Derrien Nicolas, Lehujeur Maximilien, Chapeleau Xavier, Durand Olivier, Gallet Antoine, Roussel Nicolas, Yven Béatrice, Abraham Odile
Géophysique et Evaluation Non Destructive (GéoEND) Laboratory, Géotechnique, Environnement, Risques Naturels et Sciences de la Terre (GERS) Department, Université Gustave Eiffel, Nantes Campus, F-44344 Bouguenais, France.
Structure et Instrumentation Intégrée (SII) Laboratory, Inference for Structures (I4S) Team (Inria), Composants et Systèmes (COSYS) Department, Université Gustave Eiffel, Nantes Campus, F-44344 Bouguenais, France.
Sensors (Basel). 2025 Apr 23;25(9):2657. doi: 10.3390/s25092657.
Fiber optic sensors are increasingly used to measure dynamic strain fields caused by the propagation of mechanical waves. Their low intrusiveness when embedded within a structure makes them suitable for a wide range of applications. In this paper, the feasibility of integrating fiber Bragg gratings (FBGs) into castable materials for ultrasonic applications is investigated. We employed castable polyurethane resins, which are widely used in industry due to their reproducible and durable mechanical properties. Our study began with an analysis of fiber integration by examining the 1D strain profiles of two polyurethane resins during their polymerization and also the impact of their hardening on the central wavelength value of several FBGs spectra. Subsequently, we assessed the sensitivity of FBGs to ultrasonic waves generated at 100 kHz after resin polymerization. Specifically, we explored how the fiber coating influences the rate of energy transfer from the host material to the fiber core. Our findings demonstrate that the central wavelength shift in the FBG reflectivity spectra, caused by shrinkage during resin polymerization, can reach up to 10 nm. This shift must be considered when selecting FBG wavelengths to prevent the reflectivity spectra from falling outside the permissible range of the interrogation system. We measured exploitable ultrasonic waves propagating in the resin samples. Preliminary observations suggest the presence of early arrivals, which could potentially correspond to crosstalk effects between the FBGs even though they are centered at different wavelengths. Furthermore, we show that in dynamic strain fields caused by ultrasonic wave propagation, both acrylate and polyimide coatings transmit similar amounts of energy to the fiber core. These preliminary results highlight the potential of using FBGs as ultrasonic wave sensors embedded in castable materials such as polyurethane resins.
光纤传感器越来越多地用于测量由机械波传播引起的动态应变场。当嵌入结构中时，它们的低侵入性使其适用于广泛的应用。在本文中，研究了将光纤布拉格光栅（FBG）集成到用于超声应用的可浇铸材料中的可行性。我们采用了可浇铸的聚氨酯树脂，由于其可重复和持久的机械性能，它们在工业中被广泛使用。我们的研究首先通过检查两种聚氨酯树脂在聚合过程中的一维应变分布以及它们的硬化对几个FBG光谱中心波长值的影响来分析光纤集成。随后，我们评估了树脂聚合后FBG对100kHz产生的超声波的灵敏度。具体来说，我们探讨了光纤涂层如何影响从主体材料到光纤芯的能量传输速率。我们的研究结果表明，树脂聚合过程中的收缩导致FBG反射光谱中的中心波长偏移可达10nm。在选择FBG波长时必须考虑这种偏移，以防止反射光谱落在询问系统的允许范围之外。我们测量了在树脂样品中传播的可利用超声波。初步观察表明存在早期到达信号，即使它们的中心波长不同，这也可能对应于FBG之间的串扰效应。此外，我们表明，在由超声波传播引起的动态应变场中，丙烯酸酯和聚酰亚胺涂层向光纤芯传输的能量量相似。这些初步结果突出了将FBG用作嵌入聚氨酯树脂等可浇铸材料中的超声波传感器的潜力。
