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Matteo Carrara
Georgia Institute of Technology
School of Aerospace Engineering
Frequency-wavenumber Design of Spiral
Macro Fiber Composite Directional
Actuators
This work is focused on design and testing of a novel class of transducers for Structural Health Monitoring (SHM),
able to perform directional interrogation of plate-like structures. These transducers leverage guided waves (GWs),
and in particular Lamb waves, that have emerged as a very prominent option for assessing the state of a structure
during operation. GW-SHM approaches greatly benefit from the use of transducers with controllable directional
characteristics, so that selective scanning of a surface can be performed to locate damage, impacts, or cracks. In the
concepts that we propose, continuous beam steering and directional actuation are achieved through proper selection
of the excitation frequency. The design procedure takes advantage of the wavenumber representation of the device,
and formulates the problem using a Fourier-based approach. The active layer of the transducer is made of
piezoelectric fibers embedded into an epoxy matrix, allowing the device to be flexible, and thus suitable for
application on non–flat surfaces. Proper shaping of the electrodes pattern through a compensation function allows
taking into account the anisotropy level introduced by the active layer. The resulting spiral frequency steerable
acoustic actuator is a configuration that features (i) enhanced performance, (ii) reduced complexity, and (iii) reduced
hardware requirements of such devices.