Homogenization of PMN-PT/epoxy 1-3 piezocomposites by resonator measurements and finite element analysis

The objective of this work is to derive the full material constants of an equivalent single phase material to replace the complex-structured PMN-28%PT (lead magnesium niobate-28%lead titanate)/epoxy 1-3 composite in finite element analysis (FEA) of acoustic transducers. No attempts have been made to derive full material constants of the homogenized PMN-PT/epoxy piezocomposites. In this study, the equivalent properties were derived by extensive resonance analyses and the FEM. The PMN-28%PT crystals have tetragonal 4 mm symmetry and thus have eleven independent material constants in total. FE models of piezocomposite resonators of six different configurations were constructed to analyze all possible vibration modes of the composite. All the material constants of the equivalent single phase material were extracted from the simulation data with the FE models so that the equivalent material can have identical resonant characteristics as the full complex-structured PMN-PT/epoxy composite. The validity of the homogenization technique and the accuracy of the equivalent material constants were verified by comparing the impedance spectra of the single phase resonators with those of the full-structured piezocomposite resonators. The accuracy and efficacy of the homogenized material constants was verified further by comparing the performance of multi-layered hydrophones made of the full-structured 1-3 piezocomposite as well as the equivalent single phase material. The homogenization procedure can be applied to 1-3 piezocomposites with an arbitrary volume fraction of the PMN-PT single crystal.