Thermal Diffusivity in Situ Measurements of Carbon/Carbon Composite Reinforcements

  • Agnés Juc-Bouhali
  • Renée Pujola
  • Daniel Balageas


The diffusivity of directional reinforced composites (3-D C/C) was measured using the flash method. Problems related to the heat losses and the pulse duration were considered. The variation in the diffusivity determined at various moments during the heating confirms the numerical simulations: instead of being a nearly constant quantity as it is true for a homogeneous medium, the apparent diffusivity for these materials is a monotonic function that decreases with time and depends on the sample thickness.

An original method is used which changes nothing in the usual measurement techniques but permits to find the homogenized diffusivity for the whole composite, the in situ axial diffusivity of the parallel reinforcement with controlled heat flux, and the diffusivity of an equivalent matrix representing the actual matrix with the transverse reinforcements. This method, using an optical measurement of the mean temperature on the rear surface of the sample, is compared by numerical simulation with the method determining the diffusivity of the reinforcement from the temperature-time history by a point measurement on the reinforcement alone. Results of this comparison show that the intrinsic precision of the proposed method is better.

The reinforcement axial diffusivity of several 3-D C/C materials was found to vary from 2.6 x 10-4 to 3-1 x 10-4 m2 s-1, values three times greater than the diffusivities of the equivalent homogeneous materials, which can be determined on very thick samples or calculated from steady-state measurements of the thermal conductivity and specific heat.


Thermal Contact Resistance Armco Iron Transverse Reinforcement Actual Matrix Rear Face 
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  1. 1.
    D.L. Balageas and A.M. Luc, Nonstationary thermal behavior of directional reinforced composites. Limit of application of thermal property homogenization, AIAA Paper 83–1471 (1983)Google Scholar
  2. 2.
    W. Fritz, W. Huttner, K. Maier and R. Brandt, Thermophysical properties of carbon-fibre/carbon matrix composites at high temperatures, Rev. Int. Hts Temp. Refr. 16: 350 (1979).Google Scholar
  3. 3.
    R. Taylor and R. Procter, Measurement of thermal diffusivity of carbon fibre carbon composites from 300-3000 K,Univ. Manchester/UMIST(U.K.), Report AF0SR-TR-81-0638 (1981).Google Scholar
  4. 4.
    R.E. Taylor, H. Groot and R. Shoemaker, Thermophysical properties of fine weave C/C composites, AIAA 81–1103 (1981).Google Scholar
  5. 5.
    W.J. Parker, R.J. Jenkins, C.P. Butler and G. Abbott, Flash method of determining thermal diffusivity, heat capacity and thermal conductivity, J. Appl. Phys. 32: 9: 1679 (1961)CrossRefGoogle Scholar
  6. 6.
    A.M. Luc and D. Balageas, Comportement thermique des composites à renforcement orienté soumis à des flux impulsionnels, to be published in High-Temp. High Pressure (1984).Google Scholar
  7. 7.
    D.L. Balageas, Determination par méthode flash des propriétés thermiques des constituants dfun composite à renforcement orienté, idem.Google Scholar
  8. 8.
    D.L. Balageas, Nouvelle méthode d1 interprétation des thermogrammes pour la détermination de la diffusivité par méthode impulsionnelle, Rev. Phys. Appl. 17: 227 (1982).CrossRefGoogle Scholar
  9. 9.
    M. Assouline, Private communication.Google Scholar
  10. 10.
    R.E. Taylor and L.M. Clark III, Finite pulse time effects in flash diffusivity method, High Temp. High Pres. 6: 65 (1974)Google Scholar
  11. 11.
    N. Coulon, Private communication.Google Scholar
  12. 12.
    T. Azumi and Y. Takahashi, Novel finite pulse-width correction in flash thermal diffusivity measurement, Rev. Sc. Instr. 52: 9: 1411 (1981).CrossRefGoogle Scholar
  13. 13.
    C.Y. Ho, and R. Powell, Thermal conductivity of the elements: a comprehensive review, J. Phys. Chem. Ref. Data 3, suppl. 1(1974).CrossRefGoogle Scholar
  14. 14.
    A.M. Luc and D.L. Balageas, Le problème de la definition de la mesure de la diffusivité thermique des matériaux composites a renforcement, ONERA TP 1981–30 (1981).Google Scholar
  15. 15.
    H.J. Lee and R.E. Taylor, Thermophysical properties of carbon/graphite fibres and MOD-3 fibre reinforced graphite, Carbon 13 (1975).Google Scholar
  16. 16.
    M.L. Minges AFML-TR-74-96 (1975).Google Scholar
  17. 17.
    R.E. Taylor, Thermal diffusivity of composites, TPRL 253 (1981).Google Scholar

Copyright information

© Purdue Research Foundation 1985

Authors and Affiliations

  • Agnés Juc-Bouhali
    • 1
  • Renée Pujola
    • 1
  • Daniel Balageas
    • 1
  1. 1.Division de ThermophysiqueOffice National d’Etudes et de Recherches Aérospatiales (ONERA)Châtillon CédexFrance

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