Detection of Debonding Damage in a Composite Plate through Natural Frequency Variations

In the present paper several finite element models suitable for delamina tion damage analysis have been used. Frequency shift diagrams for modes up to 24 with severity of damage up to 15 % have been studied. A correlation between the peaks in the diagrams reporting frequency shifts vs. order of the mode, and the extension of the delami nation is proposed. It is also pointed out the different behaviour of the sensitivities in rela tion with the kind of damage: delamination or thickness reduction. Finally the cross-over phenomenon is shown.