Distributed Fiber Optics Sensing Applied to Laminated Composites: Embedding Process, Strain Field Monitoring with OBR an
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Distributed Fiber Optics Sensing Applied to Laminated Composites: Embedding Process, Strain Field Monitoring with OBR and Fracture Mechanisms G. Souza1 · J. R. Tarpani1 Received: 9 May 2020 / Accepted: 3 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Optical fibers (OFs) are among the most promising technologies for distributed sensing in structure health monitoring of composites. Optical backscatter reflectometer (OBR) based on Rayleigh scattering enable to use the entire length of telcom OF as sensor, giving detailed information about the stain fields in the host structure. Embedded sensors can provide many advantages over surface bonded ones in terms of reliability and accuracy of the measurements. Here, OFs were embedded in between (0/0), (0/90) and (90/90) interfaces of a [ 02/902/02] glass fiber reinforced polymer (GFRP) and were further interrogated with OBR during tensile tests. Sensors were evaluated in terms of its sensing capabilities and fracture mechanism. OFs aligned in between (0/0) direction endured 5500 µε and deviated only 2.7% in the Young’s modulus calculation compared to mounted strain gauges. The other directions presented problems related to matrix rich area (0/90) and air bubbles imprisoning (90/90), reducing the sensing range. After reaching the cracking state, OFs fail progressively and are still capable of acting as sensor, as was showed in a simple visible laser scattering test. For the first time, embedding, interrogation with OBR and fracture mechanisms are approached in a single study, which provide valuable information for wide application of OFs in SHM. Keywords Structure health monitoring (SHM) · Optical fibers (OF) · Optical backscatter reflectometer (OBR) · Embedding sensors · Vacuum assisted resin infusion (VARI)
1 Introduction Information about the strain field and the detection of barely visible damage (BVID) at real time and using specific monitoring techniques of Structural Health Monitoring (SHM) has enabled a better understanding about the mechanical behavior of fiber reinforced composites, mainly regarding to failure [1, 2]. As a result, less conservative designs of composite parts are foreseen in the near future, using its the full potential on developing lightweight structures [3]. Moreover, this could avoid unnecessary maintenance as inspections would be performed as a function of the real state instead of periodic time based inspections, reducing costs and saving
* G. Souza [email protected] 1
Department of Materials Engineering, Engineering School of São Carlos - University of São Paulo (SMM-EESC-USP), São Carlos, SP 13566‑590, Brazil
time, which would lead to the widespread use of high performance composite materials to daily applications [4–6]. Among the wide possibilities of SHM, optical fibers (OFs) has gained much prominence due its very attractive characteristics as its small size, lightweight, inertia in the presence of electric or magnetic field and corrosion resistance [2, 7]. In fact, Fiber Bragg
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