Optimized design of auxetic substrates for enhanced electric power output in piezoelectric composites

Auxetics, characterized by their unique deformation behavior, possess the potential to improve the electric power output of piezoelectric composites utilized in energy harvesting applications. This study investigates the effects of different two-dimensional auxetic substrates on piezoelectric composites and assesses the suitable environments for each type of auxetic piezoelectric composite. Additionally, this research proposes a three-dimensional auxetic substrate with the characteristics of compression-torsion coupling structures. This innovative three-dimensional auxetic substrate not only retains the advantages of two-dimensional auxetic substrates, but also enables the piezoelectric composites to engage both the 31, 32 and 33 modes of piezoelectric materials in the d₃₃ operating mode for electric power generation. The performance of three-dimensional auxetic piezoelectric composites is evaluated using finite element (FE) modelling, with the findings validated through experiments. Experimental results demonstrate that the output voltage and power generated by three-dimensional auxetic piezoelectric composites can reach 4.99 times and 24.92 times, respectively, that of ordinary piezoelectric composites in the d₃₃ operating mode. This study further corroborates the advantages of employing auxetic substrates in piezoelectric composites and provides significant insights for future research endeavors.