MS&P: Optical Fiber Sensors for In-Situ Temperature and Strain Measurements in Composite

光纤传感器将被开发用于高温(1000摄氏度)加工的复合材料中。具体地说，新型光纤将用于两种类型的现场测量：温度和污渍。温度传感器将与稀土掺杂剂合成，使空间分辨率温度测量在500-500范围内-1200摄氏度。基于法布里-珀罗(Fabry-Perot)光栅的应变传感器和使用光时域反射仪的应变传感器都将被研究。开发的温度和应变传感器将被结合到纤维增强材料中，将通过化学气相渗透(CVI)生产的陶瓷和金属间化合物基复合材料。因为这些材料已经含有纤维，加入额外的光纤传感器不会对微结构产生明显的干扰。目前正在开发各种先进的、热梯度CVI工艺，作为该计划的一部分，将开发的光纤传感器将使监测加工过程中的温度梯度成为可能。一种相对简单的热梯度CVI系统将用于在复合材料过程中进行光纤温度的现场测量捏造。这些材料的微观结构也将被定量表征，并建立了渗流过程的数值模型，分析了渗流过程中的温度梯度和组织演变。模拟计算和实验测量之间的比较将提供对渗透过程的洞察，并展示了使用光纤温度传感器的潜力。应变传感器将在加工过程中提供测量，更重要的是，它们将使在使用复合材料时测量应变成为可能。这些现场应变测量为研究材料的应力-应变行为提供了一种新的方法。在脆性基复合材料中，基质相通常在材料失效之前很久就开始微裂纹，因此，这些现场应变测量特别重要，因为在此之前可以监测这些材料的降解情况宏观失灵实际上是存在的。

Optical fiber sensors will be developed for applications in composite materials that are processed at high-temperatures (1000oC). Specifically, novel optical fibers will be used for two types of in-situ measurements: temperature and stain. Temperature sensors will be synthesized with rare-earth dopants that will permit spatially resolved temperature measurements in the range of 500- 1200oC. Strain sensors based on Fabry-Perot gratings and using optical time domain reflectometry will both be investigated. The temperature and strain sensors that are developed will be incorporated in fiber-reinforced, ceramic and intermetallic matrix composites that will be produced by chemical vapor infiltration (CVI). Because these materials already contain fibers, the incorporation of additional optical fiber sensors will not significantly perturb the microstructure. A variety of advanced, thermal gradient CVI processes are currently being developed, and the optical fiber sensors that will be developed as part of this program will make it possible to monitor temperature gradients during processing. A relatively simple thermal gradient CVI system will be used to make in- situ optical fiber temperature measurements during composite fabrication. The microstructure of these materials will also be characterized quantitatively, and a numerical model of the infiltration process will be developed to analyze both the temperature gradients and the microstructure evolution. Comparisons between the modeling calculations and the experimental measurements will provide insight into the infiltration process, and demonstrate the potential for using optical fiber temperature sensors. The strain sensors will provide measurements during processing, and more importantly, they will make it possible to measure strain when the composite is in use. These in-situ strain measurements offer a novel method to study the stress-strain behavior of the material. In brittle matrix composites, the matrix phase typically begins to microcrack long before the material fails, thus these in-situ strain measurements are particularly important because it will be possible to monitor the degradation of these materials before macroscopic failure actually occurs.