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

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

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

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

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

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

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 (°)

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

Identification results Inverse problem quadratic criterion Levenberg Marquardt minimization algorithm Frequency : 0.011 Hz versus x : 7.2 10-6 m2.s-1 versus y : 8.3 10-7 m2.s-1

Identification results f = 0.021 Hz f = 0.005 Hz f = 0.011 Hz Average Diffusivity (x) 8.4 10-6 7.7 10-6 5.9 10-6 7.4 10-6 Diffusivity (y) 7. 10-7 9.2 10-7 8.6 10-7 Thermal diffusivity versus z : Hot-Disk device versus z : 1.5 10-6 m2.s-1

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