based on the study of a small-sized model are presented. As a result of the simulation, a good agreement was obtained between the calculation results of the model corresponding to the real prototype and the experimental data and comparison with the results of other authors. Several conclusions can be drawn from the results of the study. For example, a region of values of the ejection coefficient was found in which the relative pressure drop created by the ejector increases with an increase in the ejection coefficient.

Ge/Ag(111): SURFACE ALLOY OF A SEMICONDUCTOR ON A METAL

1999 ◽  
Vol 06 (05) ◽  
pp. 929-934 ◽  
Author(s):  
H. OUGHADDOU ◽  
B. AUFRAY ◽  
J. M. GAY
Keyword(s):  
Phase Separation ◽  
Electron Spectroscopy ◽  
Auger Electron ◽  
Room Temperature ◽  
Surface Segregation ◽  
Experimental Studies ◽  
Surface Alloy ◽  
Layer By Layer ◽  
Kinetics Of ◽  
Monolayer Coverage

We present one of the first experimental studies of the formation of an ordered surface alloy of a semiconductor, Ge, and a metal, Ag, with bulk tendency to phase separation. The kinetics of growth at room temperature as well as the surface segregation of Ge have been investigated for the (111) orientation using Auger Electron Spectroscopy (AES) and Low Electron Energy Diffraction (LEED). The growth mode of Ge on Ag(111) is layer-by-layer like up to at least two layers. An unexpected ordered surface alloy forming a [Formula: see text] superstructure is observed during the growth at 1/3 germanium monolayer, followed by a p(7× 7) superstructure at one-monolayer coverage. The surface Ge segregation studied via both dissolution and segregation kinetics shows the particular stability of the ordered [Formula: see text] surface alloy.

scholarly journals Antibacterial Multi-Layered Nanocellulose-Based Patches Loaded with Dexpanthenol for Wound Healing Applications

Nanomaterials ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2469
Author(s):  
Daniela F. S. Fonseca ◽  
João P. F. Carvalho ◽  
Verónica Bastos ◽  
Helena Oliveira ◽  
Catarina Moreirinha ◽  
...  
Keyword(s):  
Wound Healing ◽  
Mechanical Performance ◽  
In Vitro Release ◽  
Human Keratinocytes ◽  
Controlled Drug Release ◽  
Release Mechanism ◽  
Layer By Layer ◽  
Number Of Layers ◽  
Migration Capacity

Antibacterial multi-layered patches composed of an oxidized bacterial cellulose (OBC) membrane loaded with dexpanthenol (DEX) and coated with several chitosan (CH) and alginate (ALG) layers were fabricated by spin-assisted layer-by-layer (LbL) assembly. Four patches with a distinct number of layers (5, 11, 17, and 21) were prepared. These nanostructured multi-layered patches reveal a thermal stability up to 200 °C, high mechanical performance (Young’s modulus ≥ 4 GPa), and good moisture-uptake capacity (240–250%). Moreover, they inhibited the growth of the skin pathogen Staphylococcus aureus (3.2–log CFU mL−1 reduction) and were non-cytotoxic to human keratinocytes (HaCaT cells). The in vitro release profile of DEX was prolonged with the increasing number of layers, and the time-dependent data imply a diffusion/swelling-controlled drug release mechanism. In addition, the in vitro wound healing assay demonstrated a good cell migration capacity, headed to a complete gap closure after 24 h. These results certify the potential of these multi-layered polysaccharides-based patches toward their application in wound healing.

Correlation between production parameters and mechanical properties of ABS plus p430 fused deposition material

2021 ◽  
pp. 095440622110272
Author(s):  
M Corsi ◽  
S Bagassi ◽  
MC Moruzzi ◽  
L Seccia
Keyword(s):  
Mechanical Properties ◽  
Layer Thickness ◽  
Fused Deposition Modeling ◽  
Testing Machine ◽  
Experimental Studies ◽  
Deep Understanding ◽  
Layer By Layer ◽  
Fused Deposition ◽  
Production Parameters ◽  
Printing Parameters

Fused Deposition Modeling (FDM), is one of the most popular and widely used Additive Manufacturing filament based technology employing materials such as Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Thermoplastic Polyurethane (TPU) and Polylactic Acid (PLA). In this technique, the part is built up layer-by-layer, affecting, both the resolution along the z-axis, and the mechanical properties dependent on the mesostructure, controlled by a large amount of production parameters such as layer thickness, raster orientation, number of contour and air gap. When dealing with functional and structural printed parts, a deep understanding of these tunable building parameters and their influence on the mechanical properties is of the utmost importance and over the years many experimental studies have been carried to investigate this need. This study is intended to explore specimens realized through FDM technique with different combinations of printing parameters to analyse their effect on the mechanical properties of ABS Plus p430. To this aim, tensile and compression specimens, had been designed and tested. Sixteen different types of tensile specimen had been realized by varying four different parameters, namely, layer thickness, part interior style, infill orientation and number of contours. Whereas, the number of compression specimens had been limited to four considering the variation of two parameters: layer thickness and part interior style. Three samples for each specimen had been produced in ABS Plus p430 using a Stratasys Fortus 250mc FDM printer and tested with a universal testing machine through tension and compression tests to analyse the correlation between printing parameters and material properties. Test results had led to important conclusions on the consistency and homogeneity of the mechanical properties and on the variation of the material’s performances in accordance with the different combinations of production parameters.

