Memorization and detection of an arrested crack in foam-core sandwich structures using embedded metal wires and fiber-optic sensors

Abstract

A crack arrester has been recently developed to suppress crack propagation along the interface between the facesheet and the core of foam core sandwich structures. The crack arrester is a semi-cylindrical stiff material inserted into the interface. The crack arrester decreases an energy release rate at the crack tip by suppressing local deformation around the crack. If the arrested crack can be instantaneously detected, damage tolerance of foam core sandwich structures is dramatically improved. This study establishes an innovative crack detection technique using metal wires and fiber Bragg grating (FBG) sensors embedded at both edges of the arrester. Specific strain distribution induced by arresting the interface crack is first memorized by the metal wire and the consequent residual strain is then picked up by the FBG sensor as a damage signal. This study began by simulating sensor response to evaluate the feasibility of the proposed technique. A verification test was then conducted, confirming the spectral change of the FBG can indicate propagation direction and tip location of the arrested crack.