2-Scale Hierarchical Multiscale Modeling of Piezoresistive and Damage Response in Polymer Nanocomposite Bonded Explosive

2016 ◽  
Author(s):  
Krishna K. Talamadupula ◽  
Adarsh K. Chaurasia ◽  
Gary D. Seidel
Keyword(s):  
Polymer Nanocomposite ◽  
Grain Structure ◽  
Polymer Medium ◽  
Piezoresistive Effect ◽  
Weight Percentage ◽  
Hierarchical Framework ◽  
Damage Response ◽  
Work Done ◽  
Hierarchical Multiscale ◽  
Cohesive Zones

This paper builds on previous work done [1, 2] to explore the effective piezoresistive response of polymer bonded explosive (PBX) materials where the polymer medium is reinforced with carbon nanotubes (CNTs). In the present work, the nanocomposite binder is modeled explicitly as a piezoresistive material whose properties are determined from the nanoscale through a micromechanics based 2-scale hierarchical model connecting the nanoscale to the microscale grain structure. Electromechanical cohesive zones are used to model the interface between the grains and nanocomposite binder in order to characterize interface separation and the resulting piezoresistive effect. The overall microscale piezoresistive effect is measured by using the volume averaged properties of the microscale RVE. The hierarchical framework developed here is used to explore key features of the NCBX microstructure such as the effect of grain conductivity, weight percentage of CNTs used and nanocomposite gage factor.

2-Scale Hierarchical Multiscale Modeling of Piezoresistive Response in Polymer Nanocomposite Bonded Explosives

2015 ◽  
Author(s):  
Krishna K. Talamadupula ◽  
Adarsh K. Chaurasia ◽  
Gary D. Seidel
Keyword(s):  
Multiscale Modeling ◽  
Polymer Nanocomposite ◽  
Grain Structure ◽  
Current Work ◽  
Interfacial Damage ◽  
Polymer Medium ◽  
Hierarchical Framework ◽  
Key Features ◽  
Hierarchical Multiscale ◽  
Cohesive Zones

The current work aims to explore the effective piezoresistive response of polymer bonded explosive (PBX) materials where the polymer medium is reinforced with carbon nanotubes (CNTs). The effective piezoresistive response of these nanocomposite bound polymer explosives (NCBX) is evaluated using micromechanics based 2-scale hierarchical model connecting the CNT-polymer nanocomposite scale (nanoscale) to the explosive grain structure scale (microscale). The binding nanocomposite medium is modeled as electromechanical cohesive zones between adjacent explosive grains which are representative of effective electromechanical response of CNT-polymer nanocomposites. The hierarchical framework developed here is used to explore key features of the NCBX microstructure, e.g. ratio of grain to nanocomposite stiffness, ratio of grain to nanocomposite conductivities etc., and related to the NCBX effective piezoresistive response. The results obtained from the current work show dependence of effective NCBX piezoresistive properties on each of these microstructural features with and without interfacial damage between the explosive grains.

Comparative Study on Partial Discharge Characteristic in Polymer-Nanocomposite as Electrical Insulating Material

2013 ◽  
Vol 284-287 ◽  
pp. 62-66
Author(s):  
Wan Akmal Izzati ◽  
Mohd Shafanizam ◽  
Yanuar Z. Arief ◽  
Mohamad Zul Hilmey Makmud ◽  
Zuraimy Adzis ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Polymer Nanocomposites ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Partial Discharge ◽  
Specific Area ◽  
Polymer Nanocomposite ◽  
Insulating Material ◽  
Weight Percentage ◽  
Experimental Works

Polymer nanocomposites have been attracting attention among researchers as electrical insulating application from energy storage to power delivery. However, partial discharge has always been a predecessor to major faults and problems in this field. In addition, there are a lot more to explore as the characteristic of partial discharge in nanocomposites is not clearly understood as well as the electrical properties of the nanocomposites. By adding a few amount of weight percentage (wt%) of the nano fillers, the physical, mechanical and electrical properties of polymers can be greatly enhanced. This is due to its amazing characteristic of having large specific area as a consequential from its nano sized particle that could enhance the electrical properties of the insulator. For instance, nano fillers in nanocomposites such as silica (SiO2), alumina (Al2O3) and titania (TiO2), play big role in providing good approach to increase dielectric breakdown strength and partial discharge resistance of nanocomposites. Such polymer nanocomposites will be reviewed thoroughly in this paper based on previous experimental works and studies. This paper provides reviews from related publications from year 1997 to 2011 including the results of experimental works which have been conducted by the authors with main focus on partial discharge characteristics in polymer nanocomposites, which demonstrates that research and utilization of polymer nanocomposites has well developed from past decades and will possess a high demand in future as electrical insulating material.

