scholarly journals Mechanical and Thermal Behavior of Fibrous Carbon Materials

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1796
Author(s):  
Blagoj Karakashov ◽  
M’Barek Taghite ◽  
Richard Kouitat ◽  
Vanessa Fierro ◽  
Alain Celzard
Keyword(s):  
Thermal Conductivity ◽  
Elastic Modulus ◽  
Fiber Orientation ◽  
Carbon Materials ◽  
Mechanical Test ◽  
Measurement Techniques ◽  
Conductivity Measurement ◽  
High Porosity ◽  
Fibrous Materials ◽  
Fibrous Carbon

The ability of various commercial fibrous carbon materials to withstand stress and conduct heat has been evaluated through experimental and analytical studies. The combined effects of different micro/macro-structural characteristics were discussed and compared. Large differences in mechanical behavior were observed between the different groups or subgroups of fibrous materials, due to the different types of fibers and the mechanical and/or chemical bonds between them. The application of the Mooney–Rivlin model made it possible to determine the elastic modulus of soft felts, with a few exceptions, which were studied in-depth. The possible use of two different mechanical test methods allowed a comparison of the results in terms of elastic modulus obtained under different deformation regimes. The effective thermal conductivity of the same fibrous materials was also studied and found to be much lower than that of a single carbon fiber due to the high porosity, and varied with the bulk density and the fiber organization involving more or less thermal contact resistances. The thermal conductivity of most materials is highly anisotropic, with higher values in the direction of preferential fiber orientation. Finally, the combination of compression and transient thermal conductivity measurement techniques allowed the heat conduction properties of the commercial fibrous carbons to be investigated experimentally when compressed. It was observed that thermal conductivity is strongly affected under compression, especially perpendicular to the main fiber orientation.

scholarly journals Solid Layer Thermal-Conductivity Measurement Techniques

1994 ◽  
Vol 47 (3) ◽  
pp. 101-112 ◽  
Author(s):  
K. E. Goodson ◽  
M. I. Flik
Keyword(s):  
Thermal Conductivity ◽  
Infrared Detectors ◽  
Laser Light ◽  
Measurement Techniques ◽  
Conductivity Measurement ◽  
Thin Layers ◽  
Optical Coatings ◽  
Solid Layer ◽  
Laser Systems ◽  
Very High

The thermal conductivities of solid layers of thicknesses from 0.01 to 100 μm affect the performance and reliability of electronic circuits, laser systems, and microfabricated sensors. This work reviews techniques that measure the effective thermal conductivity along and normal to these layers. Recent measurements using microfabricated experimental structures show the importance of measuring the conductivities of layers that closely resemble those in the application. Several promising non-contact techniques use laser light for heating and infrared detectors for temperature measurements. For transparent layers these methods require optical coatings whose impact on the measurements has not been determined. There is a need for uncertainty analysis in many cases, particularly for those techniques which apply to very thin layers or to layers with very high conductivities.

Not Enough Precision to Accurately Measure the Effect of CNT Functionalization on the Thermal Conductivity of PDMS/CNT Composite Under Strain Using Stepped-Bar Apparatus

2015 ◽  
Author(s):  
Matthew I. Ralphs ◽  
Nicholas Roberts
Keyword(s):  
Thermal Conductivity ◽  
Polymer Matrix ◽  
Measurement Techniques ◽  
Conductivity Measurement ◽  
Hydroxyl Group ◽  
Mechanical And Thermal Properties ◽  
Conductive Composites ◽  
Aerospace Applications ◽  
The Matrix ◽  
Thermally Conductive

