Composite Materials Research Progress
Composite Materials Research Progress
Composite Materials Research Progress
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In: <strong>Composite</strong> <strong>Materials</strong> <strong>Research</strong> <strong>Progress</strong><br />
Editor: Lucas P. Durand, pp. 257-273<br />
Chapter 8<br />
ISBN 1-60021-994-2<br />
c○ 2008 Nova Science Publishers, Inc.<br />
ELECTROMECHANICAL FIELD CONCENTRATIONS<br />
AND POLARIZATION SWITCHING BY ELECTRODES<br />
IN PIEZOELECTRIC COMPOSITES<br />
Yasuhide Shindo and Fumio Narita<br />
Department of <strong>Materials</strong> Processing, Graduate School of Engineering,<br />
Tohoku University<br />
Abstract<br />
The electromechanical field concentrations due to electrodes in piezoelectric composites<br />
are investigated through numerical and experimental characterization. This<br />
work consists of two parts. In the first part, a nonlinear finite element analysis is carried<br />
out to discuss the electromechanical fields in rectangular piezoelectric composite<br />
actuators with partial electrodes, by introducing models for polarization switching in<br />
local areas of the field concentrations. Two criteria based on the work done by electromechanical<br />
loads and the internal energy density are used. Strain measurements are<br />
also presented for a four layered piezoelectric actuator, and a comparison of the predictions<br />
with experimental data is conducted. In the second part, the electromechanical<br />
fields in the neighborhood of circular electrodes in piezoelectric disk composites are<br />
reported. Nonlinear disk device behavior induced by localized polarization switching<br />
is discussed.<br />
1. Introduction<br />
Sensor and actuator applications take advantage of the piezoelectric coupling converting<br />
electrical energy into mechanical energy and vice versa. Piezoelectric ceramics and composites<br />
play a significant role as active electronic components in many areas of science and<br />
technology, such as smart and MEMS devices. In some actuator applications, high values<br />
of stress and electric field arise in the neighborhood of an electrode tip in piezoelectric<br />
ceramics [1] and composites [2], and the field concentrations can result in electromechanical<br />
degradation [3, 4]. One of the limitations for practical use of piezoelectric ceramics<br />
and composites is also their nonlinear behavior, which occurs due to polarization switching<br />
and/or domain wall motion at high electromechanical field levels near the electrode<br />
tip. In order to optimize the performance of the piezoelectric devices, it is important to
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