Experimental Characterization of Innovative Viscoelastic Foams

Overview & Synopsis

The evolutionary trend in the automotive industry has produced over time numerous performance and aesthetic innovations, however, the exponential development related to transportation technologies also introduced new requirements concerning the environmental impact [1]. The awareness of ecological issues has led to a reorganization of the evaluations and the vehicle design, currently aimed at reducing the problems that have emerged in empirical investigations and the parallel increase in environmental solutions. The vehicle renewal process involves targeted technical mutations both to observance of ecology as to the safety and comfort of the driver. New recyclable materials and more resistant have been developed in order to minimize the environmental impact of the vehicle even at the end of the operating life of its components, as well as solutions relating to the reduction of noise pollution generated as a response to the requirements of comfort. Modern research programs on a global scale have set themselves the objective of exploiting the potentiality of innovative technologies in the optimization of vehicles efficiency, the noise reduction and in the consequent reduction of fuel burn. One of the crucial topics in the greening of the new generation automotive sector is therefore the use and development of high vibro-acoustic performance materials. The goal of this research is properly focused on the analysis of viscoelastic materials appointed to increase the damping of the vibrations generated in a vehicle. The use of a viscoelastic material in this context is due to its high property to convert vibrational energy into heat, providing a significant dissipation of the vibrations. Trade-off analyses are performed in order define the stiffness and damping capacity of several viscoelastic foams with different thickness and density. Introduction. The purpose of the present work is the experimental investigation of new materials and technologies to reduce the noise and vibrations produced inside motor vehicles. It is known, that there are several noise causes of the vehicles, both in the cockpit and in the environment: those of great impact are related to the engine and to the tyre/road interaction processes, that induce noise into the cockpit both through a structure-borne path contribution (mainly the vibration of the car floor induced by the mechanical forcing of the car body floor) and an airborne path contribution. In Figure 1 these noise sources are evident for a moving car. The new low-consumption engines also provide a design, which causes a higher specific noise than the previous ones: new soundproofing solutions are therefore necessary. In this research contest, innovative materials, targeted at the reduction of the car-body floor, will be analysed and compared to " standard one " ; in the specific, viscoelastic foams will be investigated as a valid alternative to conventional add-on damping element as generally used in these applications [2]. The investigation of this class of viscoelastic material in this context is due to the high ability to convert vibration energy into thermal energy, providing a significant increase of vibration damping, hence this aspect will be study in terms of both static and dynamic stiffness and damping factor [3-6].