Fibre optic sensors for delamination identification in composite beams using a genetic algorithm

Fibre Bragg grating (FBG) sensors associated with a genetic algorithm (GA) were used to detect and identify the size and location of delaminations in composite beams. A theoretical beam model is implemented into the GA for on-line delamination parameter searching. The objective function of this vibration-based delamination detection problem in the GA is defined as the sum of squared ratios of the differences between the shifts of eigenvalues of a delaminated beam measured by the FBG sensors and calculated from the theoretical beam model to the eigenvalues of an intact beam measured by the FBG sensors in the first three vibration modes. The principle of the FBG sensors for vibration detection is briefly discussed in this paper. A laser vibrometer and an accelerometer are utilized to compare the results measured from the FBG sensors. The reliability of using the FBG sensors for delamination detection is highlighted. Different delamination sizes and locations in spanwise and thickness-wise directions of the beams are simulated to demonstrate the feasibility of using the GA for the detection of delamination in the composite beams.