Fatigue crack growth monitoring by optical fiber sensors in smart composite patch repairs

Abstract

The fiber optic smart structures allow engineers to add nerve systems to their designs, giving structures capabilities that would be very difficult to achieve by other means, including continuous assessment of damage processes. In this study, we evaluated the potentiality of the application of the optical fiber sensors to the monitoring of the fatigue crack growth behavior of composite patch repaired structures. The composite patch with embedded optical fiber sensors can be considered as a smart patch which has both repairing and monitoring functions. We used recently developed Transmission-type Extrinsic Fabry-Perot Interferometric (TEFPI) optical fiber sensors for the monitoring of fatigue crack growth behavior of cracked thick aluminum plate repaired with bonded composite patch. The sensing principle and the senor construction of the optical fiber sensor are presented. The experimental results show that it is possible to monitor the fatigue crack growth behavior of structures repaired with composite patch using the optical fiber sensors.