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24 July 2001 Optical-fiber-based adhesive bondline monitoring system for composite patch systems
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A primary concern with composite repair patches is the potential degradation of load transfer capabilities due to aging and environmental effects. The development of low profile, distributed, embeddable, real-time, optical fiber sensors capable of detecting the onset of patch delamination on repaired regions of the aircraft would eliminate a significant portion of the related maintenance costs as well as improve confidence levels in the technology. The presented sensing system is comprised of optical fiber long period gratings (LPGs) for chemical measurement and Bragg gratings for strain measurement. The sensors can be multiplexed together to monitor the structural health of the patch system and status of any remaining damage in the parent structure. The LPG sensors operate based on specially designed sensing coatings which cause a measurable change in the refractive index 'seen' by the LPG in the presence of target molecules. In this configuration, LPGs can be used to detect moisture infiltration and other chemical changes within a localized environment. Complementary to the long period grating, Bragg grating strain sensors can be fabricated on the same optical fiber to measure load transfer and composite delamination in patches used to repair cracks that occur in aging aircraft.
© (2001) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jennifer L. Elster, Angela Trego, James F. Dante, Mark E. Jones, and Jason Avram "Optical-fiber-based adhesive bondline monitoring system for composite patch systems", Proc. SPIE 4335, Advanced Nondestructive Evaluation for Structural and Biological Health Monitoring, (24 July 2001);

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