Sound absorption mechanism and characteristic of a pressure-resistant sandwich structure supported by carbon fiber truss and embedded cavities in rubber core

This work presents a new underwater pressure-resistant sandwich structure (PRSS) that owns both well mechanical and acoustic properties. The two panels of PRSS are carbon fiber reinforced polymer (CFRP) and the core layer is made of the carbon fiber truss (CFT) and rubber matrix embedded with cavities. The test sample of PRSS is prepared and sound absorption coefficients are measured under various water pressures in the acoustic tube. Meanwhile, the finite element (FE) model of PRSS is established in the COMSOL to simulate its sound propagation behaviors in water. Gained experimental and numerical results have good agreements, which confirm the effectiveness of acoustic tube test and FE simulation. The experiment verifies the efficient sound absorption coefficient (≥0.7) of PRSS at the broadband frequency range (2800 Hz-10000 Hz) and also demonstrates its low sensitivity of sound absorption with respect to the change of pressure (0.1 MPa to 4 MPa). Then the sound absorption mechanism of PRSS is discussed through numerical analyses. It is found that there are two significant absorption peaks in the range of 500 Hz-10000 Hz. Besides, parameters effects on the two absorption peaks are characterized, revealing the critical “acoustic bridge” role of CFT in directing sound energy deeper into the structure and resulting in more dissipation.