以內埋式光纖光柵感測器監測膠合修補碳纖維複合材料衝擊損傷之應用

Abstract

碳纖維強化複合材料(Carbon fiber reinforced plastics，CFRP)因為擁有良好的機械性質，因此在目前廣泛的運用於各種領域。所以當複合材料結構內部的衝擊損傷產生後要如何修補與監測複合材料結構內部的損傷發展，便成為避免發生劇烈的結構破壞所要探討的課題。因為布拉格光纖光柵(Fiber Bragg Grating，FBG)尺寸小，所以埋入複合材料內部後相容度高，並可以用來監測複材內部破壞的發展。本篇論文的目的就是要探討內埋式FBG感測器對於監測複合材料內部衝擊損傷後膠合修補成效的可行性。從衝擊後疲勞實驗的結果發現，寬頻光源經過內埋在複合材料內FBG所反射的光譜波形波峰，有隨著疲勞週期的增加而強度逐步下降的現象。有時也發生FBG在強大應變場下造成波形外波長上升將波峰淹沒的現象，但是整體而言FBG的反射波峰強度是判斷損傷發展的可考依據。因此我們以波峰強度下降幅度來判斷修補衝擊損傷後疲勞實驗的結果，可以發現修補後的波峰強度下降幅度小於未修補，這便證明了膠合修補有抑制損傷發展的功用。在膠合修補衝擊後疲勞損傷再疲勞實驗中也指出，經過膠合修補的FBG反射波峰強度維持穩定。所以使用內埋式FBG感測器來監測複合材料內部的損傷與判斷膠合修補的成效是可行的。

Carbon fiber reinforced plastics (CFRP) are used in various fields, due to their high specific strength and modulus. Interior damage in CFRP caused by impact may lead to catastrophic failure of the structure. Patching repair is sometimes employed. It is important to monitor the damage development after repair to make sure that the CFRP structure is reliable and safe. Due to its small size, Fiber Bragg Grating (FBG) sensors can be embedded inside the CFRP materials without significantly affecting its integrity. The purpose of this study was to discuss the feasibility of investigating impact damage development and the effect after composite patch repair (CPR) by using pre-embedded FBG sensor in CFRP material. For the post-impact fatigue test, it was found that the intensity of FBG peak gradually decreased as the fatigue cycles increase. Occasionally, in the highly non-uniform strain filed near the FBG, the disappearance or near vanish of peak was caused by other wavelength intensity increasing. As a whole, variation of intensity of the peak can be used to reflect the damage development. Thus, comparing with result of CPR impact damage before fatigue test, it proves damage development was restrained by use patch repair. It was same result for CPR post-impact fatigue damage before second fatigue test, intensity of peak kept stable. In other words, pre-embedded FBG sensor in CFRP material is able to monitor damage development inside CFRP and to prove CPR can restrain damage development.