Two-Stage Inverse Method to Detect Delamination in Composite Beam Using Vibration Responses

The present paper deals with a two-stage inverse technique to locate and quantify the delamination damage in composite beams. The first few bending modes are used for damage detection. Initially, the bending mode shapes of the damaged beams are converted to curvature. A gapped smoothing method is applied on the damaged curvature to obtain a damage index, which yields the rough location of the damage along the length of the beam. In the second stage, a unified particle-swarm-optimization-based inverse algorithm is formulated to calculate the size, location, and interface of the damage more accurately by minimizing frequency- and mode-shape-based objective functions. The algorithm detects the single and multiple delaminations accurately, along with the damage interfaces. The results obtained in the experimental investigation of the present method are also mentioned. Overall, the present two-stage method shows good promise in the field of the delamination detection of a composite structure.