Identification of crack and disbond fronts in repaired aircraft structural panels with bonded FRP composite patches

Structural health monitoring of fatigue-cracked aircraft structural panels repaired with bonded FRP composite patches for extending the service life of aging aircraft has received wide attention. In this paper a method for identifying the locations and shapes of crack and disbond fronts in aircraft structural panels repaired with bonded FRP composite patches is presented. The identification is performed by minimizing the residual norm between the measured in-plane strain range on a strain measurement plane in the FRP composite patches and the calculated in-plane strain range. Several numerical examples of identification of the locations and shapes of crack and disbond fronts are examined. The effects of the number of strain measurement points, position of the strain measurement plane, and measurement errors of the in-plane strain ranges on the identification results are discussed. The validity of this identification method is verified by comparing the identification results with the exact ones.