SUMMARY

Existing research on vibration-based energy harvesting has been mainly focused on the harvesting of deterministic or stochastic vibrational energy. Such an approach is convenient for designing and employing linear and nonlinear vibration-based energy harvesters, such as base-excited cantilevers with piezoelectric laminates. The proposed theoretical and experimental research is centered on the harvesting of structure-borne propagating elastic waves. Specifically, it is aimed to enhance the harvested elastic wave energy by exploiting concepts from metamaterials as well as nonlinear dynamics. In the first part of this research, the focus is placed on a one-dimensional beam configuration for piezoelectric energy harvesting from bending waves through optimal resistive-reactive electrical loading, spatially localized obstacle for harvesting local reflections, and a multifunctional energy-harvesting electromechanical non-reflective boundary condition. Having validated the distributed-parameter electroelastic model, the scenario of periodic piezoelectric energy harvesters is explored with an emphasis on bandgap and power flow behaviors. Secondly, in the one-dimensional wave energy harvesting problem, frequency bandwidth enhancement through a bistable energy-harvesting inclusion is considered and the overall electromechanical performance is explored by studying the amplitude-dependent reflection, transmission, and energy harvesting characteristics associated with intrawell quasilinear, intrawell nonlinear, and interwell nonlinear oscillations of the bistable electroelastic component. Finally, two-dimensional wave energy harvesting concepts are explored with an emphasis on wave focusing in plates. Gradient-Index Phononic Crystal Lens (GRIN-PCL) is fabricated for the harvesting of elastic plane waves that are in the form of the lowest asymmetric Lamb wave mode. The GRIN-PCL structure is an array of blind holes with different diameters in an aluminum plate domain where the orientation and size of the blind holes are based on a hyperbolic secant gradient distribution. As a second part of the focused wave energy harvesting efforts, a Luneburg lens setup is also fabricated and tested in an effort to alleviate directivity issues in energy harvesting. Overall the proposed research aims to provide electroelastic models and novel approaches to efficient and broadband elastic wave energy harvesting in one-dimensional and two-dimensional structures.