Improvements in the Characterization of Viscoelastic Materials for Marine Applications

In recent times, the interest around underwater radiated noise pollution generated by ships and marine vehicles is growing, even in the vision of the compliance of 14th Sustainable Development Goal in United Nations 2030 Agenda, “Life below water”. This, combined with the need of guarantee high comfort levels for passengers and crew, implies actions to increase absorption and dissipation of vibrational energy generated on board. One of the widely adopted solutions consist of viscoelastic materials (VEM) characterized by high levels of damping. In the last times, new strict requirements led to the development of Isocyanate free VEM, so the necessity of a provisional method to investigate in an efficient way new VEM is required. Experimental tests are essential in order to obtain performance indicators (non-standard procedure) or material physical characteristics (Oberst’s beam test, ASTM E756 – 05). In the last times finite element methods (FEM) has been increasingly used. Knowing VEM physics parameters allows numerical simulation in both the provisional and the optimization phase to be accurate and reliable. In this paper, an experimental-numerical small-scale procedure based on the cantilever beam test has been developed and used in order to characterize two different VEM materials, using different specimen thickness. In the proposed method, contrarily from the traditional methods, the loss factor estimation is based on a reverse engineering approach free from peak sharpness dependence. This allows to extend the range of materials that can be analysed, bypassing some typical limitations due to high damping VEMs.