Exploring the Structural and Dielectric Properties of Polymer Films Incorporating Carbon-Based Nanomaterials

2021 ◽  
Vol 20 (02) ◽  
pp. 2150019
Author(s):  
A. Deepak ◽  
Pheba Cherian ◽  
D. F. L. Jenkins
Keyword(s):  
Vinylidene Fluoride ◽  
Tunneling Current ◽  
Polymer Nanocomposite ◽  
Wide Frequency Range ◽  
Nanocomposite Films ◽  
Host Matrix ◽  
Weight Percentage ◽  
Poly Vinylidene Fluoride ◽  
Electrical Permittivity ◽  
Carbon Based Nanomaterials

This work explores the electrical, dielectric and physical characteristics of multi-walled carbon nanotube (MWCNT) and graphene reinforced Poly vinylidene fluoride (PVDF) polymer nanocomposite films, over a wide frequency range, ranging from 1 Hz to 1 MHz. Films are prepared with different weight percentage of MWCNTs or graphene powder within a PVDF host matrix and its intrinsic properties are compared with pure PVDF films. As the weight percentage increases, the material properties such as conductivity (electrical), permittivity (dielectric) and capacitance (dielectric) will change. PVDF is a dielectric and the fillers are conductors, and this gives rise to the phenomenon of percolation, as the weight percentage of conducting fillers increases. This paper explores film’s properties for different weight percentage of MWCNTs and graphene fillers. Tunneling current of graphene–PVDF films are also compared with MWCNT–PVDF films.

scholarly journals Nanocarbon/Poly(Lactic) Acid for 3D Printing: Effect of Fillers Content on Electromagnetic and Thermal Properties

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2369 ◽  
Author(s):  
Giovanni Spinelli ◽  
Patrizia Lamberti ◽  
Vincenzo Tucci ◽  
Rumiana Kotsilkova ◽  
Evgeni Ivanov ◽  
...  
Keyword(s):  
Thermal Properties ◽  
3D Printing ◽  
Electromagnetic Interference ◽  
Thermal Characteristics ◽  
Polymer Nanocomposite ◽  
Thermal Characterization ◽  
Thermal Dissipation ◽  
Poly Lactic Acid ◽  
Weight Percentage ◽  
Multi Walled Carbon Nanotubes

Electromagnetic and thermal properties of a non-conventional polymer nanocomposite based on thermoplastic Polylactic acid (PLA, Ingeo™) filled, in different weight percentage, with multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs), as well as a mixture of both fillers (MWCNTs/GNPs), are analyzed. The combination of notable electrical, thermal, and electromagnetic (EM) properties of the carbon fillers, in concentrations above the percolation threshold, together with the good processability of the PLA matrix gives rise to innovative filaments for 3D printing. In particular, the shielding efficiency (SE) in the frequency range 26–37 GHz of samples increases from 0.20 dB of unfilled PLA up to 13.4 dB for composites containing MWCNTs and GNPs, corresponding to 4% and 95% of SE, respectively. The thermal conductivity of the PLA loaded with 12 wt % of GNPs is 263% higher than that of the unfilled polymer, whereas an improvement of about 99% and 190% is detected for the PLA matrix loaded with MWCNTs and both fillers, respectively. The EM and thermal characterization is combined with a morphological investigation allowing us to correlate the dispersion states of the fillers within the polymer matrix with the observed EM and thermal properties. The EM and thermal characteristics exhibited by the nanocomposites make them suitable for packaging applications of electronic devices with electromagnetic interference (EMI) shielding and thermal dissipation features.

scholarly journals Influence of Organo-Montmorillonite on Electrical Tree Parameters in Epoxy Resin Under Ac Ramp Voltage

2013 ◽  
Vol 64 (4) ◽  
Author(s):  
Mohd Hafiez Izzwan Saad ◽  
Mohd Hafizi Ahmad ◽  
Yanuar Z. Arief ◽  
Hussein Ahmad ◽  
Mohamed Afendi Mohamed Piah
Keyword(s):  
Epoxy Resin ◽  
Breakdown Voltage ◽  
Polymer Nanocomposite ◽  
Weight Percentage ◽  
Electrical Tree ◽  
Base Polymer ◽  
Ramp Voltage ◽  
Comparative Results ◽  
Inception Voltage ◽  
Electrical Treeing

This paper discusses the effects of nanofiller on electrical treeing growth in polymer nanocomposites. The polymer nanocomposite consists of epoxy resin as the base polymer and organo-montmorillonite as the nanofiller. The influence of this nanofiller on the electrical treeing breakdown resistance was investigated experimentally. The quantity of organo-montmorillonite were added in epoxy resin by ultrasonication method based on weight percentage (wt%). The weight percentages used in this experiment were 0 wt% and 1 wt%, respectively. All the samples were produced in the form of leaf-like specimens which were categorized into two parts: unfilled sample (0 wt%) and filled sample (1 wt%). Point-to-plane samples were subjected to 0.5 kVrms/s HVAC ramp voltage. The data of tree inception voltage and tree breakdown voltage were collected and comparative results were made and presented. The morphological analysis of epoxy nanocomposites were investigated using field emission scanning electron microscopy (FESEM). Electrical tree parameters analysis has shown that the existence of organo-montmorillonite in epoxy resin could exhibit significant improvement of tree characteristics of epoxy resin nanocomposites as the nanofiller contributed to the increase of tree inception voltage and tree breakdown voltage.

scholarly journals Nano-Level Damage Characterization of Graphene/Polymer Cohesive Interface under Tensile Separation

