Thermal Diffusivity of Heterogeneous Materials

Kerrisk, J.F.

doi:10.1063/1.1659581

Cited by 48 publications

(17 citation statements)

References 4 publications

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“…is the thermal conductivity of the specimen having a porosity p. ρ 0 and c 0 are the density and specific heat capacity, respectively, of the specimen with zero porosity [22]. If the thermal conductivity of the porous material is modified by the same ratio as that of the ratio between the actual density and maximum density, the thermal conductivity is given by the Leob equation [23], K c (p) = K 0 (1 − p).…”

Section: Resultsmentioning

confidence: 99%

Photoacoustic Thermal Characterization of Porous Rare-Earth Phosphate Ceramics

et al. 2007

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The laser induced non-destructive photoacoustic technique has been employed to measure the thermal diffusivity of lanthanum phosphate ceramics prepared by the sol-gel route. The thermal diffusivity value was evaluated by knowing the transition frequency between the thermally thin to thermally thick region from the log-log plot of photoacoustic amplitude versus chopping frequency. Analysis of the data was carried out on the basis of the one-dimensional model of Rosencwaig and Gersho. The present investigation reveals that the sintering temperature has great influence on the propagation of heat carriers and hence on the thermal diffusivity value. The results were interpreted in terms of variations in porosity with sintering temperature as well as with changes in grain size.

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Section: Resultsmentioning

confidence: 99%

Photoacoustic Thermal Characterization of Porous Rare-Earth Phosphate Ceramics

et al. 2007

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“…This assumption may be acceptable if the scale of the microstructure is far smaller than the size of the sample, and this is obviously true for sufficiently thick samples (Kerrisk 1971(Kerrisk , 1972Taylor 1976b, 1978).…”

Section: Compositesmentioning

confidence: 96%

Flash method of measuring the thermal diffusivity. A review

Vozár¹,

Hohenauer²

2003

High Temp.-High Press.

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It is more than forty years since Parker et al (1961, working for the US Navy Radiological Defense Laboratory, released their original paper introducing the flash technique. Since then this photothermal experimental method has been extended worldwide and it has become the most popular method for the measurement of the thermal diffusivity of solids. The simplicity and the efficiency of the measurement, the accuracy and the reliability of results, and possibilities of application under a wide range of experimental conditions and materials are the main advantages of the flash method. The fact that the flash method has received standard status in many countries acknowledges its universality.We present an up-to-date summary of the theory and application of the flash method. We discuss the ideal adiabatic model and non-ideal models that account for the influence of the main disturbing phenomenaö heat losses from the sample, finite heat pulse durations, and nonuniform heating effects. The paper focuses on the survey of data-reduction methodsö algorithms for calculation of thermal diffusivity from the experimental data. It provides also references to several original papers with descriptions of the experimental apparatus. Attention is given to applications of the flash method for the measurement of advanced materialsösemitransparent media, materials with significant dependence of their thermophysical properties on temperature, anisotropic materials, layered structures, thin films, and composites. The paper contains a short note about various experimental methods having their origin in the flash method.

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“…Provided that the material is made of a large number of particles randomly distributed in a homogeneous matrix, a rough estimate of the effective thermal conductivity is also possible by using the following relationship [6]: k=k ki(1+2(P)+2km(1(P) (2) m ki(1(P)+km(2+() Eq. (2) has been evaluated for spherical particles, but can be applied to porous materials, attributing null conductivity to the porous alveoli [7]. Paying more caution, it can even be applied to short-length-fiber composites, but not to long-length-fiber ones.…”

Section: Approaches To Modeling Of Composite Structuresmentioning

confidence: 96%

“…The criterion is also proposed that the scale of heterogeneity of the material, i.e. the dimension of the unit-cell, must be much smaller than the minimum thermal wavelength associated to the thermal diffusion problem, for extending to transient conditions the validity of the relationships for the steady-state estimate of the effective conductivity tensor [6,7,10]. In TNDE inspection of long-length-fiber composites, this criterion is usually satisfied for heat flow transverse to the fiber direction [11], whereas for longitudinal properties the volume fraction of fiber must also be as large as possible and the contact thermal resistance between fiber and matrix very low [11].…”

Section: Approaches To Modeling Of Composite Structuresmentioning

confidence: 99%

<title>Modeling of thermal nondestructive evaluation techniques for composite materials</title>

et al. 2000

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The inspection of composite structures by thermal non-destructive evaluation (TNDE) techniques based on Infrared Thermography is relatively common in the aerospace industry. However, state-of-the-art is far to be reached and there is still place for substantial improvement, in terms of development of the inspection procedures, optimization of the experimental set-up and assessment of the inversion algorithms. This requires the availability of large amounts of reference data, which can be provided in a cost-effective way by mathematically modeling the thermal behavior of the inspected structures. The numerical simulation of procedures for thermographic inspection is investigated in this work. The analysis is focused on the strategies that can be implemented to model the heat conduction processes in composite structures typical of TNDE procedures by means of commercial software packages for coupled mechanical-thermal analyses. The results of a pilot application of a commercial software packages to a real case are finally presented.

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Thermal Diffusivity of Heterogeneous Materials

Cited by 48 publications

References 4 publications

Photoacoustic Thermal Characterization of Porous Rare-Earth Phosphate Ceramics

Photoacoustic Thermal Characterization of Porous Rare-Earth Phosphate Ceramics

Flash method of measuring the thermal diffusivity. A review

<title>Modeling of thermal nondestructive evaluation techniques for composite materials</title>

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