scholarly journals EXPERIENCE OF SEALING WEAK WATER-SATURATED LOESS SOILS WITH VERTICAL SAND DRAINS IN SEISMIC REGIONS

2019 ◽  
Vol 10 (2) ◽  
pp. 26-35
Author(s):  
R. A Mangushev ◽  
R. A Usmanov
Keyword(s):  
Experimental Studies ◽  
Layer By Layer ◽  
Loess Soils ◽  
Central Asian ◽  
Parameter Field ◽  
The Republic ◽  
Seismic Impact ◽  
Water Saturated

The article presents the results of studies relating to compaction of weak water-saturated forest soils and vertical sandy drains under static and seismic effects in the conditions of the Central Asian region. Considering the absence of any experimental and theoretical studies of the application of this parameter, field (in-situ) experimental studies were carried out to identify the possibilities and effectiveness of its use in conditions of weak water-rich loess soils of the Republic of Tajikistan. The article discusses changes in the basic physical and mechanical characteristics of soils and experimental structures. At the experimental site, three plots with a size of 10·10 m were prepared, where the plot was loaded without the installation of vertical sand drains; 3·3 m to a depth of 6.0 m. Static loading of experimental plots by a derivative by layer-by-layer dumping of ground material with measurement of total and layer-by-layer deformations of the packed thickness. Imitation of seismic impact with an intensity of 8 points was carried out using short-delayed explosions of explosive charges. Studies have shown the effectiveness of the use of vertical sandy drains for compaction of weak water-saturated loess soils. Recommendations are given on the use of explosion energy to improve the quality of soil compaction.

scholarly journals Effect of Shape of Armoring Fibers on Strength of Composite Materials

2021 ◽  
Vol 12 (2) ◽  
pp. 2703-2708
Author(s):  
Y.A.Vahterova, Et. al.
Keyword(s):  
Composite Materials ◽  
Deformation Rate ◽  
Experimental Studies ◽  
Layered Material ◽  
Carbon Plastic ◽  
Test Results ◽  
Static Characteristics ◽  
Calculation Results ◽  
Margin Of Safety ◽  
Design Calculations

In this work, experimental studies of the effect of fiber curvature on the strength and ultimate deformations of epoxy carbon plastic samples under loading are carried out. On the basis of the experimental studies carried out, the static characteristics of the composite layered material, which are promising for use in the structures under consideration, have been determined. Based on the test results, it was demonstrated that in the design calculations for the products under consideration, it is possible to use static characteristics, since an increase in the deformation rate of the material leads to an increase in strength and, therefore, the calculation results will provide an additional margin of safety.

scholarly journals Nacre Shell Inspired Self Assembly of Graphene Oxide-Lipid Nanocomposites

2021 ◽  
Author(s):  
Greeshma Chathamkandath Raghuvaran ◽  
Keyword(s):  
Graphene Oxide ◽  
Self Assembly ◽  
Lipid Membranes ◽  
Experimental Studies ◽  
Layer By Layer ◽  
Fabrication Method ◽  
X Ray Diffraction ◽  
Free Standing ◽  
Sem Images ◽  
Inherent Strength

Nanoscale graphene oxide-lipid composites have shown wide applications in the field of biosensing and nanosafety. Macroscopic free-standing membranes of this combination potentially offer excellent mechanical properties which can be attributed to the inherent strength of graphene oxide(GO). Previous experimental studies have mostly dealt with monolayer or bilayer interactions of lipids with graphene and graphene oxide surfaces. In our study, we report for the first time, a simple and scalable fabrication method where Small Unilamellar Vesicles (SUVs) of 1,2-dioleoyl-sn-glycero-3-phosphocholine(DOPC) combine with graphene oxide to produce stable nanocomposites via self-assembly. Scanning Electron Microscopy (SEM) images of the composite revealed layer-by-layer structures, reconfirmed by X-Ray Diffraction(XRD) results which show a proportional increase in the interlayer separation with an increasing ratio of lipid in graphene oxide. The nanocomposite thus fabricated mimics naturally occurring nacre shell structures where graphene oxide substitutes the strong aragonite layers, and the intermediate lipid layers provide the necessary elasticity pertaining to protein chitin in nacre. The addition of lipids to graphene-based nanocomposites also serves as a biodegradable alternative to using polymers as a popular reinforcement agent. The ease of fabrication method reported facilitates the production of stable GO-Lipid membranes in variable scales and geometries.

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