Investigation of Electromechanical Characteristics of Piezoelectric Unimorph Actuators Under Thermal-Vacuum Conditions Relevant to Low Earth Orbit.

Abstract

Piezoelectric unimorph actuators are promising candidates for precision actuation systems in small satellites, where their electromechanical performance must remain predictable under vacuum and temperature variations. However, actuator performance is determined not only by the piezoelectric material but also by the passive layer and bonding interface, whose combined influence under thermal-vacuum conditions requires systematic evaluation. This study presents a numerical and experimental investigation of the temperature-dependent electromechanical characteristics of piezoelectric unimorph actuators incorporating PIC 181 piezoceramic plates, passive layers made of 7075-T6 aluminum or Ti-6Al-4V titanium, and three different vacuum-compatible bonding materials. Numerical analyses were performed to determine modal, impedance-frequency, and displacement-frequency characteristics over the temperature range of 253.15-323.15 K, while experimental investigations under vacuum conditions quantified the additional influence of the bonding interface. Increasing temperature caused a decrease in resonance frequency for both passive-layer configurations. Actuators with Ti-6Al-4V passive layers generally exhibited higher resonance frequencies, lower impedance values, and larger displacement amplitudes than those with 7075-T6 aluminum passive layers. The maximum measured displacement amplitudes reached 23.11 µm for the aluminum-based actuator and 29.67 µm for the titanium-based actuator at 323.15 K. Among the investigated bonding materials, BM No. 3 consistently provided the lowest impedance and highest displacement response. The results demonstrate that passive-layer and bonding-material selection should be considered jointly and identify the Ti-6Al-4V/BM No. 3 combination as the most favorable among the investigated configurations for resonant piezoelectric unimorph actuation under the tested thermal-vacuum conditions.