Effect of structural damage on modal parameters of a stiffened composite panel using reduced order modelling technique

Abstract

Structural defects have a significant effect on the structural dynamic behavior of a physical system. The dynamic behavior of a multi degree freedom system (MDOF) can be best explained by modal parameter extraction technique. In the present, work the effect of different structural damages on the modal parameters i.e. natural frequencies and modal assurance criteria (MAC) is investigated for a stiffened composite panel using reduced order modeling techniques. In the first phase, a reduced order model of the panel is developed at the location of sensors of the experimental modal testing. After model reduction, model correlation and updating of the reduced order model the panel is performed with the results of experimental modal testing of the panel in cantilever position. Model updating of different parameters like material and geometric properties and stiffness of joints at the fixed end of the panel is performed to match the results of computational modal analysis with experimental modal analysis. After model updating, the reduced order updated FE model is used for evaluation of different damage scenarios (holes, stiffener breakage and internal voids/defects) on the panel and their effect on panel stiffness and mass matrix along with Modal assurance criteria is evaluated. It is concluded that the reduced order FE model can be effectively used for prediction of damage in composite panels under dynamic loading conditions. It is observed that the location and severity of damage can be effectively evaluated by observing the changes in modal parameters of composite panels as these defects have significant effect on natural frequencies, mode shapes and modal assurance criteria (MAC).