TY - CHAP A1 - Dengler, Simon Andreas A1 - Roseeu Gonzalez, R. V. A1 - Luber, M. A1 - Ziemann, Olaf A1 - Engelbrecht, Rainer A1 - Schmauss, B. T1 - Performance Evaluation of Reference Reflections in Polymer Optical Fibers for Strain Sensing T2 - 27th International Conference on Optical Fiber Sensors N2 - We present a robust concept for quasi distributed strain measurement using optical time domain reflectometry (OTDR) in polymer optical fibers (POF). The spatial shifts of discrete reflective events in the OTDR trace are evaluated as reference points. It is shown how such reference reflections can be prepared and which properties can be expected. Y1 - 2022 SN - 978-1-957171-14-2 U6 - https://doi.org/10.1364/ofs.2022.tu2.6 PB - Optica Publishing Group CY - Washington, D.C. ER - TY - CHAP A1 - Dengler, S. A1 - Schmidt, N. A1 - Luber, M. A1 - Fischer, J. A1 - Ziemann, Olaf A1 - Engelbrecht, Rainer A1 - Hangen, H. T1 - B8.3 Influence of Temperature on Distributed Strain Sensing with OTDR in Polymer Optical Fibers T2 - SMSI 2021 - Sensors and Instrumentation N2 - Strain in ground and earthworks can be measured by polymer optical fibers (POF) applied to geotextiles. We measure the increase of backscatter (IOB) in the fiber under strain using optical time domain reflectometry (OTDR). The effect of temperature on this measurement principle is investigated. The local backscatter changes by 0.003 dB/K for common ambient temperature. In addition it is shown, that temperature depended viscoelastic properties of the polymer does affect IOB. KW - optical time domain reflectometry, structural health monitoring, strain sensing, geotextiles, polymer optical fib Y1 - 2021 SN - 978-3-9819376-4-0 U6 - https://doi.org/10.5162/smsi2021/b8.3 SP - 155 EP - 156 PB - AMA Service GmbH, Von-Münchhausen-Str. 49, 31515 Wunstorf, Germany ER - TY - JOUR A1 - Weiland, J. A1 - Luber, M. A1 - Seewald, R. A1 - Schiebahn, A. A1 - Engelbrecht, Rainer A1 - Reisgen, U. T1 - Structural Health Monitoring of Adhesively Bonded Joints: Proposing a new Method by use of Polymer Optical Fibers JF - Procedia Structural Integrity N2 - According to the current state of the art, adhesively bonded joints cannot be tested completely non-destructively. This is the main motivation to permanently monitor adhesively bonded joints in order to record their structural integrity and - as a result - to ensure safe load transmission. By the use of permanent non-destructive Structural Health Monitoring (SHM) methods, structural damages in the adhesive bond can be detected at an early stage. This paper presents a new method for monitoring the structural integrity of adhesively bonded joints by integrating a Polymer Optical Fiber (POF) into the adhesive layer. The sensor concept is based on a deformation transfer from the adhesive to the POF, which results in a change in the cross-sectional shape of the POF. The cross-sectional shape influences the optical light propagation in the POF, which can be detected by simple optical measuring devices. The paper describes the general principle and first results of investigations on a structural adhesive (3M Scotch-Weld DP 609). The sensor signal is in a good relation to the stress state of the adhesive layer. KW - adhesive bonding structural health monitoring polymer optical fiber single lap joint Y1 - 2020 U6 - https://doi.org/10.1016/j.prostr.2020.11.106 SN - 2452-3216 VL - 28 SP - 1249 EP - 1257 PB - Elsevier BV ER - TY - CHAP A1 - Engelbrecht, Rainer A1 - Rostan, K. A1 - Weiland, J. A1 - Luber, M. A1 - Schiebahn, A. A1 - Reisgen, U. T1 - Modal Distribution in Polymer Optical Fibers as Sensor for Load Monitoring in Semi-Structural Adhesive Bonds T2 - 27th International Conference on Optical Fiber Sensors N2 - PMMA polymer optical fibers embedded in semi-structural polyurethane adhesive bonds serve as economical load sensor for structural health monitoring by evaluating load-dependent optical transmission as well as modal distribution measured by a far-field camera. Scaling of sensor quantities by the sensitive fiber length is shown. Y1 - 2022 U6 - https://doi.org/10.1364/ofs.2022.w2.3 PB - Optica Publishing Group CY - Washington, D.C. ER - TY - JOUR A1 - Weiland, J. A1 - Bartholomee, W. A1 - Luber, M. A1 - Schiebahn, A. A1 - Engelbrecht, Rainer A1 - Reisgen, U. T1 - Investigation into the mechanical behavior of a polymer optical fiber embedded in a structural adhesive JF - International Journal of Adhesion and Adhesives N2 - To guaranty a safe load transfer through adhesively bonded joints, Structural Health Monitoring (SHM) methods that allow for permanent monitoring of the structural bond condition, are becoming more and more important. To meet this increasing demand, a novel approach for SHM of adhesively bonded joints by use of integrated Polymer Optical Fibers (POF) has been demonstrated in previous work. The sensor operating principle is based on strain transfer from the structural adhesive to the integrated POF. This strain transfer leads to a deformation of the POF cross-sectional shape and in that way affects the optical light propagation in the POF. In the current work, numerical and experimental results are presented into the mechanical behavior of embedded POF in adhesive bulk specimens subjected to tensile loading. Local deformations of both the POF (Asahi Kasei DB 500) and the structural adhesive (3 M Scotch Weld DP410) are evaluated using Digital Image Correlation (DIC). In the loading direction, a linear correlation is shown between strain inside the POF core and strain of the surrounding adhesive. Tests results, as well as fracture analysis, show a highly ductile behavior and failure of the POF cladding material and the interface between the POF core and annular cladding. KW - Structural health monitoring SHM Polymer optical fibers POF Epoxy Digital image correlation Finite element modelling Y1 - 2022 U6 - https://doi.org/10.1016/j.ijadhadh.2021.103018 SN - 0143-7496 VL - 117 PB - Elsevier BV ER - TY - CHAP A1 - Engelbrecht, Rainer A1 - Dengler, S. A1 - Luber, M. A1 - Fischer, J. A1 - Hangen, H. T1 - SHM at Giant Mine Heaps by OTDR Sensing with Polymer Optical Fibers BT - Chances and Challenges from Field Campaigns T2 - Optical Fiber Sensors Conference 2020 Special Edition N2 - Results from field measurement campaigns for structural health monitoring (SHM) at giant mine heaps by optical time domain reflectometry (OTDR) in polymer optical fibers (POF) are presented. Polymer geogrids built for soil reinforcement are fitted with POF for strain sensing as part of a geosynthetic sealing system designed to protect the heap from infiltration of surface water. Strain is detected by a local increase of backscatter. Measurements on eight sensor lines have been performed over a time period of six months to monitor the system behavior and potential development of or cracks within the underlying base of a sealing system. Results show the usability of this technology for strain sensing and SHM in such a harsh environment. Challenges still exist in the quantitative evaluation of the fiber sensor data due to cross sensitivity to fiber bending and lateral pressure. Y1 - 2021 U6 - https://doi.org/10.1364/ofs.2020.th4.7 PB - Optica Publishing Group CY - Washington, D.C. ER -