The Effect of Processing Parameters on the Acoustical Efficiency of Open-Cell PMMA Materials 2006-01-0711
Porous materials are widely used for noise control in the automotive industry. However, due to the weight and space saving considerations, the use of bulky thicknesses of these materials is limited in industrial applications, thus reducing the effectiveness of the acoustic treatment. Consequently, thinner materials with improved acoustic properties are required to achieve a satisfactory noise reduction. One of the promising methods to enhance the acoustic performance of a porous material is the optimization of its macroscopic acoustic parameters through inner micro-structure properties control. Thematically, it is of interest to understand and link material inner micro-structure such as cell size, cell distribution, etc. to main macroscopic parameters which control the sound absorption of a material such as porosity, flow resistance, etc. This study presents a new processing technology to manufacture open-cell PMMA materials using a gas foaming/particulate leaching method and a constrained foam molding process. A parametric study is conducted by altering the processing parameters such as foaming temperature, size and percentage of foaming agent which affect the cell morphologies and control the macroscopic properties. The acoustic performance is controlled by adjusting the processing parameters with respect to the inner structure of the material. The correlations between the resulting cell morphologies and sound absorption effectiveness are investigated. The results conclude that understanding and controlling the porous material inner structure through adjusting the processing parameters are crucial for the development of porous materials with optimized acoustical efficiency.