Heat transport in epoxy and polyester carbonyl iron microcomposites: The effect of concentration and temperature

2017 ◽  
Vol 52 (10) ◽  
pp. 1331-1338
Author(s):  
NW Pech-May ◽  
C Vales-Pinzon ◽  
A Vega-Flick ◽  
A Oleaga ◽  
A Salazar ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Carbonyl Iron ◽  
Numerical Differentiation ◽  
Photopyroelectric Technique ◽  
Iron Particles ◽  
High Concentration ◽  
Polyester Resins ◽  
Wide Range ◽  
Study Heat Transfer

Temperature dependence of the thermal diffusivity in composites of epoxy and polyester resins, loaded with carbonyl iron particles, has been studied using the photopyroelectric technique. Increments of eight and 2.5 times the thermal conductivity of the polymers are obtained, as the volume concentration of microparticles is increased from 0% to 40% for epoxy and from 0% to 20% for polyester matrices, respectively. Additionally, the thermal diffusivity falls systematically as the temperature is increased from 270 to 400 K; the effect is more pronounced for high concentration of microparticles in epoxy composites. The glass transition of the composites is explored by implementing a numerical differentiation algorithm. In order to explain the consequences of the loading of the composites on the thermal conductivity, a modified Lewis-Nielsen model, which includes the presence of crowded regions in the samples, is used to study heat transfer in a wide range of particle concentrations.

Hot Disk: A Transient Plane Source Technique for Rapid Thermal Conductivity Measurement

2002 ◽  
Author(s):  
Yi He ◽  
Grace S. Ng
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Temperature Increase ◽  
Conductivity Measurement ◽  
Constant Current ◽  
Plane Source ◽  
Transient Plane Source ◽  
Wide Range ◽  
Hot Disk ◽  
Conductivity Range

Abstract Hot disk metrology represents a transient plane source measurement technique for characterizing thermal conductivity and thermal diffusivity of a wide range of materials. In this technique, the hot disk sensor serves as a heat source and a thermometer. During the measurement, the sensor is sandwiched between two halves of a sample and a constant current is supplied to the sensor. The temperature increase at the sensor surface is strongly dependent on the thermal transport properties of the surrounding material. By monitoring the temperature increase as a function of time, one can determine the thermal conductivity and thermal diffusivity of the surrounding material. The main advantages of the hot disk technique include: wide thermal conductivity range, from 0.005 W/m·K to 500 W/m·K; wide range of materials, from liquid to solid; easy sample preparation; non-destructive; and more importantly, high accuracy (within 2% or better). In this paper, the basic theory of the hot disk technique will be discussed based on first principles. This technique has been successfully used to characterize a variety of thermal interface materials (TIMs) used in electronic packaging. The experimental results are in good agreement with the results obtained by another method.

Thermal Characterization of IM7/8552-1 Carbon-Epoxy Composites

2014 ◽  
Author(s):  
Messiha T. Saad ◽  
Sandi G. Miller ◽  
Torrence Marunda
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Carbon Fiber ◽  
Specific Heat ◽  
High Performance ◽  
Critical Role ◽  
Flash Method ◽  
Handling Characteristics ◽  
Wide Range

Thermal properties of composite materials such as, thermal conductivity, diffusivity, and specific heat are very important in engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells. Thermal conductivity is the property that determines the working temperature levels of the material; it plays a critical role in the performance of materials in high temperature applications, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this paper is to develop a thermal properties data base for the carbon fiber-epoxy (IM7/8552-1) composite. The IM7 carbon fiber is a continuous, high performance, intermediate modulus, PAN based fiber. This fiber has been surface treated and can be sized to improve its interlaminar shear properties, handling characteristics, and structural properties. The 8552 is a high performance tough epoxy matrix for use in primary aerospace structures. It exhibits good impact resistance and damage tolerance for a wide range of applications. The IM7/8552-1 is an amine cured unidirectional prepreg. The manufacturer recommended cure cycle for this material was followed, which includes consolidation under vacuum and autoclave pressure. The composite has a service temperature up to 121°C (250°F). The thermal properties of IM7/8552-1 carbon-epoxy have been investigated using experimental methods. The flash method was used to measure the thermal diffusivity of the composite. This method is based on the American Society for Testing and Materials standard, ASTM E1461. In addition, the Differential Scanning Calorimeter was used in accordance with the ASTM E1269 standard to measure the specific heat. The measured thermal diffusivity, specific heat, and density data were used to compute the thermal conductivity of the IM7/8552-1 carbon-epoxy composite.