Carbon nanotubes (CNTs) exhibit extraordinary mechanical and thermal properties and as such have become the subject of large research interest. Furthermore, CNTs in a polymer matrix have been shown to significantly enhance the thermal conductivity of the polymer/CNT composite in some cases. A few areas of application for this work are thermal interface materials, thermally conductive composites used in aerospace applications, and polymer heat exchangers. In each of these applications the purpose of the polymer or epoxy is to take advantage of the mechanical properties or chemical inertness. The current issue with their adoption is still the poor thermal conductivity. One approach to overcoming this issue is to embed thermally conductive materials into the host material in low concentrations to enhance the effective thermal conductivity. There has been a significant amount of work in this area, but we are far from an understanding that allows us to design a nanocomposite that gives the desired thermal conductivity (specifically in the high thermal conductivity range). This work explores the role that chemical modification (functionalization) of the CNT can play in tailoring thermal transport properties of the composite under strain. It is expected that the functionalization process would have some effect on conduction between the CNT and the polymer matrix and therefore either increase or decrease the ability of the composite to transport thermal energy. This paper focuses on three different functionalizations of CNT and explores the thermal conductivity of a polymer/CNT composite that uses polydimethylsiloxane (PDMS) as the matrix. The three functionalizations of CNTs considered are that of unfunctionalized, functionalized with a carboxyl group (-COOH), and functionalized with a hydroxyl group (-OH). The CNTs used in this study are strictly multi-walled carbon nanobutes (MWCNTs) purified to 95%. The effect of these three functionalizations on the overall thermal conductivity of the composite is evaluated through experimental methods with a stepped bar apparatus at various levels of strain on the composite sample. Results show that, while functionalization of the CNT may affect the CNT/PDMS bond, the stepped bar apparatus does not provide enough precision on the level of strain placed on the sample for a comparison across functionalizations. Future work will try to elucidate both the effect of strain and functionalization using multiple thermal conductivity measurement techniques.

scholarly journals Development of Experimental Setup for Measuring Thermal Conductivity Characteristics of Soil

2018 ◽  
Vol 37 (4) ◽  
pp. 559-568 ◽  
Author(s):  
Gul Muhammad ◽  
Amanullah Marri ◽  
Abdul Majeed Shar
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Stresses ◽  
Measurement Techniques ◽  
Conductivity Measurement ◽  
Theoretical Background ◽  
Experimental Setup ◽  
Engineering Structures ◽  
Steady State Heat ◽  
Set Up

Thermal conductivity displays a key role in design of engineering structures where, thermal stresses resulting from heat and temperatures are of concern. Significant efforts were made to measure the thermal conductivity of different materials. For thermal conductivity characterization of soil samples it is essential to have very flexible set-up. Hence, this paper provides details about indigenously developed experimental setup for thermal conductivity measurement. The design of this newly developed setup is based on the basic principle of steady state heat flow. This experimental setup is designed in order to measure the thermal conductivity of various materials such as soils, rocks, concrete and any type of unbonded and bonded materials. In this paper, initially the theoretical background of the measurement techniques and the principle of heat flow are described, followed by design description and working procedure. The design has been kept very simple, adjustable for varying type and size of specimens and easy to operate with excellent level of accuracy as evident from system calibration. The accuracy and precision of the newly developed setup was verified by testing reference materials of known thermal conductivity and in the test results a high correlation coefficient (R^2 = 0.999) between experimental data and fitting curve was achieved.

scholarly journals Development of Experimental Setup for Measuring Thermal Conductivity Characteristics of Soil

2018 ◽  
Vol 37 (4) ◽  
pp. 559-568
Author(s):  
Gul Muhammad ◽  
Amanullah Marri ◽  
Abdul Majeed Shar
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
Thermal Stresses ◽  
Measurement Techniques ◽  
Conductivity Measurement ◽  
Theoretical Background ◽  
Experimental Setup ◽  
Engineering Structures ◽  
Steady State Heat ◽  
Set Up

Thermal conductivity displays a key role in design of engineering structures where, thermal stresses resulting from heat and temperatures are of concern. Significant efforts were made to measure the thermal conductivity of different materials. For thermal conductivity characterization of soil samples it is essential to have very flexible set-up. Hence, this paper provides details about indigenously developed experimental setup for thermal conductivity measurement. The design of this newly developed setup is based on the basic principle of steady state heat flow. This experimental setup is designed in order to measure the thermal conductivity of various materials such as soils, rocks, concrete and any type of unbonded and bonded materials. In this paper, initially the theoretical background of the measurement techniques and the principle of heat flow are described, followed by design description and working procedure. The design has been kept very simple, adjustable for varying type and size of specimens and easy to operate with excellent level of accuracy as evident from system calibration. The accuracy and precision of the newly developed setup was verified by testing reference materials of known thermal conductivity and in the test results a high correlation coefficient (R2 = 0.999) between experimental data and fitting curve was achieved.

