The ability to image strain fields in composite materials is an indispensable necessity for structural health monitoring. Embedded electromagnetic metamaterials sensitive to applied stresses and operating in the terahertz regime have been proposed as a solution, but they have traditionally relied on slight amplitude or frequency shifts of their terahertz spectral resonance relative to a presumably unchanging, unstrained reference spectral map. Here, we demonstrate a facile, reference-free imaging technique to map the currently active local strain throughout a composite structure using a reversible passive terahertz metamaterial laminate with a tailored polarimetric signature. Only two orthogonal polarizations and a few frequencies are required to measure this strong terahertz response, from which the local strain environment may be rapidly and quantitatively mapped over large areas.

中文翻译：

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使用太赫兹超材料层压板绘制有源应变

对复合材料中的应变场进行成像的能力是结构健康监测不可或缺的必要条件。嵌入式电磁超材料对施加的应力敏感并在太赫兹范围内工作已被提出作为解决方案，但它们传统上依赖于其太赫兹光谱共振相对于可能不变的、无应变的参考光谱图的轻微幅度或频率偏移。在这里，我们展示了一种简便的、无参考的成像技术，使用具有定制极化特征的可逆无源太赫兹超材料层压板来绘制整个复合结构中当前有源局部应变。只需要两个正交极化和几个频率来测量这种强烈的太赫兹响应，