Abstract
Abstract
Cracks detection in engineering structures is pivotal for ensuring structural reliability and preventing catastrophic failures. In this article we developed multiplexing capability of reflective matched fiber Bragg Gratings (RM-FBGs) interrogation technique and utilized it for crack detection in an assembly aluminum plates. Firstly, the proposed multiplexing capability is analyzed by applying axial strain on an array of five FBGs pasted on five separate aluminum assemblies. The strain in any FBG due to localized micro-crack resulted in variation its output itself by ascertaining no effect in the outputs of other FBGs, certifying the multiplexing capability of RM-FBGs scheme. The developed RM-FBGs scheme is practically applied micro-cracks detection in a V-shape crack produced in assembly of aluminum plates. The crack is monitored by an array of three multiplexed FBGs epoxied to the plate’s junction at three different positions P1, P2 and P3. Where P1 is at beginning, P2 is at middle and P3 is at end of the crack. Sensitivities of the FBGs at points P1, P2 and P3 were found to be 0.09 ± 0.0001 V μm−1, 0.10 ± 0.007 V μm−1 and 1.08 ± 0.09 V μm−1, respectively and resolutions were found to be 0.22 μm, 0.20 μm and 0.02 μm, respectively. Variation in gauge length of the optical fiber from 100 mm to 200 mm resulted in 76.36% increase in crack width sensing range but at the cost of compromise in sensitivity and resolution. The proposed multiplexed RM-FBG can be deployed for early micro-cracks detection in metallic and non-metallic structures with sub-micrometers resolution.