Composite Materials Research Progress

266 Yasuhide Shindo and Fumio Narita
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Figure 6. Displacement versus voltage for laminated actuator.
Next, the effect of electrode length on the performance of the actuator with L = 30 mm,
W = 10 mm and 4h = 20 mm is discussed. Fig. 6 shows the predictions of displacement
uz at x =0mm, y =0mm and z =10mm as a function of applied voltage V0, based on
work, for a =20, 24 and 28 mm. Non-linearity in the displacement versus voltage curves
depends on the electrode length. The displacement increases with an increase of a from 20
mm to 24 mm. Little difference is observed between the results for a =24mm and 28 mm.
4. Piezoelectric Disk Composites
4.1. Problem Statement and Solution Procedure
Consider a two-layered piezoelectric disk composite with radius c and thickness h as shown
in Fig. 7. The origin of the coordinates (r,θ,z) is located at the center of the interface
considered as z =0, 0 ≤ r ≤ c. The z axis is assumed to coincide with the six fold
axis of symmetry in the class of a 6mm crystal class, or with the poling axis in the case
of poled piezoelectric ceramics. Three parallel circular electrodes of radius b lie in the
planes z =0, ±h. The bonding at z =0is assumed to be perfect so that the stresses and
displacements are continuous along the interface of the composite. Let the voltage applied
to the internal electrode surface be denoted by V0. The surface electrodes are grounded.
The axisymmetric models were generated using the commercial FE method software
package. The electrode layers were not incorporated into the model.