DETECTION OF CRACK PROPAGATION IN FOAM CORE SANDWICH STRUCHURES USING FBG SENSORS EMBEDDED IN A CRACK ARRESTER

摘要

A crack arrester has been recently developed to prevent crack propagation along the interface between a facesheet and a core in a foam core sandwich structure. The semi-cylindrical crack arrester inserted in the interface reduced stress concentration at the tip of the crack by sharing the stress due to local deformation around the crack. If the crack propagation can be both inhibited and detected at the same time, reliabilities of the structures will dramatically increase. In this study, the crack propagation was detected by using a fiber Bragg grating (FBG) sensor embedded in the crack arrester. The stress distributed in the crack arrester depending on the crack propagation was evaluated by using a birefringence effect of the FBG sensor. In a double cantilever beam (DCB) specimen, reflection spectra from the FBG sensor split into two peaks due to the birefringence effect when the crack tip reached near the crack arrester. The result was also confirmed by numerical simulation.