The application of aliminum foam for the heat and noise reduction in automobiles

Abstract

An experimental study has been conducted to investigate the effective thermal conductivity and sound absorption coefficient of Al and SiCparticle/Al closed-cell foams.The foams were prepared using the foaming of powder compact processes developed by Fraunhofer CMAM. The foaming of powder compact process has been extended for the foaming of composite compacts containing 10 weight percent of SiC particles. Effective thermal conductivity measurements were performed using the temperature distribution for steady state conduction through a uniform plane wall method. The sound absorption coefficient measurements were conducted using the standing wave ratio method. The effect of hole drilling on the sound absorption coefficient of foams was also investigated. The measured effective thermal conductivities of the foams were also fitted to the previously developed effective thermal conductivity models of metal foams.The effective thermal conductivities of studied Al foams were then expressed as function of percent porosity with the best-fitted model equation. The effective thermal conductivity values of Al foams were also compared with those of Alporas closed and ERG open cell foams produced by the foaming of Al melt and investment casting methods, respectively. The sound absorption coefficients of Al and SiC/Al foams were found relatively low and similar at lower relative densities and frequencies. Hole drilling was found to be effective in increasing sound absorption values of foam above400 Hz. The sound absorption in Al and SiC/Al foams was further explained based on the viscous losses and thermal damping effects.