Durability of Co-bonded Piezoelectric Transducers

The Structural Health Monitoring (SHM) technique Acousto Ultrasonics is based on a permanently installed piezoelectric transducer network. A reliable and effective transducer installation procedure shall be developed so that SHM represents a feasible alternative to the currently used Non-Destructive Testing (NDT) in Aircraft. A co-bonding procedure has been considered for transducer installation as a time and cost efficient method, while arising additional requirements regarding the transducer properties and the manufacturing processes.This paper focuses on the mechanical durability of DuraAct™ piezoelectric patch transducers, which have been co-bonded on Carbon-Fiber Reinforced Polymer (CFRP) plates. The samples were tested in quasi-static and cyclic loading conditions at different loading levels. The degradation of the DuraAct™ piezoelectric transducers is assessed by means of three monitoring methods: The electro-mechanical impedance spectrum, the charge issued from the direct piezoelectric effect when the piezoelectric transducers undergo mechanical deformation and the guided ultrasonic waves sent and received by the transducers.