Study of Health-monitoring of Fiber Reinforced Plastic Structures Using Optical Fiber Sensors

本研究的目的是建立一套基于光纤传感器的纤维增强塑料(FRP)结构健康监测系统，用于FRP结构的损伤检测和内部应变测量。取得了以下研究成果：(1)研究了FRP层合板中埋入光纤对其力学性能的影响。在实验中，测量了埋入光纤的FRP层合板的层间剪切强度。结果表明，在FRP层合板中埋入光纤对FRP层合板的层间剪切强度有较大的影响。研究发现，埋入光纤对FRP层合板的层间剪切强度有一定的影响，且这种影响与增强纤维与光纤之间的夹角有关。在两根光纤埋入的情况下，这种影响依赖于光纤之间的埋入间隔。(2)研制了一种能够检测FRP层合板中分层和裂缝的系统。报道了几种分层检测方法。因此，本文提出了一种新的层间剪切强度检测方法。设计了一种新的分层检测方法，并将其引入到该系统中。通过冲击载荷下的分层检测试验，验证了该系统的有效性。(3)研制了一种基于迈克尔逊干涉仪的FRP内部应变测量系统。该系统基于迈克尔逊干涉仪，能够测量FRP在振动或疲劳状态下的周期性变化的应变。本研究开发了一种从干涉仪输出中获取应变的数字处理技术。通过与电应变仪测量结果的比较，验证了该系统的有效性。从上述结果来看，结果表明，利用光纤传感器构建FRP结构的健康监测是可能的。

The subject of the present study is to construct a health-monitoring system for fiber reinforced plastic (FRP) structures by which is able to detect damages and measure internal strain of FRP with optical fiber sensors.The following results have been obtained.(1) The effects of embedding optical fibers in FRP laminates on their mechanical properties have been investigated.In the experiments the interlaminar shear strength of FRP laminates in which the optical fibers were embedded was measured.As a result, it was found that embedding optical fibers affected the interlaminar shear strenght of FRP laminates and its effect depended on the angle between the reinforcing fibers and optical ones.It was also found that in the case of two optical fibers embedded, the effect depended on embedding intervals between the optical fibers.(2) A system which is able to detect delaminations and cracks within FRP has been developed.Few detecting method of the delaminations have been reported.So, a new method of detecting the delaminations was devised and introduced into this system.The validity of the system was confirmed by the detecting test of the delaminations under impact loading.(3) A system which is able to measure internal strain of FRP has been developed.This system is based on Michelson interferometer and is able to measure periodically changing strain of FRP subjected to vibration or fatigue.In this study, a digital processing technique for obtaining strain from the interferometer output has been developed.The validity of the system was confirmed by comparison between results obtained by the present system and those by the electrical strain gauge.From above-mentioned results, it has been shown that it is possible to construct the health-monitoring in FRP structures with the optical fiber sensors.