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Time resolved spectroscopic temperature measurement techniques during CW-laser matter interaction of glass–fiber-reinforced-polymers (GFRP)
Author(s): H. Borchert; V. Allheily; L. Merlat; R. Schmitt
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Paper Abstract

Composite materials (GFRP) have shown a significant increase in their use for aerospace and military applications in recent years. Concurrent maturation of the technology in near Infrared High Energy Lasers has proven to be promising for use in directed energy weaponry. The binding matrix of many common aerospace composite materials are made of polymeric materials. The thermodynamics of GFRP as well as the thermo-mechanical behavior of such heterogeneous materials submitted to a typical laser weapon irradiation need therefore to be further explored to understand precisely the deterioration process induced by the illumination. Front and side views during the HEL (High Energy Laser) interaction process with the GFRP target material at different time delays clearly evidence the complicated nature of smoky plume and flame combustion creation during the irradiation process. During the energy deposition rise of the continuous laser wave, the GFRP target heats up due to absorption in the outer epoxy layer. Further increase of the energy reveals a smoky plume optically thin directly above the surface of the GFRP-target. Time resolved emission spectroscopy was used to investigate the chemical decomposition and surface temperature in the low and high temperature regime during the laser matter interaction process. The spectral emission in the visible range is dominated by continuum emission which provides the distribution temperature in time based on Planck`s law. In the low temperature regime (infrared wavelength bands from λ = 2μm up to λ = 11μm) a four channel infrared detector system was designed to retrieve the distribution temperature. The experimental, time resolved signal from four different infrared detectors at center wavelengths of λ = 3.348 μm, λ = 4.49 μm, λ = 7.41 μm and λ = 10.57 μm are used to reconstruct the Planck-function by a fitting routine with the temperature as parameter. The calibration of the system was made with a conventional Black-body source PY5. The obtained temperature distribution in time was then compared to measurements with a conventional pyrometer. With the concept of this four channel detector we overcome the difficulties of acquisition speed and single band nature of conventional pyrometers.

Paper Details

Date Published: 7 October 2019
PDF: 11 pages
Proc. SPIE 11162, High Power Lasers: Technology and Systems, Platforms, Effects III, 111620M (7 October 2019); doi: 10.1117/12.2532324
Show Author Affiliations
H. Borchert, Institut Franco-Allemand de Recherches de Saint-Louis (France)
V. Allheily, Institut Franco-Allemand de Recherches de Saint-Louis (France)
L. Merlat, Institut Franco-Allemand de Recherches de Saint-Louis (France)
R. Schmitt, Institut Franco-Allemand de Recherches de Saint-Louis (France)


Published in SPIE Proceedings Vol. 11162:
High Power Lasers: Technology and Systems, Platforms, Effects III
Harro Ackermann; Willy L. Bohn; David H. Titterton, Editor(s)

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