Stiffening effects on the free vibration behavior of composite plates with PZT actuators

The free vibration behavior of thin composite plates with surface bonded piezoelectric patches including stress stiffening effects is investigated. A finite element formulation is presented, based on the Reissner-Mindlin theory and including non-linear strain-displacement relations, to formulate a free vibration eigenvalue problem in the presence of a geometrical stiffness matrix. The case of symmetric laminates and ideal linear behavior is assumed for the piezoelectric actuation. Due to the absence of membrane-bending coupling, in-phase applied voltages produce only inplane-induced piezoelectric stress resultants, which are assumed proportional to the applied voltages. Examples with numerical results for unconstrained plates equipped with piezoelectric actuators show that inplane induced stresses may significantly affect the free vibration behavior. (C) 2000 Elsevier Science Ltd. All rights reserved.