On the damping coefficient of laminated glass for yacht industry

After a long period in which the most attractive characteristic of a motor yacht was represented by her maximum speed, nowadays the target has moved towards comfort on board which became the fundamental parameter to deal with in the yacht design process. Noise and vibration, together with seakeeping behaviour, became the fundamental subjects on which the research effort of shipyards and technical offices turned on. Since many years the Department of Electrical, Electronic, Telecommunication Engineering and Naval Architecture (DITEN) is involved in a research on the dynamic behaviour prediction of large motor yachts in cooperation with one of the most important Italian shipyards. In this perspective the assessment of the dynamic properties of materials used for the vessel construction, such as the damping coefficient, is an important step to perform preliminary analyses for vibration and noise levels. This paper is focused on the definition of the damping coefficient of laminated glass, which is a complex material commonly used for windows in the current yacht market. As a matter of fact the actual trend of using larger and larger windows for owner's cabins and saloons could represent a critical point in terms of noise and vibrations and makes the laminated glass dynamic characterization a fundamental issue to be investigated. Different experimental modal methods to obtain the damping coefficient at natural frequencies are applied to laminated glass specimens, while the Reverberation Time test is proposed to assess the coefficient in the whole frequency range of interest. In the final part of the paper, a comparison between the results of different methods is presented.