M. C. Ray

Effective Coefficients of Piezoelectric Fiber-Reinforced Composites

The effective coefe cients of piezoelectric e ber-reinforced composites (PFRC) have been determined through micromechanical analyzes. The method of cells (MOC) and the strength of materials (SM) approach have been employed to predict the coefe cients. A constant electric e eld is considered in the direction transverse to the e ber direction and is assumed to be the same both in the e ber and the matrix. MOC and SM predictions for the effective piezoelectric coefe cient of the PFRC assessing the actuating capability in the e ber direction are in excellent agreement. It has been found for the piezoelectric e bers considered that, when the e ber volume fraction exceeds a critical e ber volume fraction, this effective piezoelectric coefe cient becomes signie cantly larger than the corresponding coefe cient of the piezoelectric material of the e ber. The methods also show the excellent matching of the predictions of the effective elastic constants and the dielectric constant of the PFRC in the useful range of e ber volume fraction.

Optimal control of laminated shells using piezoelectric sensor and actuator layers

A simple method for optimal control of vibrations of simply supported thin laminated shells integrated with piezoelectric layers is presented. The piezoelectric layers act as the distributed sensors and actuators. Coupled electromechanical governing equations of motion are derived using Hamiltons variational principle. The algorithm for a linear quadratic regulator with output feedback has been employed to formulate the optimal control problem. Controlled responses for various design parameters are illustrated, and a study of the effect of variation of the central angle subtended by the shell on the performance of the actuator is presented.

The performance of vertically reinforced 1–3 piezoelectric composites in active damping of smart structures

This paper deals with the analysis of vertically reinforced 1–3 piezoelectric composite materials as the material used for the distributed actuator of smart structures. A micromechanics model has been derived to predict the effective elastic and piezoelectric coefficients of these piezoelectric composites which are useful for the analysis of smart beams. In order to investigate the performance of a layer of this 1–3 piezoelectric composite material as the distributed actuator of smart structures, active constrained layer damping (ACLD) of smart laminated composite beams has been studied. The constraining layer in the ACLD treatment has been considered to be made of this piezoelectric composite. A finite element model has been developed to study the dynamics of the overall beam/ACLD system. Both in-plane and out-of-plane actuations of the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. It has been found that these vertically reinforced 1–3 piezoelectric composite materials which are in general being used as distributed sensors can be potentially used as distributed actuators of smart structures.

Optimal control of thin circular cylindrical laminated composite shells using active constrained layer damping treatment

Active control of the vibration of laminated circular cylindrical composite shells has been demonstrated using optimally placed patches of active constrained layer damping (ACLD) treatment. A finite element model has been derived to formulate the dynamics of the composite shells integrated with the patches of ACLD treatment. Optimal placements of the patches are determined by employing a modal controllability criterion to control the first two modes of vibration. The optimal size of the patches located at the optimal places has been determined on the basis of a frequency constraint. The performance of these patches in enhancing the damping of the symmetric cross-ply and angle-ply laminated shells has been illustrated with frequency response functions of the shells.

On the Use of Vertically Reinforced 1-3 Piezoelectric Composites for Hybrid Damping of Laminated Composite Plates

This paper deals with the analysis of vertically reinforced 1-3 piezoelectric composite materials as the material for the distributed actuator of smart laminated composite plates. A simple micromechanics model has been derived to predict the effective elastic and piezoelectric coefficients of these piezoelectric composites which are useful for the three dimensional analysis of smart structures. The main concern of this study is to investigate the performance of a layer of this vertically reinforced 1-3 piezoelectric composite material as the constraining layer of the active constrained layer damping (ACLD) treatment. A finite element model has been developed for analyzing the active constrained layer damping of laminated symmetric and antisymmetric cross-ply and angle-ply composite plates integrated with the patches of such ACLD treatment. Both in-plane and out-of-plane actuation of the constraining layer of the ACLD treatment have been utilized for deriving the finite element model. The analysis revealed that the vertical actuation dominates over the in-plane actuation. Particular emphasis has been placed on investigating the performance of the patches when the orientation angle of the piezoelectric fibers of the constraining layer is varied in the two mutually orthogonal vertical planes. Also, the effect of different boundary conditions on the performance of the patches has been studied. The analysis revealed that the vertically reinforced 1-3 piezoelectric composites which are in general being used for the distributed sensors can be potentially used for the distributed actuators of high performance light-weight smart structures.

