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11 April 2006 Health monitoring of bonded composite repairs using fibre optic sensors
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Structural health monitoring (SHM) technology may be applied to composite bonded repairs to enable the continuous through-life assessment of the repair efficacy. This paper describes an SHM technique for the detection of debonding in composite bonded patches using fibre optic Bragg grating strain sensors. A two sided doubler repair is examined in this paper. A finite element study was conducted which showed that the strain in the debonded region changed significantly compared to the undamaged state. A differential strain approach was used to facilitate the detection of debonds, where two sensors were strategically positioned so that their strain differential increased with the disbond length. With the use of matching gratings, this technique greatly reduces the interrogation equipment requirement by converting spectral information into an intensity-modulated signal, thus allowing a threshold value to be set to indicate imminent critical repair failure. An experimental investigation was conducted, using carbon/epoxy patches to carbon/epoxy substrates, to validate the theoretically predicted results. The experimental measurements agreed well with the numerical findings, indicating that the proposed scheme has great potential as a simple monitoring technique for composite bonded repairs.
© (2006) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Henry C. H. Li, Olivier Dupouy, Israel Herszberg, Paul R. Stoddart, Claire E. Davis, and Adrian P. Mouritz "Health monitoring of bonded composite repairs using fibre optic sensors", Proc. SPIE 6174, Smart Structures and Materials 2006: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, 617418 (11 April 2006);

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