| Popis: |
Laser-ultrasonics is now recognized as an advantageous technique for polymer-matrix composite inspection, especially in the aircraft industry where composite component shapes become more and more complex. In the aircraft industry, the generation laser of choice is the CO2 laser for different reasons: its wavelength is strongly absorbed in most polymers, relatively high repetition rates can be achieved at relatively high energy, and commercial vendors provide products suitable to industrial environments. However, CO2 lasers also suffer from a certain number of drawbacks: the wavelength is not suitable to fiber delivery, temporal modulation of the pulse is hardly possible, and very high repetition rates cannot be achieved. This paper presents the results of a numerical study to determine the optimum generation-laser parameters. A comprehensive numerical model of laser-generation of ultrasound was used to study the effects of optical penetration depth and generation-laser temporal profile on the amplitude of the generated longitudinal waves while considering damage threshold mechanisms. This study concluded that the CO2 laser can be advantageously replaced to improve sensitivity, reliability, and productivity for the inspection of polymer-matrix composites. |
