Based on published values of the complex refractive index of graphite and the assumption that the surface of carbon fibers consists of concentric graphite layers Christian Freitag (IFSW) has calculated the polarization and wavelength dependent absorptance of laser radiation on carbon fibers, carbon fiber preforms and CFRP by means of ray tracing. The absorptance of carbon fiber preforms has a local maximum in the wavelength range between 355 nm and 532 nm of about 82% for a polarization perpendicular to the axis of the fibers (78% for polarization parallel to the fibers). The absorptance drops to values below 50% for wavelengths around 10.6 µm. As long as the matrix is not removed the wavelength dependence of the absorptance in CFRP is much less pronounced. In this case the absorptance amounts to about 80% in the wavelength range between 600 nm and 1100 nm with a slight increase for wavelengths between 450 nm and 600 nm.
More details on the model and the results are published by Christian Freitag et al. in „Polarization dependence of laser interaction with carbon fibers and CFRP”, Optics Express 22 (2), 1474-1479 (15. January 2014).
Contact: Dr. Rudolf Weber