Structure Research of Resistance Shunt Type Piezoelectric Composite and Underwater Sound Absorption Performance Analysis

The high-efficiency sound absorption of underwater sound-absorbing materials under "low frequency" and "wide frequency" conditions has become a hot topic in current research. Underwater semi-active sound absorption can help to improve low frequency sound absorption performance by designing the structure of the piezoelectric composite and the shunt circuits, and it is also advantageous due to its simplicity, compactness, ease of installation, low cost, and high stability. In this paper, a kind of resistance shunt type piezoelectric composite is designed, and its underwater sound absorption performance is analyzed. Theoretical analytical formulas and finite element numerical calculation are used to calculate the electro-elastic constants of the piezoelectric composite. The theoretical model based on the Mason equivalent circuit and transfer matrix theory is used to calculate the sound absorption coefficient. Through the study of 0-3 and 1-3 composites used in the existing research work, it was found that the piezoelectric composite which is suitable for resistance shunt type underwater semi-active sound absorption should have a low longitudinal wave velocity and high electromechanical conversion coefficient. According to this design objective, the structure of the piezoelectric composite has been gradually modified, and finally it is determined that the sparse oblique 2-1-3 composite is an appropriate type of piezoelectric composite. Theoretical calculations and simulation experimental measurement verifies that when the inclination angle is 21 deg and the shunt resistance is 10 kOhm or the inclination angle is 24 deg and the shunt resistance is 10 kOhm, the sound absorption coefficient within the low frequency band 1--3~kHz can be significantly improved.