Investigation on microperforated sandwich structures with light weight and broadband sound absorption: Influences of foam filling and core configurations

Structures with light weight and broadband sound absorption is of vital importance for noise control applications in engineering practice. Foams exhibit broadband but poor low frequency sound absorption, micro-perforated sandwich structures conversely possess good sound absorption at low frequencies due to resonance, the bandwidth is however limited. Micro-perforated sandwich structures with foam filling are therefore proposed in the paper to obtain wideband low-frequency sound absorption. An integrated analytical, numerical and experimental research is conducted to investigate sound absorption and lightweight characteristics of four commonly used micro-perforated sandwich structures with honeycomb (PHSP), corrugated (PCSP), N hybrid (PNHSP) and honeycomb-corrugated (PHCSP) cores. An analytical model is built to estimate sound absorption coefficient (SAC) based on the acoustic impedance theory and Johnson-Champoux-Allard model. Numerical simulation and experimental measurement methods are conducted simultaneously to validate the analytical model. The influences and underling mechanism of foam filling and filling configurations are explored, and it is found that melamine foam filling can enhance low-frequency sound absorption bandwidth of micro-perforated sandwich structures, and half-filled foam can bring in higher absorption peak values than fully filled foam due to more violent resonance. To overall evaluate both the lightweight and sound absorption performance of varied sandwich cores, a comprehensive evaluation index by the sound absorption and relative mass is developed. Results show that the PCSPs with lower half part filled foam perform best at both sound absorption and lightweight among all sandwich structures. Results of this paper can provide guidance for the application of sandwich structures.