POLYMERIC-COMPOSITE PIEZOFILMS FOR ACTIVE ELEMENTS OF SOUND-TRANSPARENT CONFORMAL SONAR ARRAYS
This paper describes manufacturing technology and main dielectric and electrophysical properties of a new polymeric composite piezomaterial, highlighting its advantages over conventional piezoceramics. The study also suggests a manufacturing technology for active elements of a long conformal emitter/receiver array.Polymeric composite piezomaterial discussed in this paper was based on polyvinyldenfluoride (PVDF) and piezoceramics of lead zirconate-titanate system (CTS). Its main properties given in this study are: frequency curves for dielectric (tangent of dielectric loss angle, relative dielectric constant, quality factor) ane electromechanic (tension piezomodulus, acoustic impedance) properties. Performance parameters of the active element given in this paper are: directional patterns at different frequencies, effective piezomodulus and frequency-piezosensitivity curve.The paper shows that this composite material is equal to conventional PVDF films in terms of its dielectric properties and compliance but offers better electromechanical parameters. Piezoconverter designs suggested in this study feature uniform frequency-sensitivity diagram for both transmission and reception over the whole frequency band under investigation, as well as insensitivityto flow noise. New composite materials newly introduced to hydroacoustics also make these designs of receiving array elements insensitive to parasytic vibration of hull structures.The paper shows the advantages of the developed composite piezofilm as compared to conventional hydroacoustic piezoceramics. Piezofilms, including composite ones, are as sensitive as ceramics but more compact, less heavy and feature much greater specific area ofreception. A promising approach would be to further increase piezomoduli of film-based materials keeping their acoustic impedance low, which would result in greater operational efficiency of receiving sonar arrays.