Effects of Structural and Electrical Defects on Vibration Suppression and Energy Harvesting Performance of Piezoelectric Metamaterial Beam

This paper investigates the vibration suppression and energy harvesting performance of a locally resonant piezoelectric metamaterial beam (PMMB) with structural and electrical defects. The unit cell of a PMMB comprises a square aluminum substrate, two rubber plates sandwiching a piezoelectric plate, and a cylindrical stub on top. The structural and electrical defects are introduced by varying the material density of a stub, adjusting the spacing between the two adjacent piezoelectric local resonators (PLRs), and connecting inductors to selected PLRs, respectively. To investigate the theoretical band gap (BG), the effective BG (i.e., attenuation band), and the energy harvesting performance of defect-configured PMMB, supercell finite element were performed to obtain dispersion curves, while the six-PLR PMMB simulations were conducted to acquire transmission spectra and responding voltage outputs. Three distinct mechanisms are explored to enhance the performance of PMMB: defect states inside the effective BG for energy localization, defect–boundary interference for energy redistribution in the passband, and LC resonance in the shunted piezoelectric resonators for frequency-tunable energy harvesting. The results demonstrate that either stub-mass-reduced defect or substrate-length-increased spacing defect yield high voltages via energy localization in the effective BG, but they also narrow the effective BG. In contrast, tuning the center-to-center spacing of the two adjacent PLRs (near the excitation end) to an appropriate distance generates a dominant passband peak. The significant rises in both the far-end PLR voltage and the total voltage of the six PLRs clearly indicate energy redistribution within the passband. By selecting appropriate inductor parameters, LC-resonance-based electrical defects enable frequency-tunable voltage enhancement either at the effective BG edge or within the passband. Overall, this study provides comprehensive insight into how structural and electrical defects affect the response characteristics of the locally resonant PMMB.