Finite element modelling techniques for damping treatments of fuselage panels in composite material

The employment of viscoelastic materials for the passive control of noise and vibration transmitted through panels made of composite material is widely considered as an effective solution in the aerospace field. In the following paper a modelling technique based on the finite elements method able to describe the dynamic properties of a typical fuselage panel is implemented and numerically validated: natural frequencies and damping properties of a panel treated by viscoelastic layer are evaluated. This technique is essentially based on: proper choice of structural elements for the model of panel, proper link of the different elements and a correct description of the boundary conditions. Different models have been developed for a long panel with high width over thickness ratio such to be considered infinite: a 2D model; a 3D model consisting in all brick elements and a 3D model consisting in shell elements for the structural top and bottom plates and in brick elements for the damping layer. In this last case much care has been paid for the description of the boundary conditions. Once validated the technique for infinite panels, a finite element model of a panel supported on the four sides with a damping layer integrated in the mid plane has been developed and the results have been compared with an analytical solution available in literature. The comparison showed a good agreement between the dynamic properties predicted by the technique herein presented and the ones provided by the analytical model and confirmed the care that should be paid for a proper choice of the constraints well representing the structural behaviour of the panel.