Abstract
Several previous studies have been dedicated to incorporating double defect modes of a phononic crystal (PnC) into piezoelectric energy harvesting (PEH) systems to broaden the bandwidth. However, these prior studies are limited to examining an identical configuration of the double defects. Therefore, this paper aims to propose a new design concept for PnCs that examines differently configured double defects for broadband elastic wave energy localization and harvesting. For example, a square-pillar-type unit cell is considered and a defect is considered to be a structure where one piezoelectric patch is bonded to a host square lattice in the absence of a pillar. When the double defects introduced in a PnC are sufficiently distant from each other to implement decoupling behaviors, each defect oscillates like a single independent defect. Here, by differentiating the geometric dimensions of two piezoelectric patches, the defects’ dissimilar equivalent inertia and stiffness contribute to individually manipulating defect bands that correspond to each defect. Hence, with adequately designed piezoelectric patches that consider both the piezoelectric effects on shift patterns of defect bands and the characteristics for the output electric power obtained from a single-defect case, we can successfully localize and harvest the elastic wave energy transferred in broadband frequencies.
Highlights
In the last decade, piezoelectric energy harvesting (PEH) that incorporates phononic crystals (PnCs) has drawn growing interest as a breakthrough technology to amplify the amount of input mechanical energy fed into piezoelectric materials [1,2,3,4,5]
With adequately designed piezoelectric patches that consider both the piezoelectric effects on shift patterns of defect bands and the characteristics for the output electric power obtained from a single-defect case, we can successfully localize and harvest the elastic wave energy transferred in broadband frequencies
It is well known that the phononic band gaps (PBGs) represents non-real complex wavevectors [52]; the PnC undergoes exponentially decreasing evanescent waves [53]
Summary
Piezoelectric energy harvesting (PEH) that incorporates phononic crystals (PnCs) has drawn growing interest as a breakthrough technology to amplify the amount of input mechanical energy fed into piezoelectric materials [1,2,3,4,5]. Conventional PEH [10,11,12,13,14] has struggled from the fact that the harvestable electric power is inevitably insufficient when input mechanical energy is small. When a unit cell lies at the scale of the wavelength of the propagating elastic waves, due to destructive interferences resulting from unit cells’ periodicity, Bragg scattering gives rise to the emergence of phononic band gaps (PBGs) in the dispersion curves of the PnC [24,25]. A fascinating phenomenon is observed when a defect, a disordering structure that locally disturbs the periodicity, is deliberately introduced within the PnC
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