Four-pole modelling of vibration isolators: Application to SEA of aircraft double-wall panels subjected to mechanical excitation

This paper aims at determining the structural coupling loss factor (CLF) between two plates connected via vibration isolators, using a four-pole approach. A hybrid Experimental-SEA (statistical energy analysis) model has been developed for predictions and two configurations are analysed. Configuration 1 is composed of two isotropic plates with critical frequencies around 3750 Hz and 6000 Hz. Configuration 2, more representative of an aircraft fuselage, is composed of a stiffened isotropic plate and a sandwich panel. Plates are coupled at 6 locations via elastomeric mounts. They are mechanically excited by a point force at random positions in the 100 to 10000 Hz frequency range. The modelling of the isolators integrates their frequency dependent measured stiffness. Four configurations are compared for the stiffness measurement and the most adapted setup is derived. The modelled CLFs are then compared with measurements using an experimental SEA approach. Finally, the spaceaveraged quadratic velocities of the plates are calculated using the hybrid model and compared with experiments. Results show a good correlation between predicted and measured CLFs but further refinement is needed in order to account for radiation coupling near the critical frequencies of the plates.