Delamination detection in glass composites using embedded Hi-Bi photonic crystal fiber

In this paper, a novel application of a temperature-insensitive highly birefringent photonic crystal fiber (Hi-Bi PCF) is reported, wherein the Hi-Bi PCF used has been embedded in two glass composite specimens and tested to detect the presence of delamination. The polarimetric–interferometric technique was used to obtain the vibration signature present to allow information on the integrity of the structure to be inferred. The first natural frequencies measured from the specimens with and without delamination (i.e. so-called unhealthy and healthy specimens) have been observed using an embedded Hi-Bi PCF sensor. The reduction in the first natural frequency of the delaminated specimen is used to indicate a reduction in the flexural stiffness of the specimen in comparison to the characteristics of the specimen without delamination. Finally, the performance of the embedded optical fiber sensor has also been compared with that of an accelerometer sensor to enable an evaluation of the optical technique used in this work