Polymers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1435 ◽  
Author(s):  
S. S. R. Koloor ◽  
S. M. Rahimian-Koloor ◽  
A. Karimzadeh ◽  
M. Hamdi ◽  
Michal Petrů ◽  
...  
Keyword(s):  
Cohesive Zone ◽  
Cohesive Zone Model ◽  
Polymer Nanocomposite ◽  
Zone Model ◽  
Polymer Interfaces ◽  
Damage Behavior ◽  
Epoxy Nanocomposite ◽  
Cohesive Interface ◽  
Damage Response

The mechanical behavior of graphene/polymer interfaces in the graphene-reinforced epoxy nanocomposite is one of the factors that dictates the deformation and damage response of the nanocomposites. In this study, hybrid molecular dynamic (MD) and finite element (FE) simulations of a graphene/polymer nanocomposite are developed to characterize the elastic-damage behavior of graphene/polymer interfaces under a tensile separation condition. The MD results show that the graphene/epoxy interface behaves in the form of elastic-softening exponential regressive law. The FE results verify the adequacy of the cohesive zone model in accurate prediction of the interface damage behavior. The graphene/epoxy cohesive interface is characterized by normal stiffness, tensile strength, and fracture energy of 5 × 10−8 (aPa·nm−1), 9.75 × 10−10 (nm), 2.1 × 10−10 (N·nm−1) respectively, that is followed by an exponential regressive law with the exponent, α = 7.74. It is shown that the commonly assumed bilinear softening law of the cohesive interface could lead up to 55% error in the predicted separation of the interface.

The Nature of Delta Phase Precipitation in Inconel 718

1982 ◽  
Vol 40 ◽  
pp. 724-725
Author(s):  
L. S. Lin ◽  
C. C. Law
Keyword(s):  
Inconel 718 ◽  
Base Alloy ◽  
High Strength ◽  
Physical Metallurgy ◽  
Nickel Base Alloy ◽  
Phase Precipitation ◽  
Weight Percentage ◽  
Delta Phase ◽  
The Subject ◽  
Nickel Base

Inconel 718, a precipitation hardenable nickel-base alloy, is a versatile high strength, weldable wrought alloy that is used in the gas turbine industry for components operated at temperatures up to about 1300°F. The nominal chemical composition is 0.6A1-0.9Ti-19.OCr-18.0Fe-3Mo-5.2(Cb + Ta)- 0.1C with the balance Ni (in weight percentage). The physical metallurgy of IN 718 has been the subject of a number of investigations and it is now established that hardening is due, primarily, to the formation of metastable, disc-shaped γ" an ordered body-centered tetragonal structure (DO2 2 type superlattice).

SEM analysis of DC magnetron sputtered beryllium films

1988 ◽  
Vol 46 ◽  
pp. 960-961
Author(s):  
E. F. Lindsey ◽  
C. W. Price ◽  
E. L. Pierce ◽  
E. J. Hsieh
Keyword(s):  
Fine Structure ◽  
Electron Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Ion Beam ◽  
Secondary Electron Emission ◽  
Sem Analysis ◽  
Fused Silica ◽  
Grain Structure ◽  
Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

1995 ◽  
Vol 53 ◽  
pp. 524-525
Author(s):  
Z. Horita ◽  
D. J. Smith ◽  
M. Furukawa ◽  
M. Nemoto ◽  
R. Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Energy State ◽  
High Energy ◽  
Grain Structure ◽  
Boundary Structure ◽  
Solid Solution Alloy ◽  
Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

High-resolution scanning electron microscopy of thin-film magnetic media of magnetic recording disk

1992 ◽  
Vol 50 (2) ◽  
pp. 1334-1335
Author(s):  
K. Ogura ◽  
H. Nishioka ◽  
N. Ikeo ◽  
T. Kanazawa ◽  
J. Teshima
Keyword(s):  
Thin Film ◽  
Fine Structure ◽  
High Resolution ◽  
Magnetic Recording ◽  
High Performance ◽  
Magnetic Hysteresis ◽  
Grain Structure ◽  
Magnetic Media ◽  
Cross Sectional ◽  
Resolution Observation

Structural appraisal of thin film magnetic media is very important because their magnetic characters such as magnetic hysteresis and recording behaviors are drastically altered by the grain structure of the film. However, in general, the surface of thin film magnetic media of magnetic recording disk which is process completed is protected by several-nm thick sputtered carbon. Therefore, high-resolution observation of a cross-sectional plane of a disk is strongly required to see the fine structure of the thin film magnetic media. Additionally, observation of the top protection film is also very important in this field.Recently, several different process-completed magnetic disks were examined with a UHR-SEM, the JEOL JSM 890, which consisted of a field emission gun and a high-performance immerse lens. The disks were cut into approximately 10-mm squares, the bottom of these pieces were carved into more than half of the total thickness of the disks, and they were bent. There were many cracks on the bent disks. When these disks were observed with the UHR-SEM, it was very difficult to observe the fine structure of thin film magnetic media which appeared on the cracks, because of a very heavy contamination on the observing area.

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