Vertically Reinforced 1-3 Piezoelectric Composites for Active Damping of Functionally Graded Plates

ONOLITHIC piezoelectric materials (PZTs) have beenwidely used as distributed sensors and actuators fordeveloping smart structures with self-monitoring and self-controlling capabilities [1–10]. However, their major drawback islow control authority as the magnitude of their electromechanicalcoefficientsisverysmall.Thesituationcanbeimprovedbyusinganactive constrained layer damping (ACLD) treatment [11,12] whichconsists of a layer of a viscoelastic material constrained between ahost structure and an active constraining PZT layer. When theconstraining layer is activated with a voltage applied to the PZTlayer, the shearing deformations of the viscoelastic layer areenhanced to improve the damping characteristics of the overallstructures. Since its inception, the ACLD treatment has beenextensively used for efficient and reliable control of flexiblestructures [13–17].Piezoelectric composites, also called piezocomposites, haveemerged as a new class of smart materials and have found wideapplicationsasdistributedactuatorsandsensors.Apiezocomposite,composedofPZTreinforcementsembeddedinaconventionalepoxymatrix, provides a wide range of effective material properties notofferedbyexistingPZTs,isanisotropic,andhasgoodconformabilityand strength. We note that laminae of vertically reinforced 1-3piezocomposites are commercially available [18] and are beingeffectively used as underwater high-frequency transducers and inmedicalimagingapplications[19,20].A1-3piezocompositelaminahas PZT fibers vertically reinforced in the epoxy matrix across thethicknessofthelamina,thefibersarepoledalongtheirlength,andthetop and the bottom surfaces of the lamina are electroded. Theeffective PZT coefficient (e