Electromechanical response of piezoelectric foams

Abstract A three-dimensional finite element model is developed to completely characterize the elastic, dielectric, and piezoelectric properties of piezoelectric foam structures. Three kinds of 3-3 type piezoelectric foam structures (i.e. with asymmetric interconnects, with symmetric interconnects, and without any interconnects) are identified and their electromechanical properties are characterized as a function of the interconnect geometry and architecture and benchmarked with that of long porous 3-1 type piezoelectric materials over a range of volume fractions/foam densities. In general, at a particular volume fraction a majority of the elasticity constants (with the exception of C 55 and C 13 ) of the 3-3 type open foam structures are lower than that of the 3-1 type long porous structure. Amongst the 3-3 type foam structures the sparsely packed foam structures (with longer and thicker interconnects) display higher coupling constants and acoustic impedance as compared to close-packed foam structures (with shorter and thinner interconnects). The piezoelectric charge coefficients ( d h ), the hydrostatic voltage coefficients ( g h ) and the hydrostatic figures of merit ( d h g h ) are observed to be significantly higher for the 3-3 type (PZT-7A) piezoelectric foam structures as compared with that of the 3-1 type (PZT-7A) long porous materials. For example, at about 3% volume fraction, the d h , g h , and d h g h figures of merit are 360%, 1000% and 5000% higher, respectively, for the interconnect-free foam structure compared with the 3-1 type long porous materials. Amongst the 3-3 type piezoelectric foam structures those that are close packed exhibit higher piezoelectric charge coefficients, while the sparsely packed structures exhibit higher hydrostatic voltage coefficients and hydrostatic figures of merit.