Development of a High-Frequency Multilayer Copolymer Acoustic Projector
NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
Pagination or Media Count:
This report describes the preparation of piezoelectric vinylidene fluoride-trifluoroethylene PVDF-TrFE copolymer films for a broadband, high- frequency projector, and the fabrication and acoustic testing of the projector. Raw PVDF-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 goldpalladium 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 pCN. A seven-layer sample was waterproofed and the projector was evaluated acoustically. The transmitting voltage response at resonance 542 kHz was 156 dBmicrons Pa-mV, and the bandwidth was 240 kHz.
- Acoustic Detection and Detectors