Active control of laminated composite beams using a piezoelectric fiber reinforced composite layer

The effectiveness of piezoelectric fiber reinforced composite (PFRC) material in the development of new actuators as elements of smart structures has been theoretically investigated. The piezoelectric fibers considered in this study are longitudinally oriented to yield the bending mode of actuation. Micromechanics is used to predict the effective mechanical properties and the effective electromechanical constant of such composites which gives rise to actuation in the fiber direction when subjected to an electric field transverse to the fiber direction. These effective properties are useful for the analysis of smart beams. A micromechanics study reveals that beyond a critical fiber volume fraction, this electromechanical constant is improved over that of the piezoelectric material alone. The performance of this new material used as distributed actuators has been investigated through active constrained layer damping (ACLD) of laminated composite beams in which the constraining layer is made of piezoelectric fiber reinforced composite. A finite element model has been developed to describe the dynamic behavior of a laminated composite beam coupled with active constrained layer damping (ACLD) treatment. The controlled response is illustrated through plots of frequency response functions. The results indicate that these new piezoelectric composites may be superior candidate materials for use in developing lightweight smart structures, as compared with the existing piezoelectric materials alone.

Finite Element Analysis of Smart Structures Containing Piezoelectric Fiber-Reinforced Composite Actuator

Static analysis of laminated smart composite plates integrated with a piezoelectric fiber-reinforced composite (PFRC) layer acting as distributed actuators has been carried out by a generalized-energy-based finite element model. A simple first-order shear deformation theory is used for deriving the model. Eight noded isoparametric serendipity elements are used for discretizing the domain. The performance of the PFRC layer has been investigated for both symmetric and antisymmetric cross-ply and antisymmetric angle-ply laminated composite shell substrates. The effect of piezoelectric fiber orientation on the control authority of the PFRC layer has also been studied.

Effect of Carbon Nanotube Waviness on the Elastic Properties of the Fuzzy Fiber Reinforced Composites

A fuzzy fiber reinforced composite (FFRC) reinforced with wavy zig-zag single-walled carbon nanotubes (CNTs) and carbon fibers is analyzed in this study. The distinct constructional feature of this composite is that the wavy CNTs are radially grown on the surface of carbon fibers. To study the effect of the waviness of CNTs on the elastic properties of the FFRC, analytical models based on the mechanics of materials (MOM) approach is derived. Effective elastic properties of the FFRC incorporating the wavy CNTs estimated by the MOM approach have been compared with those predicted by the Mori–Tanaka (MT) method. The values of the effective elastic properties of this composite are estimated in the presence of an interphase between the CNT and the polymer matrix which models the nonbonded van dar Waals interaction between the CNT and the polymer matrix. The effect of waviness of CNTs on the effective properties of the FFRC is investigated when the wavy CNTs are coplanar with two mutually orthogonal planes. The results demonstrate that the axial effective elastic properties of the FFRC containing wavy CNTs can be improved over those of the FFRC with straight CNTs.

Zeroth-Order Shear Deformation Theory for Laminated Composite Plates

In this paper a zeroth-order shear deformation theory has been derived for static and dynamic analysis of laminated composite plates. The responses obtained by the theory for symmetric and antisymmetric laminates are compared with the existing solutions. The comparison firmly establishes that this new shear deformation theory can be used for both thick and thin laminated composite plates with high accuracy.

Effective Properties of Carbon Nanotube and Piezoelectric Fiber Reinforced Hybrid Smart Composites

We propose a new hybrid piezoelectric composite comprised of armchair single-walled carbon nanotubes and piezoelectric fibers as reinforcements embedded in a conventional polymer matrix. Effective piezoelectric and elastic properties of this composite have been determined by a micromechanical analysis. Values of the effective piezoelectric coefficient e31 of this composite that accounts for the in-plane actuation and of effective elastic properties are found to be significantly higher than those of the existing 1–3 piezoelectric composites without reinforced with carbon nanotubes.