ANALYSIS ON DYNAMIC ELASTIC MODULUS AND DISSIPATION FACTOR OF POROUS MEDIUM

Open-celled porous medium which has conspicuous damping characteristic is useful to control noise and vibration. This medium is composed of two phases, namely solid matrix and entrapped fluid. The inertia of these two phases and the interaction between them a re taken into account for developing its dynamic el astic modulus and dissipation factor. Simulation shows th at the dynamic elastic modulus is complex number, a nd its real part and image part depend on frequency. F or single-layer open-celled porous medium, the imag e part is not monotonous and reaches peak at a certai n frequency. But the real part increases monotonous ly with frequency. So, its dissipation factor also has one peak at the certain frequency. In low and high frequency ranges, its dissipation factor is very sm all. For two-layer open-celled porous medium, its dissipation factor has two peaks in low and high fr equency ranges, respectively. And, two peak frequencies decrease with the increasing of total thickness of porous medium. In comparison with signal-layer opencelled porous medium, the two-layer one is more ava ilable to control noise and vibration in high frequ ency range.