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| Non-Destructive Testing for Aerospace Composite Structures Using Laser Ultrasonic Technique |
| QIU Jinhao, ZHANG Chao, JI Hongli, TAO Chongcong |
| (State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China) |
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Abstract Aimed at solving the problem of large-area detection for aerospace laminated structures with curved surfaces, laser ultrasonic technique with non-contact measurement has attracted more and more attention. By using pulsed laser to generate the ultrasonic waves in the structures, the wave-field data can be obtained. Through analyzing the characteristics of ultrasonic wave propagation, the structural damage detection and mechanical property identification can be achieved. Focused on the widely used aerospace composite structures, this paper presents the research progress on three aspects: debonding damage detection, damage accumulation characterization and fatigue life prediction. Taking laminated composite structures as an example, the influence of debonding damage on ultrasonic wave propagation is studied. By extracting the damage index, such as wave energy and wave number, the debonding damage can be visualized. Then, the influence of matrix crack accumulation in fiber reinforced polymer on mode conversion is investigated. By defining a mode-to-mode ratio, the density of matrix cracks can be characterized. Finally, a micro-damage based fatigue evolvement model for composites is established. Through Bayesian model averaging and wave velocity measurement using laser ultrasonic technique, the fatigue life of composites can be predicted, providing foundation for non-destructive testing in aerospace composite structures.
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2020, 
