Development of a High-Frequency Multilayer Copolymer Acoustic Projector
2006
Kavarnos, George J. | McLaughlin, Elizabeth A.
This report describes the preparation of piezoelectric vinylidene fluoride-trifluoroethylene P(VDF-TrFE) copolymer films for a broadband, high- frequency projector, and the fabrication and acoustic testing of the projector. Raw P(VDF-TrFE) copolymer powder was dissolved in an organic solvent and cast into a shallow mold. After the solvent had evaporated, the -200 microns thick films were annealed and subsequently slow cooled. A gold/palladium metallic layer was sputtered onto both sides of the film for electrodes, and each film was conventionally poled in a hot oil bath. The capacitance of a single layer with an area of 6.45 cM2 (1 in.2) was typically -200 pF. The electroded copolymer layers were bonded together with epoxy and wired in parallel. The piezoelectric constant d33 measured on a four-layer sample, using laser Doppler vibrometry, was -34 pC/N. A seven-layer sample was waterproofed and the projector was evaluated acoustically. The transmitting voltage response at resonance (542 kHz) was 156 dB//microns Pa-m/V, and the bandwidth was 240 kHz.
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