Lead zirconate titanate (PZT) fibers are mainly used in active fiber composites (AFC) where they are embedded in a polymer matrix. Interdigitated electrodes (IDE) along the direction of the fibers are used to achieve planar actuation, hereby exploiting the d33 coefficient of PZT. When embedded in the AFC, the PZT fibers are subjected to mechanical loading as well as non-uniform electric field as a result of the IDEs. Therefore, it is important to characterize the electrical and electromechanical behavior of these fibers ex-situ using the IDE electrodes to assess the impact of nonuniform electric field on the properties of the fibers. For that reason, this work aims at quantifying the impact of IDE electrodes on the electrical and electromechanical behavior of PZT fibers, which is necessary for their successful implementation in devices like AFC. The tested fibers were purchased from Advanced Cerametrics and they have an average diameter of 250 micrometers. The IDE electrodes were screen printed on an acrylic substrate. The PZT fibers were subjected to frequency sweeps at low voltages to determine permittivity for parallel and interdigitated electrodes. The piezoelectric e33 constant is determined from electromechanical testing of PZT fibers in parallel electrodes to compare the electromechanical behavior for PZT in bulk and fiber form. The dielectric constant and e33 were found to be lower for the IDE and parallel electrodes compared to bulk but comparable to results published in literature.
Active fiber composites (AFC) are comprised of lead zirconate titanate (PZT) fibers embedded in a polymer. This paper presents an experimental characterization of the PZT fibers and a constitutive model focused on their time-dependent, nonlinear response. The experiments herein focus on characterizing time dependence of various properties by conducting creep, relaxation, mechanical and electric field-cyclic loading at different frequencies. The constitutive model is a time-dependent polarization model that predicts nonlinear polarization and electro-mechanical strain responses of the fibers. The model of PZT fibers is used in the FEM simulation of AFCs and results of the model are compared to experiments for validation.
The mechanical and physical properties of materials change with time which can be due to the viscoelastic effect and/or
due to hostile environmental conditions and electromagnetic fields. An experimental study on active fiber composites
(AFCs) having PZT5A fibers dispersed in epoxy shows that the mechanical response of AFC depends on time,
temperature, and mechanical loading. We examine the time-dependent response of the AFC, where the polymer
constituent undergoes pronounced viscoelastic deformations at different temperatures and mechanical loadings. A
micromechanical model is used for predicting effective time-dependent response in active fiber composites with thermal,
electrical, and mechanical coupling effects. The micromechanical model is derived based on a simplified unit-cell model
in which limited information on the local field variables in the fiber and matrix constituents can be incorporated in
predicting overall performance of active composites. We compare the overall stress relaxation response of the active
composites determined from the micromechanical model with those from available experimental data. We found that the
viscoelastic behavior of the matrix constituent can significantly influence the electro-mechanical coupling response of
the AFC and elevated temperatures accelerate the relaxation process of the epoxy matrix and the AFCs.
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