Vibroacoustic analysis of laminated composite panels stiffened by complex laminated composite stiffeners

This paper investigates the vibroacoustic behavior of stiffened composite panels. Airborne and structure borne excitations are considered. Two models are presented. The first is based on the modal expansion technique and handles both symmetric and asymmetric laminate composite panels and stiffening beams. It uses the first order shear deformation theory for the skin and accounts for the in-plane/bending effects, cross modal coupling and eccentricity of the stiffening beams. The latter are accounted for using equivalent forces and moments and integrated in the skin model using the continuity relations. The second model uses the equivalent properties of the composite panel and beams to extend an existing model, widely used in statistical energy analysis (SEA) of stiffened metallic structures, to composite stiffened structures. Composite panels reinforced by composite stiffeners with three types of cross-sections (I, C and omega) are analyzed. Both irregularly and periodically stiffened panels are studied and compared to the finite element (FEM) for the vibration response and boundary element methods (BEM) for the acoustic response. In FEM simulations, the stiffeners are modeled as surfaces assembly in order to highlight their in-plane displacements and their deformations effects. Excellent agreement with the FEM/BEN analysis is observed in all investigated configurations.