Implementing optical fibres for the structural health monitoring of composite patch repaired structures

Abstract

Structural health monitoring is increasingly being implemented to improve the level of safety of structures and to reduce inspection and repair costs by allowing for correct planning of these actions, if needed. Composite patch repairing presents an appealing alternative to traditional repair methods as it enables the reduction of closedown time and the mitigation of complications associated with traditional repair methods. As reinforcement with the use of composite patches is predominantly performed at defected structures, the urge to monitor the performance of the repair becomes even greater. This work deals with the use of Fabry Perot optical fibres and strain gages at suitable positions in such a repair. To this end a patch repaired notched steel plate has been tested in tension, opting to gain insight on the mechanisms which govern the failure. In order to investigate how these mechanisms are reflected to the recorded strain measurements, finite element models have been generated. Results indicate that composite patch repairing drastically increased the load bearing capacity of the plates and that optical fibres constitute an appealing health monitoring system for such applications, being able to capture the initiation and evolution of damage.