Trim and floor influence on vibrational response of an aircraft fuselage model

The influence of the interior trim and the door partition on the vibratory response of the physical model of an aircraft fuselage model was investigat ed experimentally. The one-third scale model faithfully replicated the sali ent structural features of a rear-engine aircraft fuselage. Detailed modal analysis of the green fuselage, i.e., the bare fuselage skin without any fl oor, trim, or lining, was first performed. The effects of adding a honeycom b floor partition, a sound-absorbing blanket, and a thin plastic interior l ining on the modal parameters of the structure were then determined. It was found that the addition of the sound-absorbing blanket significantly incre ased the structure's modal damping coefficients for its first five modes of resonance. Notable changes in the structural response at higher frequencie s were also observed. These results strongly suggest, in agreement with rec ent studies reported in the literature, that sound-absorbing blankets do ad d significant damping to the vibration response of the structure (in additi on to absorbing sound energy from the cabin interior). These damping proper ties may be used advantageously for the optimal design of skin-damping airc raft noise-control treatments for minimal added weight, and minimal cost.