An identification procedure and sensitivity studies on single and multiple delaminations in laminated composite beams are presented. A Spectral Finite Element Model (SEM) based on the Fast Fourier Transform (FFT) is employed. A single damaged spectral element is used to model a uniform composite beam segment with a single delamination, irrespective of its length, by only specifying the delamination location and size. A damage force indicator is used to stimulate the identification procedure. In a realistic identification task, the advantage of the proposed procedure is that only two measurement nodes are sufficient as opposed to several measurement nodes in a standard finite element model with a single delamination. For multiple delaminations, the computation time to perform the identification task shows cubic polynomial complexity and hence is tractable for health monitoring of large skeletal structures. Sensitivity of a damage force indicator with respect to variations in delamination location and size is also presented. The analysis efficiently identifies the severity of delaminated configurations through the damage force indicator. This basic information can be useful in choosing optimal measurement points and the discretized structural model to minimize redundancy in the presence of several other factors such as high noise to signal ratio, damping etc. Conclusions are made on many important issues, which can be addressed with further development based on this preliminary work.
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