This work aims at radar sensors in the frequency band from 57 to 64 GHz that can be embedded in wind turbine blades during manufacturing, enabling non-destructive quality inspection directly after production and structural health monitoring (SHM) during the complete service life of the blade. In this paper, we show the fundamental damage detection capability of this sensor technology during fatigue testing of typical rotor blade materials. Therefore, a frequency modulated continuous wave (FMCW) radar sensor is used for damage diagnostics, and the results are validated by simultaneous camera recordings. Here, we focus on the failure modes delamination, fiber waviness (ondulation), and inter-fiber failure. For each failure mode, three samples have been designed and experimentally investigated during fatigue testing. A damage index has been proposed based on residual, that is, differential, signals exploiting measurements from pristine structural conditions. This study shows that the proposed innovative radar approach is able to detect continuous structural degradation for all failure modes by means of gradual signal changes.

中文翻译：

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疲劳试验期间基于雷达的玻璃纤维增​​强复合材料监测

这项工作的目标是在 57 至 64 GHz 频段内的雷达传感器可以在制造过程中嵌入风力涡轮机叶片中，从而在生产后直接进行无损质量检查，并在叶片的整个使用寿命期间进行结构健康监测 (SHM) . 在本文中，我们展示了这种传感器技术在典型转子叶片材料的疲劳测试过程中的基本损伤检测能力。因此，使用调频连续波 (FMCW) 雷达传感器进行损坏诊断，并通过同步摄像头记录验证结果。在这里，我们关注失效模式分层、纤维波纹度（起伏）和纤维间失效。对于每种失效模式，设计了三个样品并在疲劳测试期间进行了实验研究。已经提出了基于残余信号的损伤指数，即差分信号，利用原始结构条件的测量结果。这项研究表明，所提出的创新雷达方法能够通过逐渐的信号变化来检测所有故障模式的持续结构退化。