scholarly journals Thermal properties of cement mortar with different mix proportions

2020 ◽  
Vol 70 (339) ◽  
pp. 224 ◽  
Author(s):  
P. Shafigh ◽  
I. Asadi ◽  
A. R. Akhiani ◽  
N. B. Mahyuddin ◽  
M. Hashemi
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Cement Mortar ◽  
Construction Material ◽  
Physical And Mechanical Properties ◽  
Sem Images ◽  
Heating And Cooling ◽  
Wide Range

The energy required for the heating and cooling of buildings is strongly dependant on the thermal properties of the construction material. Cement mortar is a common construction material that is widely used in buildings. The main aim of this study is to assess the thermal properties of cement mortar in terms of its ther­mal conductivity, heat capacity and thermal diffusivity in a wide range of grades (cement: sand ratio between 1:2 and 1:8). As there is insufficient information to predict the thermal conductivity and diffusivity of a cement mortar from its physical and mechanical properties, the relationships between thermal conductivity and diffu­sivity and density, compressive strength, water absorption and porosity are also discussed. Our results indicate that, for a cement mortar with a 28-day compressive strength in the range of 6–60 MPa, thermal conductivity, specific heat and thermal diffusivity are in the range of 1.5–2.7 W/(m.K), 0.87–1.04 kJ/kg.K and 0.89–1.26 (x10-6 m2/s), respectively. The scanning electron microscope (SEM) images showed that pore size varied from 18 μm to 946 μm for samples with different cement-to-sand ratios. The porosity of cement mortar has a signifi­cant effect on its thermal and physical properties. For this reason, thermal conductivity and thermal diffusivity was greater in cement mortar samples with a higher density and compressive strength.

scholarly journals Development of UO2 thermal diffusivity measurement with laser techniques

2021 ◽  
Vol 253 ◽  
pp. 07005
Author(s):  
Thomas Doualle ◽  
Vincent Le Guillous ◽  
Vincent Klosek ◽  
Claire Onofri-Marroncle ◽  
Matthieu Reymond ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Measurement Techniques ◽  
Material Model ◽  
Laser Flash ◽  
Flash Method ◽  
Infrared Microscopy ◽  
Thermal Diffusivity Measurement ◽  
Diffusivity Measurement ◽  
Wide Range

The knowledge of the thermal conductivity of nuclear fuel and its evolution as a function of temperature and burn up is a major challenge in the context of the evaluation and understanding of irradiated fuel performances in current reactors. It is also the case for the development and qualification of fuel for future reactors. Indeed, numerical simulations of the fuel behaviour under various conditions require the accurate knowledge of thermal conductivity over a wide range of temperature (from ambient to melting point temperature) but also at the scale of few tens of micrometres to take into account the microstructural effects on the thermomechanical evolution of the fuel in normal or incidental irradiation conditions. Different methods, using laser matter interactions, can deduce the thermal conductivity from a thermal diffusivity measurement. In this paper, the potential of two techniques, which present spatial resolution from millimetre to few tens microns, are discussed in the context of the determination of the fuel thermal conductivity: laser flash method and infrared microscopy. Experiments on graphite, as material model, have been conducted and validate these two thermal diffusivity measurement techniques. We present a measurement example for both methods on graphite and then a first experiment carried out with the infrared microscopy technique on UO2.

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