Measurement of the thermal radial diffusivity of anisotropic materials by the converging thermal wave technique
Abstract
A technique for measuring the radial thermal diffusivity of laminated (often anisotropic) materials is presented. First the surface of the sample is heated in an annular pattern, and then the temperature rise in the center of the annulus is recorded. From the experimental temperature timehistory of this point, an apparent radial diffusivity versus time curve can be plotted. It is assumed that the medium is either a thick opaque medium with no convective heat losses or a thin or transluscent medium. The apparent radial diffusivity of the curve can be obtained either by direct inversion of the experimental thermogram using the mathematical expression of the theoretical thermogram or by a technique using its logarithmic derivative with respect to time. The two methods are compared for the case of a semiinfinite medium and the general case of the sample of finite thickness with heat losses at its surface is studied numerically. Several potential sources of error in the evaluation of the thermal radial diffusivity are presented and studied numerically.
 Publication:

Materials Science and Engineering
 Pub Date:
 1990
 Bibcode:
 1990MSEng...5..127E
 Keywords:

 Anisotropic Media;
 Composite Materials;
 Nondestructive Tests;
 Thermal Diffusivity;
 Thermal Radiation;
 GraphiteEpoxy Composites;
 Laminates;
 Thermal Conductivity;
 Instrumentation and Photography