1. Thermal diffusivity identification by periodic method
Thermique des matériaux composites monolithiques
Modélisation-Caractérisation-“ Round Robin Test ”
Thermal diffusivity identification by periodic method
Laetitia PEREZ
Laurent AUTRIQUE
Jean-Jacques SERRA
Groupe des Hauts Flux
1. CEP research institute
2. Method and experimental device
3. Observations and signal processing
4. Identification results
5. Outlook remarks

2. CEP research institute
DGA
DET
CEP
LOT
GHF
equipment design, optimisation, protection
communications, security
human protection again aggressions
Odeillo

3. Experimentation - Modelisation - Characterisation
Groupe des Hauts Flux
Experimentation - Modelisation - Characterisation
Materials Test
Thermal effect of nuclear weapon
Damage evaluation
Thermal behavior under high flux
Burn occured by high radiant flux

4. Experimentation - Modelisation - Characterisation
Groupe des Hauts Flux
Experimentation - Modelisation - Characterisation
Properties characterisation
Optical properties determination
Thermal properties determination

5. Method and experimental device
Periodic input
State system observation
Modulus
Phase
frequency (f )
phase lag ()
Frequency (f )
Mathematical model :
complex temperature and inverse Fourrier transform
semi analytical solution : Matlab® simulation of the direct problem
Sensitivity analysis :
output signal modulus : nuisance parameters
output signal phase lag : depends on thermal diffusivity

6. Method and experimental device
IR camera
Sample
Köhler assembly
Process control
Measurements
Temperature spatial distribution
Signal processing : modulus and phase lag x y z

7. Observations and signal processing
Thermal cartographies recording :
512 pictures  10 periods
Lock-in amplifier (low signal/noise ratio on observable output) x y
Modulus
Phase lag
experimental phase lag (°)

8. Observations and signal processing
Phase lag versus ellipses axis :
several frequencies
reverse side of the sample
experimental phase lag (°)

9. Identification results
Inverse problem
quadratic criterion
Levenberg Marquardt minimization algorithm
Frequency : Hz
versus x : m2.s-1
versus y : m2.s-1

10. Identification results
f = Hz
f = Hz
f = Hz
Average
Diffusivity (x)
Diffusivity (y)
Thermal diffusivity versus z :
Hot-Disk device
versus z : m2.s-1

11. Concluding remarks
Experimental bench appears to be well adapted for identification purposes (for this class of orthotropic materials)
Periodic method is an attractive identification method in such a situation
Experimental device
reduction of measurements noises
(scanning pyrometer with oscillating mirror)
various samples
Identification method
iterative algorithm
identification versus z
Statistical investigation about identification results
relation
(fiber properties)
(matrix properties)
Multi scale analysis
microstructural properties
millimetric global estimation