Piezoelectric transducers for actuation control and composite structural health monitoring

Nowadays, many of engineering applications are focused always more in lightweight design for a wide range of components. As consequence, composite materials thanks to their high stiffness to mass ratio, become first choice in setting up new projects. Innovative way to investigate failure mode of structure in composite material has been developed in time. Objective of this thesis is the experimental characterization of piezoelectric transducer as Actuation Control, that is ability to generate deformation as a consequence of a transmitted electrical signal, and Structural Health Monitoring, that is continuous acquisition of data real time/over time in order to detect the presence of fault inside the structure analysed. A number of tests have been executed over a specific piezoelectric patch, isolated and coupled to a host structure, to observe strains generated after signal transmission, both for DC and AC excitation. Moreover, a FEA method is built to model inverse piezoelectric effect, consisting in induction of mechanical strain due to an electrical signal, through a thermal analogy. After that, characterization for acquisition of a signal, transmitted over a structure by a piezoelectric patch and captured by a second one bonded to the same structure, has been accomplished. Contribution about bonding quality, shape wave distortion of imposed signal and best frequency for transmission have been evaluated. Acquired data have been then processed by an algorithm implemented in a Matlab script to obtain detection of defect. Finally, two case studies were designed in order to build up a structural health monitoring system. The first consists of a beam in composite material with two piezoelectric transducers glued over its surface. Signals transmitted by the piezo actuator and received by the piezo sensor are used to detect presence of defect with guided wave method. Successively, six transducers bonded over a plate are used to acquire and process data, with the aim to improve characterization of the fault, adding localization to basic detection. Positive feedbacks and research importance of this advanced technology will be the starting point for next application of a structural health monitoring system over a real industrial component.