Improving the Efficiency of Sealing Parts for Hollow Body Network

Nowadays, expanding sealing parts in automotive hollow body networks are widely used. These parts are usually made up from expanding foams or an assembly of expanding foams and solid materials. The use of these sealing parts has demonstrated an influence on the noise inside the car. These findings proved the necessity of designing sealing parts especially to reduce the propagation of sound through the frame cavities and hollow bodies. In this work, experimental investigations have been conducted to characterize the acoustic performances (absorption, transmission loss) of the individual materials constituting the parts and their assembly. Some design rules have been extracted to improve their efficiencies. Also, to better understand the acoustic behavior of the expanding foams, existing theoretical models for closed or open foams have been tested and compared to measurements. The comparisons showed the importance of accounting for the resonant and non-resonant surface absorption of these closed-cell foams. A simplified modeling of the expanding foam consisting of an elastic core surrounded by a resistive layer is proposed and compared to measurements.