Aluminum Foil Perforation Impact on Acoustic and Thermal Performance of Automotive Sound Absorbers 2019-01-1580

Adding aluminum foil on sound absorber surface has broad application in automotive industry. The foil layer offers thermal insulation for the parts close to exhaust pipes, turbo charge and other heat sources in engine compartment, it also adds physical protection in tough water-splashing/stone-impinging environment at vehicle exterior. It is known that adding impermeable plain foil will impact the sound absorption negatively, so micro perforated aluminum foil is widely used based on micro perforated absorption principle[]. Analytical results of sound absorption from micro-perforated panel or panel with fibrous substrate materials matches very well with measurement when perforation is well controlled in lab environment. However, for industry mass production perforated aluminum foil, it is found that hole size and shape, which are two important parameters of perforation pattern, are not precisely controlled as the samples for lab research, flimsy foil with thickness in between (0.02-0.25mm) is not behaving exactly like elastic panel. In addition, the adhesive film applied on foil back and hot molding process add more uncertainties to part final performance, moreover perforation pattern also might have impact on thermal insulation performance comparing with plain foil. In this paper, experimental acoustic and thermal study was conducted based on samples which have perforated foil from multiple suppliers laminated on typical fiberglass substrate material. The results reveals that there is the best perforation pattern which favors acoustic performance, however foil gage and perforation pattern didn’t make considerable difference in the thermal insulation performance. Instead, it was found that the adhesive to bond scrim and foil has to be carefully selected to avoid part thermal damage. The conclusion from this investigation was used to help foil selection on the development of sound absorbers of automotive vehicles.