Multi-layer piezoelectric PVDF transducers for nondestructive testing of concrete structures

Abstract

Polyvinylidene fluoride (PVDF) and its copolymer (PVDF-TrFE) are known to yield lower electromechanical coupling than ceramic transducers. It is possible to increase transducer efficiency by using two or more PVDF layers with embedded electrodes by configuring the transducer layers in different ways such as folded, barker coded and switchable barker coded [Zhang et al., 1997]. A multi-layer transducer can be designed in a configuration that can be electrically shielded to reduce capacitive induced currents. In this work we evaluated and compared ultrasonic field generated by single and multi-layer transducers of PVDF. The multi-layer transducers are then used to analyse the defects on the concrete structures.