Measurement of surface displacements in 1-3 and 1-1-3 piezocomposites

In a piezoelectric ceramic-polymer composite, the piezoceramic and the nonpiezoelectric polymer will have different deformations when subjected to an external electrical or mechanical stimulus. This local, nonuniform deformation eventually determines the overall electromechanical behavior of the composite. In the current investigation, static surface displacements of piezocomposites with 1-3 and 1-1-3 connectivity were measured using a scanning heterodyne laser interferometer. The influence of a thin interlayer surrounding the piezoceramic rods on the resulting displacement profiles was investigated and correlated with rod/polymer adhesion. The elastic stiffness of the interlayer as well as the interfacial adhesion had a significant effect on the rod displacement. Rods coated with a very compliant interlayer had a much larger displacement than untreated rods, while rods treated with a silane coupling agent to enhance adhesion had a much lower displacement. Experimental displacement profiles were found to be in good agreement with theoretical predictions.