Electromechanical response of piezoelectric foams: Effects of foam shape and porosity aspect ratio

A finite element based three-dimensional numerical model has been developed to completely characterize the elastic, piezoelectric and dielectric properties of 3-3 type piezoelectric foam structures. Upon identifying 15 characteristic foam structures based on foam shape and porosity aspect ratio, the influence of foam shape, porosity aspect ratio, and volume fraction on the effective properties of foam structures is examined. In general, as the material volume fraction increases the elastic, piezoelectric and dielectric properties (with exception of κ ₁₁ for all the structures and κ ₃₃ for some structures) of piezoelectric foam structures increase nonlinearly. Furthermore, the utility of piezoelectric foams for specific applications are assessed by quantifying select figures of merits. Desirable combination of properties (for hydrophone applications) such as low acoustic impedance, high hydrostatic voltage coefficient and high hydrostatic figure of merit is obtained in longitudinally short structures with flat porosity (b=0.25a) and equiaxed foam structures with porosity aspect ratio of 1.