A methodology is developed for the development of smart composite patches by embedding Bragg grating optical fiber sensors for the continuous health monitoring of a composite patch repair. It has been established that for composite patch repairs the most critical area is the interface between the aluminium substrate and the composite patch. A series of specimens simulating typical smart composite patch repairs on a cracked aircraft wing skin were manufactured and tested. A manufacturing process was developed by embedding Bragg grating sensors into the composite patch. Artificial debonds were created at the interface between the adhesive and the aluminium substrate and tension tests were carried out. Strains were measured by fiber Bragg grating sensors located between plies 6 and 7 in the boron patch above the crack tip. They were continuously monitored during the test. The specimen was mounted on a tension machine and the Bragg fiber interrogating system was connected to the embedded optical fiber. The specimen was sequentially loaded and unloaded up to 1, 3, 5, 7, 10 kN and strains were recorded. The test was performed under conditions of displacement control. The test results were correlated with reference curves obtained from healthy composite repairs under the same tension loading spectrum. A warning method was established for recording a pre-critical repair condition taking into consideration the critical substrate stress intensity factor and the relevant strain measurements during the debond evolution.
Smart composite patches for repairing aircraft structural components
Smarte Flicken aus Verbundmaterial zur Ausbesserung von tragenden Flugzeugbauteilen
2006
6 Seiten, 10 Quellen
Aufsatz (Konferenz)
Englisch
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