Invited Article A Theoretical Model for the Measurement of Fiber Orientation with Thermal Waves

It is an important task of nondestructive testing to determine the fiber orientation of reinforced polymers. One appropriate method, especially for carbon fibers, is phase-sensitive modulated thermography, where images of the phase angle and the amplitude of thermal waves at the surface of the sample are obtained. The anisotropy induced by the fibers results in elliptical contour lines whose direction and excentricity are correlated with the orientation of the fibers and the corresponding degree of thermal anisotropy, respectively.