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Repair Patch Monitoring with Embedded Optical Sensors by the Residual Strain Release

Abstract : Repair of metal structures with carbon fibre reinforced plastic (CFRP) patches has a high potential for aeronautic structures. Bonded repairs with CFRP offer the advantage within others to repair in places where a standard riveted repair is not possible due to space limitations or geometrical conditions. It is of vital importance that a bonded repair patch will not peel off during service. Monitoring the patches provides a tool to detect a debond of the repair patch before the debond becomes a critical issue. A monitoring technique has been studied that enables to detect a patch peel off using fiber optic Bragg grating sensors (FBGS) embedded in the CFRP-patch. Temperature compensation has been introduced to enable the application of this technique in a wide temperature range. The technique allows the monitoring of the patch on ground after a defined number of flight cycles. The viability of the monitoring principle was studied and demonstrated on seven specimens made of typical aeronautic aluminum with bonded CFRP patches that are instrumented with two or four embedded FBGS. The results of the tests show that the embedded sensors can indeed sense the debonding of a bonded CFRP patch used to repair an aluminum structure. The sensitivity of the sensors is sufficiently high to detect a crack front that is still 10 mm far from the sensor. The temperature effect on the embedded sensors that monitors the crack front can be compensated by a second sensor that is far from the sensor front. A robust pre-cured sensor mat design was developed and manufactured. This sensing mate was made using four three fibers each with four FBGSs, embedded between two glass fabric plies, providing repeatable, easy and robust sensor integration. Test structures with monitored composite repair pat
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Submitted on : Thursday, July 10, 2014 - 9:48:11 AM
Last modification on : Thursday, August 16, 2018 - 9:24:01 AM
Long-term archiving on: : Friday, October 10, 2014 - 10:45:31 AM


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  • HAL Id : hal-01021996, version 1



Malte Frövel, Javier Sanmillan, José Maroto, José María Pintado, Iddo Kressel, et al.. Repair Patch Monitoring with Embedded Optical Sensors by the Residual Strain Release. EWSHM - 7th European Workshop on Structural Health Monitoring, IFFSTTAR, Inria, Université de Nantes, Jul 2014, Nantes, France. ⟨hal-01021996⟩



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