Sensitivity analysis for frequency based prediction of crack size in composite plates with through-the-width delamination

This work combines modal analysis measurements with a novel 2D finite element plate model, which is capable to determine the delamination growth based on the change in the measured frequencies. The base of the presented method is a finite element model incorporating the Classical Laminated Plate Theory, and it is capable to estimate the eigenfrequencies of a rectangular plate with through-the-width delamination and straight crack front using arbitrary boundary conditions. The model contains special types of finite elements for modelling the delamination. This results a contact free model, which improves the simulation speed significantly. Using this model, the characteristic of the change of the eigenfrequencies with respect to the delamination growth can be obtained. These results can serve as reference, and according to the theoretical curves, the actual size of the delamination can be estimated based on the change in the measured frequencies. According to our measurement results, it can serve as a good reference for modal analysis. The experiment shows that the model can predict the effect of the delamination growth on the eigenfrequencies very well. Additional conclusions are drawn based on further numerical simulations, which can aid the model based modal analysis of composite plates.