Thermal characterization of anisotropic media in photothermal point, line, and grating configuration

This article is dedicated to the simulation of heat diffusion in layered anisotropic materials. The three-dimensional heat diffusion equation for layered, anisotropic materials is used to calculate a laser induced dynamic temperature distribution, the so-called thermal-wave field, in composites. In the case of isotropic materials, the thermal-wave distribution is always axisymmetric around the center of the heat source. In multilayered fiber reinforced composites, however, the distribution of the thermal-wave field depends on their characteristic stacking sequence as well as on the geometry and the frequency of the source. Together with undergoing experimental work, these theoretical simulations allow us to compare the feasibility of different spatial excitation geometries, namely, point source, line source, and grating source, to determine the thermal conductivity tensor of composite materials. It is proven that the use of a grating suppresses the ill posedness of the inverse problem and simplifies the procedure used for the determination of the thermal properties.