Non-linear dynamics of a stiffened composite laminated panel with debonds

Damage or flaws in aeronautical structures compromise performance and safety; therefore, it is very important to identify approaches that can be used for damage detection. In this paper, a composite laminated plate with bonded aluminium stiffeners, which is part of a representative wing structure, is analysed using the finite element method. Debonding is assumed to exist in the connection between the plate and one stiffener, an area found to be critical in previous numerical and experimental static analyses, and several dynamic analyses are carried out. First, it is found that the modes of vibration are only marginally affected by the debonds considered. Then loads that vary harmonically in time are applied to the stiffened panel and contact restrictions between damaged surfaces are imposed. Time histories, phase plane plots, frequency spectra and Poincaré sections of the response in diverse points are extracted. It is verified that these non-linear dynamics based tools allow for the detection of detachments in the connection between stiffeners and composite laminated plates. The response is analysed at several points to see if any are better suited to detect detachment. Different excitation frequencies are attempted and it is shown that excitation at half a resonance frequency has advantages.