Sound Absorption of Polyimide Foams, an Experimental Study

Polyimide foam panels have emerged as advanced solutions in naval, nautical, aeronautical, and railway industries, overcoming limitations associated with the high densities and thicknesses of traditional thermal and acoustic insulation materials. This study aims to experimentally characterize the sound absorption coefficient of both standard and mechanically crushed polyimide foams within the 200-4300 Hz frequency range, utilizing the Standing Wave method with three microphones. Thermally cut samples, designed for thermal insulation, show significant absorption in high-frequency ranges but are less effective at lower frequencies. Remarkably, the mechanical compression of these samples transforms closed pores into open and interconnected structures, substantially enhancing absorption at lower frequencies. This phenomenon is also observed in acoustically cut samples. Polyimide foam shows tuneable sound absorption, with the degree of enhancement dependent on variables such as the number of compression cycles, the applied force magnitude and rotational forces (not evaluated in this paper). Further investigation into these mechanical influences promises insights into optimizing the acoustic performance of polyimide-based solutions.