Influence of test conditions on the accuracy of laser flash measurements
Jürgen Blumm, Stephanie Lemarchand
The laser flash method (Parker et al, 1961 J. Appl. Phys. 32 1679 – 1684) is a well-known technique for measurements on materials with high thermal diffusivities. The advantages of this non-contact measurement technique are, among others, easy sample preparation, fast measurement times, small sample dimensions, and high accuracy. The energy and shape of the laser pulse used for heating the front face of the sample can have a significant influence on the results. The influence of pulse length can be taken care of by an accurate pulse-length correction (Azumi and Takahaski, 1981 Rev. Sci. Instrum. 52 1411 – 1413) based on the real shape of the laser pulse. It is shown here that, after the pulse-length correction, the thermal diffusivity is independent of the length of the employed laser pulse for samples with standard dimensions. On the other hand, the employed laser energy can have an influence on the results in the case of samples with strongly temperature-dependent thermal diffusivity. The influence of the pulse energy on the results for various kinds of carbon samples is investigated and a correction routine for its effect is presented.