Low-temperature Lamb wave propagation in PVF2

Abstract

Lamb wave propagation in thin films of polyvinylidene fluoride PVF₂ is examined as a function of temperature. Results are presented for frequencies from 10 to 70 MHz and temperatures from −50 to −175 °C. Lamb waves were excited in the 28.4‐μm‐thick films by interdigital transducers with a center frequency wavelength of 92 μm. At the fundamental wavelength, the first five Lamb modes were observed, while at the third harmonic of the transducer only the first two branches of the dispersion curves could be detected. The observed velocities of the seven modes are compared to the theoretical dispersion curves to obtain stiffness constants for the PVF₂ film as a function of temperature. The results obtained for constants c₃₃ and c₅₅ are in agreement with previous literature. Values for the constants c₁₁ and c₁₃ are presented for the first time.