Evaluation of vibro-acoustic behavior of composite fuselage structures realized with embedded viscoelastic damping treatmens

In aerospace field, low structural damping, or high oscillations amplitudes, may impact negatively on structural stability and emitted noise. This is much evident if composite structures are referred to. In force of their stiffness-over-weight ratio, composite materials are deeply used in large assemblies and subassemblies belonging to fuselage and/or lifting surfaces (wing, tail empennages, control surfaces); on the other hand, structural advantages related to composite solutions are accompanied by drawbacks mainly due to materials' high vibration and noise permeability. By increasing structural damping it is possible to obtain a considerable noise and vibration reduction. Composite materials' structural damping can be increased through damping treatments. Among the most common damping treatments in aerospace field, viscoelastic materials embedding is widespread. In order to assess a proper evaluation of their induced damping performances, a rational approach must be defined in order to predict and/or experimentally evaluate damping of deeply heterogeneous layered structural arrangements. Damping of complex structures is often dominated by losses at joints etc. and so is very difficult to be evaluated by means of numerical models. So the damping of treated structures is usually evaluated by experimental tests. Two different coupons were analyzed in this work and the vibro-acoustic behavior was carried out by Impulse Response Decay Method (IRDM). Some tests were performed at different temperature conditions. For each one condition, and for each measurement point, loss factors trends have been evaluated. The effectiveness of the experimental approach has been proved by the mean of a statistical analysis of the obtained results.