Health monitoring of composite materials using dual sensing fiber Bragg grating systems

近年来，通过内置传感器监测结构状况的智能结构引起了人们的关注。在包括使用传统技术检测冲击载荷和损伤的智能结构中，将安装应变片和压电传感器。然而，这些电传感器具有严重的缺点，它们遭受电磁干扰，并且不能在爆炸环境中使用。此外，它们还需要单独的电缆。因此，应用于进行多点传感的大型结构的监测系统将不可避免地包括复杂的电缆网络。为了克服这些技术困难，具有多功能、多灵活性和抗电磁干扰能力的光纤布拉格光栅（Fiber Bragg Grating，FBG）有望成为结构健康监测的有前途的传感器，本研究的目的是开发一种简单的既能测量应变又能检测超声的光纤布拉格光栅传感系统 关于我们 用于结构健康监测。基于波长-光强转换技术，利用光纤光栅构成了一种应变和超声检测的光纤系统。该光纤光栅传感系统由宽带光源、用于应变测量的宽带滤光片和用于超声检测的窄带可调谐滤光片组成。将该系统应用于碳纤维复合材料的冲击应变测量和冲击损伤检测，实验结果表明，光纤光栅和普通应变计的最小可测应变分别为1.2με和8.1 με，信噪比分别为40 dB和8dB。光纤光栅传感器具有自参考和抗电磁干扰的特性，在长期应变测量中具有很高的可靠性。此外，使用可调谐滤波器使超声波灵敏度最大化的超声波检查可以检测到6.3X9mm^2的冲击损伤。这些实验结果证实了光纤光栅传感系统可以用于监测复合材料中的应变和损伤。少

Smart structures in which structural conditions are monitored with built-in sensors have drawn attention in these days. In smart structures including detection of both impact loading and damage using conventional technique, strain gauges and piezoelectric sensors would be installed. However, these electric sensors have serious drawbacks that they suffer from electromagnetic interference and cannot be used in explosive environment. Moreover, they need individual cables. Therefore, the monitoring system applied to large-scale structures where multi-point sensing is performed would inevitably include complex cable network. In order to overcome these technical difficulties, fiber Bragg gratings (FBGs) featuring multifunction, multiplexibility as well as immunity to electromagnetic interference have been expected to be promising sensors for structural health monitoring.The objective of the present study is to develop a simple FBG sensing system which can measure strain and detect ultrasound … More for structural health monitoring. A fiber-optic system featuring strain measurement and ultrasonic detection was constructed with fiber Bragg gratings based on wavelength-light intensity conversion technique. This fiber Bragg grating sensing system consists of a broadband light source, a broadband optical filter for strain measurement and a narrowband tunable filter for ultrasonic detection. The system was applied to strain measurement in impact loading to carbon fiber-reinforced plastics and the subsequent impact damage detection.Experimental results proved that the minimum detectable strain for FBG and conventional strain gauge are estimated to be 1.2με and 8.1.με, and signal-to-noise ratios are evaluated to be 40dB and 8dB, respectively. FBG sensors would be highly reliable in long-term strain measurement because of its self-referencing and immunity to electromagnetic interference. Furthermore, ultrasonic inspection in which ultrasonic sensitivity was maximized using the tunable filter could detect a 6.3X9mm^2 impact damage. These experimental results have confirmed that the FBG sensing system can be useful tools to monitor strain and damage in composite materials. Less