In the simulated vacuum environment of low-temperature and low-pressure, a continuous laser irradiation effect experiment of 1070 nm was carried out on a carbon fiber composite sandwich structure with white paint on the surface of the reflector antenna using a fiber laser as the light source and the morphology characteristics of sandwich structures under different laser loading conditions were obtained. The transient temperature field on the surface of the sandwich was measured by a high temperature infrared imager, and the surface temperature rise of the sandwich was obtained by thermocouple. The relationship between temperature and damage morphology of structural materials was obtained by analyzing the changes of surface temperature field and morphology during laser irradiation. The mechanism of laser action on the sandwich structure of carbon fiber composite and the influence of laser parameters on the morphology of structural materials were studied. The results show that under laser irradiation with a laser power density of about 20 W/cm2, the white paint sprayed on the surface of the front skin first ablates and falls off. As the temperature rises, the resin base of the carbon fiber composite is pyrolyzed, the carbon fiber spallation occurs, the front skin loses its mechanical properties, the rubber film is pyrolyzed, the front skin is separated from the aluminum honeycomb, and the back skin expands and deforms under the action of pyrolysis gas.
According to the principle of reflectivity measurement using cavity ring-down spectroscopy, the origin of reflectivity measurement uncertainty was analyzed, we particularly discussed the origin of ring-down time measurement uncertainty, and concluded that the maximum amplitude selection of ring-down curve, the fitting of curve, the time delay of detector, and the dispersity of measurement results were the reasons why. Based on the cavity ring-down spectroscopy method, we built a reflectivity measurement system with the wavelength of 1.319 micron, and obtained the ring-down times of straight and folded cavity respectively. According to the origin of uncertainty, the extensional uncertainty of system was obtained. The result showed the high precision of reflectivity measurement using cavity ring-down spectroscopy.
The spot profile and intensity distribution of output beam from unstable resonator of a DF Laser were measured. The results showed the spot was a ring with 45mm external diameter and the measurement data sufficed for the design requests. But the spot was asymmetric seriously on horizontal direction, which was arose by two possible reason, one was non-uniform distribution of the gain medium , the other was the optic-axis migration to upstream of gain medium.
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