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The behavior of a cantilever plate instrumented with a piezoelectric sensor and actuator is described using finite-element modeling. To demonstrate the accuracy of the numerical model, a parallel experimental study was carried out in the laboratory for the same geometric dimensions. The two results are compared and show excellent agreement, demonstrating that finite-element modeling is a good approach for optimized smart structure design. A three-dimensional finite-element formulation is employed in the piezoelectric material region and a small neighboring region of the plate structure on which it is mounted. Shell elements, approximated by many flat-shell elements, are used in modeling the remaining part of the plate structure. Transition elements that connect the three-dimensional solid elements to the flat-shell element are used. For the cantilever plate example, the electrical input admittance as well as the sensor response are found from the finite-element analysis and they are compared with experimental measurements. From this, the accuracy and efficiency of this approach is demonstrated. In contrast to many other modeling techniques used for smart structures which are approximate and hence limited, the finite-element model is applicable to complicated geometries.

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An active acoustic coating is presented for layering over objects in a fluid medium. The design of the active coating prevents an incident sound wave from reflecting off the acoustic boundary of a submerged object. The acoustic energy associated with the incident disturbance is absorbed out of the medium through a piezocomposite device in the coating and dissipated by internal electrical means. The components encapsulated inside the elastomer coating are a piezocomposite actuator and piezoelectric polymer sensors. The sensor arrangement detects and separates the acoustic field into a signal in terms of the incident acoustic pressure wave. The signal is manipulated through an electronic network to generate an appropriate driving voltage. This output drives a thickness extensional mode piezocomposite transducer (actuator) with a linear velocity profile over a broad frequency band. The actuator excitation results in a dynamic impedance matching with the incident disturbance such that the coating appears as a nonreflective acoustic surface. An advanced coating design includes an actuator that can be simultaneously driven to reduce the reflected and transmitted sound fields. Experimental results are presented for one-dimensional incident planar acoustic waves propagating in a water filled pulse tube.

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