Distributed flexoelectric structural sensing: Theory and experiment

“Distributed” sensors are sensitive to spatially distributed structural behaviors, as compared with conventional “discrete” sensors measuring only discrete and local behaviors. The phenomenon of electric polarization induced by strain gradients in solid dielectrics is known as the direct flexoelectric effect. In this study, distributed dynamic sensing using flexoelectric materials is proposed and the flexoelectric signal of distributed flexoelectric sensors laminated on an arbitrary shell structure is defined. Both the open-circuit and the close-circuit models of distributed flexoelectric sensing are developed. An equivalent flexoelectric constant is measured using the proposed open-circuit voltage model. Flexoelectric responses of various locations of a BST beam exhibit consistency and linearity in the case of small deflection. The inferred flexoelectric constant is comparable with the reported maximal coefficient and it also proves that the proposed model is effective to the flexoelectric constant measurement. Distributed sensing behaviors are also experimentally validated on the flexoelectric cantilever beam. Results show that theoretical predictions match well with the experimental results for the fundamental mode. Experiments of distributed sensing signals of beams suggest that distributed flexoelectric sensors are competent to provide the mode shape of strain gradients. Thus, distributed sensing based on the flexoelectric effect is effective to monitoring structural dynamic behaviors.