scholarly journals The Dependence of Aftereffects and Contact of Rough Surfaces Composite – Metal from Orientation Factors of Dispersed Phase of Polymer Matrix

2016 ◽  
Vol 17 (2) ◽  
pp. 294-305
Author(s):  
H.O. Sirenko ◽  
L.M. Soltys
Keyword(s):  
Fiber Orientation ◽  
Friction Surface ◽  
Carbon Materials ◽  
Friction Pair ◽  
Surface Friction ◽  
Sliding Direction ◽  
Orientation Effects ◽  
Carbon Plastics ◽  
Fibrous Carbon ◽  
Surface Changes

Results of researches of influence orientation effects on the friction properties of carbon-plastics and wear mechanism of unidirectional carbon-plastics have been brought in a work. The optimal structure of carbon-plastics and fiber orientation layers in it relative to the surface friction and sliding direction have been provided. The influence of schemes reinforcing by fibrous carbon materials of polymer composites and schemes contacting of samples composites with the surface of metal counterface on the intensity of wear of friction pair and on the changing of microroughness parameters of metal surface have been researched. It has been shown that the topography of metal counterface surface changes in friction carbon plastics with oriented fibers, but the allocation of heights and curvatures of microroughness peaks of friction surface far removed from the Gaussian allocation and close to Rayleigh allocation.

Comparison of Available Silicone Rubber Coatings for High Voltage Applications

2008 ◽  
Vol 9 (1) ◽  
Author(s):  
Majid Sanaye-Pasand ◽  
Ali Naderian Jahromi ◽  
Ayman H El-Hag ◽  
Shesha H Jayaram
Keyword(s):  
Thermal Conductivity ◽  
High Voltage ◽  
Transmission Lines ◽  
Silicone Rubber ◽  
Mechanical Test ◽  
Conductivity Measurement ◽  
Inclined Plane ◽  
Rubber Coatings ◽  
Salt Fog ◽  
Inclined Plane Test

This paper presents the results of an investigation on evaluating room-temperature-vulcanized (RTV) silicone rubber coatings for high-voltage insulators of substations and overhead transmission lines. It is based on tests conducted for three different available RTVs that are currently used by utilities. The study compared three commercial coatings: RTV-A and RTV-B filled with ATH (aluminum tri-hydrate) as the primary filler, and RTV-C filled with silica. The relative comparison between them is based on their electrical and chemical characteristics. The evaluation employed standard and research-based evaluation methods, including the salt fog test, the inclined plane test, thermo-gravimetric analyses (TGA), thermal conductivity measurement, soaking in water, the mechanical test, and SEM photographs. Results of the inclined plane test showed that the silica-filled coating is not resistive against tracking and erosion compared with ATH-filled coatings. It was observed that filler size is one of the main reasons for better performance of RTV-A compared with RTV-B, whereas both have ATH as the primary filler. The higher thermal conductivity of RTV-A resulted in a very good performance in the salt fog test and the IPT.

Analysis of significant measures for thermal conductivity

2020 ◽  
pp. 35-42
Author(s):  
Yuri P. Zarichnyak ◽  
Vyacheslav P. Khodunkov
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Surface Heat Flux ◽  
Heat Flux Density ◽  
Measurement Method ◽  
Conductivity Measurement ◽  
Surface Heat ◽  
Measuring Instrument ◽  
New Class ◽  
Achievable Accuracy

The analysis of a new class of measuring instrument for heat quantities based on the use of multi-valued measures of heat conductivity of solids. For example, measuring thermal conductivity of solids shown the fallacy of the proposed approach and the illegality of the use of the principle of ambiguity to intensive thermal quantities. As a proof of the error of the approach, the relations for the thermal conductivities of the component elements of a heat pump that implements a multi-valued measure of thermal conductivity are given, and the limiting cases are considered. In two ways, it is established that the thermal conductivity of the specified measure does not depend on the value of the supplied heat flow. It is shown that the declared accuracy of the thermal conductivity measurement method does not correspond to the actual achievable accuracy values and the standard for the unit of surface heat flux density GET 172-2016. The estimation of the currently achievable accuracy of measuring the thermal conductivity of solids is given. The directions of further research and possible solutions to the problem are given.

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