In this research, we attempt to establish a reliable structural health monitoring technique for composite materials by combining phase-shifted fiber-optic Bragg grating sensing with the laser ultrasonic visualization technology. In the first part of this article, a novel cross-adhesion configuration is designed to resolve the directionality problem of the phase-shifted fiber-optic Bragg grating ultrasonic sensing. In the adhesion configuration, Lamb waves are guided by an orthogonally bonded optical fiber from the adhesion point to the phase-shifted fiber-optic Bragg grating sensor. The analysis of the ultrasonic measurement results reveals that the proposed adhesion method enables us to use one sensor to receive Lamb waves in all in-plane directions with similar magnitude because two wave components propagating along with the two orthogonal directions are guided to the phase-shifted fiber-optic Bragg grating sensor and exhibit a linear superposition in the sensor. This simplified configuration gives our method an advantage over the existing approaches, such as the rosette configuration in which three or more phase-shifted fiber-optic Bragg grating sensors are required to relieve the sensing directionality. The phase-shifted fiber-optic Bragg grating ultrasonic sensor with the proposed adhesion configuration is then applied to visualize the propagation of ultrasonic waves in aluminum plates and carbon fiber–reinforced plastic laminates. Those verification experiments also show us that the new adhesion configuration is effective at protecting the phase-shifted fiber-optic Bragg grating ultrasonic measurement from the sensing directionality. Meanwhile, the broad bandwidth of the phase-shifted fiber-optic Bragg grating sensor enables us to visualize the propagation behavior of various Lamb wave modes over a broad frequency range. Finally, we also validate that the ultrasonic visualization technique merged with the phase-shifted fiber-optic Bragg grating ultrasonic sensing can be used to identify the hidden damage in the carbon fiber–reinforced plastic composite.

中文翻译：

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使用具有改进粘附配置的光纤布拉格光栅超声传感器的激光超声可视化技术

在这项研究中，我们试图通过将相移光纤布拉格光栅传感与激光超声可视化技术相结合，建立一种可靠的复合材料结构健康监测技术。在本文的第一部分中，设计了一种新颖的交叉粘附配置来解决相移光纤布拉格光栅超声传感的方向性问题。在粘附配置中，兰姆波由正交结合的光纤从粘附点引导到相移光纤布拉格光栅传感器。超声波测量结果的分析表明，所提出的粘附方法使我们能够使用一个传感器在所有面内方向上接收具有相似幅度的兰姆波，因为沿两个正交方向传播的两个波分量被引导到相移的光纤布拉格光栅传感器并在传感器中表现出线性叠加。这种简化的配置使我们的方法比现有方法更具优势，例如需要三个或更多相移光纤布拉格光栅传感器来减轻传感方向性的花环配置。然后应用具有建议粘附配置的相移光纤布拉格光栅超声波传感器来可视化超声波在铝板和碳纤维增强塑料层压板中的传播。这些验证实验还向我们表明，新的粘附配置可有效保护相移光纤布拉格光栅超声测量不受传感方向性的影响。同时，相移光纤布拉格光栅传感器的宽带宽使我们能够在很宽的频率范围内可视化各种兰姆波模式的传播行为。最后，