Assessing the influence of pillar aspect ratio on the behavior of 1-3 connectivity composite transducers

This paper describes a theoretical study, using finite element analysis, into the influence of the ceramic pillar aspect ratio on the behavior of 1-3 connectivity composite transducers. The main objective is to provide working design guidelines for the transducer engineer, with a view toward the cost-effective manufacture of thickness drive and hydrostatic devices. Modal and harmonic analyses are performed to ascertain the conditions under which the composite behaves as a homogenous material, under different values of volume fractions, passive filler material, pillar shape, and distribution. Consequently, a set of criteria is generated to determine analytically the range of aspect ratios for which the composite material behaves homogeneously in the thickness dimension. The influence of polymer loss on these criteria is discussed, along with effects of practical encapsulation and protective layers. Where possible, real data are provided to supplement theoretical predictions, with reasonable correlation between theory and experiment.