Packaging and Mounting of In-Fibre Bragg Grating Arrays for Structural Health Monitoring of Large Structures

A simple and inexpensive method has been developed for the application and bonding of optical fibre sensor networks to large structures for Structural Health Monitoring applications. The method makes use of a vacuum-assisted infusion technique using a low-cost epoxy resin which was found suitable for surface attachment. Mechanical tests showed no creep of the cured resin, and the response of Bragg grating based sensors was linear up to 5500 mue. There was no hysteresis in the response and the sensitivity displayed at least equals that of a standard electrical resistance gauge. A system for the management and transport of long optical fibres with arrays of sensors was proposed which facilitates safe and easy movement of all sensors from production to application. During application, the same resin infusion technique can be adapted to account for parameters in the size and shape of the structure and the operating environment. A laboratory simulation showed that sensors can be bonded over large distances (10 m) thus making a large-scale, optical fibre sensor network feasible. This work has also revealed a tendency of the fibre to break under load in the splice region where it is connected to the cabled fibre. This is expected as it is the weakest region of the fibre and future work will focus on isolating this region of the packaging from the strain experienced by the structure to which it is bonded.