1 September 1993 Absolute optical absorption spectra in graphite epoxy by Fourier transform infrared photoacoustic spectroscopy
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Abstract
Optical absorption is obviously of prime interest in the efficiency of laser generation of ultrasound in graphite-epoxy laminates. However, no quantitative spectrum of optical absorption in this composite material has yet been published in the literature. Transmission techniques are inefficient, and other techniques, like attenuated total reflectance or diffusive reflectance, do not give absolute values. The Fourier transform photoacoustic spectroscopy technique seems to be a good alternative that can analyze adequately and quantitatively a graphite-epoxy laminate. We used three different methods to compute the absolute optical absorption from the photoacoustic signal. The three methods are: the saturation of the real part of the photoacoustic spectrum, the comparison of the spectra obtained with two different mirror velocities, and the calibration of the photoacoustic cell with a transmission measurement. The spectra obtained in the IR band of 2.5 to 25 μm are presented, and the problems and limitations of each method are discussed. The results permit a better understanding of the absorption process in the composite laminate, and in this way, will help us enhance the efficiency of laser generation of ultrasound in graphite epoxy.
Marc Dubois, Marc Choquet, Jean-Pierre Monchalin, Franck Enguehard, Lionel Bertrand, "Absolute optical absorption spectra in graphite epoxy by Fourier transform infrared photoacoustic spectroscopy," Optical Engineering 32(9), (1 September 1993). https://doi.org/10.1117/12.145067
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