An experimental study to improve the performance of unimorph piezoelectric actuators subjected to external loading

This paper presents an experimental study to investigate the actuation performance of LIPCA (Lightweight Piezo-Composite unimorph Actuator) with different loading cases. High value of the manufacturing-induced compressive stress in PZT layer of LIPCA helps avoiding potential in-service failure, however, it may cause a reduction in strain due to the induced piezoelectric effect. High compressive prestress makes the domains aligned and constrained perpendicular to the stress direction. Consequently, fewer domains can be reoriented to contribute to polarization and strain output. The unimorph actuator is thus designed and operated such that the compressive stress in piezoceramic material is large enough to avoid failure in working condition but small enough to allow larger amount of non-180 degrees domain switching. To compensate the high designed compressive stress state in the piezocerarnic attention should be paid on the loading configuration when the actuator is working in-service condition. Experimental results show that the actuator should be arranged in a manner such that the stress state within the PZT wafer is in as more tension as possible to compensate the high compressive induced stress in the piezoceramic due to the manufacturing process.