Optimum design of laminated composite plates under dynamic excitation

An integrated model for optimum weight design of symmetrically laminated composite plates subjected to dynamic excitation is presented in this work. Optimum design procedure based on flexibility and strength criteria is presented. The objective is to determine the optimum thicknesses of the laminate layers and its optimum orientations without exhibiting any failure according to Tsai-Wu failure criterion. The finite element method, based on Mindlin plate theory, is used in conjunction with an optimization method in order to determine the optimum design. Newmark algorithm, as an implicit time integration scheme, is used to discretize the time domain and calculate the transient response of the laminated composite plate. Exterior penalty method is exploited for the constrained minimization procedure. Fletcher-Powell algorithm is used for the unconstrained minimization process. To verify the capability and efficiency of the proposed model, three examples are solved. The examples deal with flexibility and stress constraints for different boundary conditions under various dynamic excitations.     

On the Cauchy problem for thermoelastic plates

The Cauchy problem for an infinite thermoelastic plate with a non‐homogeneous governing system and homogeneous initial conditions is solved by means of an area potential. This is the first step in the construction of a potential theory for time‐dependent problems for thermoelastic plates, enabling the reduction of various initial‐boundary value problems to their versions for the homogeneous system of equations with homogeneous initial conditions, which, in turn, may then be solved by means of dynamic potentials. Copyright © 2006 John Wiley & Sons, Ltd.     

Nonlinear dynamic response of laminated composite plates subjected to pulse loading

An analytical solution methodology for the non-linear dynamic displacement response of laminated composite plates subjected to different types of pulse loading is presented. The mathematical formulation is based on third-order shear deformation plate theory and von-Karman non-linear kinematics. Fast-converging finite double Chebyshev series is employed for evaluating the displacement response. Houbolt time marching scheme is used for temporal discretization and quadratic extrapolation technique is used for linearization. The effects of magnitude and duration of the pulse load, boundary conditions and plate parameters on the central displacement and bending moment responses are studied.     

Analysis of laminated piezoelectric composite plates using an inverse hyperbolic coupled plate theory

This paper presents a non-polynomial coupled plate theory for smart composite structures employing inverse hyperbolic displacement and electric potential functions. The theory is utilized towards analysis of composite piezoelectric plates operating in sensor and actuator modes. Particularly, the following three cases are studied: (i) passive laminated composite structure, (ii) composite piezoelectric plate actuator and (iii) unimorph and bimorph piezoelectric plate sensors. Analytical solutions are obtained for simply supported plates under static electrical and mechanical loads. These results are validated with existing 3D elasticity solutions and compared with other plate theory solutions. Furthermore, parametric studies are performed to determine the effect of loading, span-to-thickness ratio and lamination sequence on the response of the piezoelectric plate. Finally, the theory is applied to a transverse shear sensing device which utilizes transverse shear-electric field coupling in piezoelectric materials. This effect is often ignored in literature.It is observed that the maximum percentage error of the present theory, when compared with 3D results, is less than 3%, which is lower than other higher order plate theories.     

A vibration analysis of composite laminated plates

A finite element formulation of the equations governing laminated anisotropic plates using Reddy's higher-order theory is presented. This simple higher-order shear deformable theory takes into account the parabolic distribution of the transverse shear deformation through the thickness of the plate and contains the same unknowns as in the first-order shear deformation theory. Finite element solutions are presented for rectangular plates of different layups, such as cross-ply, antisymmetric angle-ply, and sandwich plates with various material properties, boundaries, and plate aspect ratios. The numerical results are compared with the available closed-form results, the 3-D linear elasticity theory results, and the other available numerical results. A comparison is also made with test data from a laminated cantilever plate.     

A nonlinear mixture theory for the dynamic response of a laminated composite under large deformations

A nonlinear mixture theory of solids is derived to model the dynamic response of a laminated medium under large deformations. The composite is made of constituents which obey a nonlinearly elastic constitutive law. The microstructure effects are taken into account in this mixture model in which every constituent has its own motion but is allowed to interact with the other. The model is developed by applying an asymptotic expansion, which by a proper truncation can be cast into nonlinear binary mixture equations. Linearization of the equations for the case of infinitesimal deformations yields the linear mixture model developed previously. The model is applied to a laminated slab under time dependent loading and results are given for both positive and negative loadings and contrasted with the corresponding linear responses.

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Zusammenfassung Eine nicht-lineare Mischungs-Theorie für Festkörper wird abgeleitet als Modell für das dynamische Verhalten von laminierten Verbund-Medien bei grossen Verformungen. Die Bestandteile im Verbund gehorchen nicht-linearen elastischen Grundgleichungen. Die Mikrostruktur wird berücksichtigt in diesem Mischungs-Modell, in dem jeder Bestandteil seine eigene Bewegung hat, aber die gegenseitige Beeinflussung wird berücksichtigt. Das Modell wird aufgestellt mit der Benützung einer asymptotischen Entwicklung, die so abgebrochen wird, dass die Gleichungen für nicht-lineare binäre Mischungen entstehen. Linearisierung ergibt die Gleichungen für das lineare Mischungs-Modell, die schon früher abgeleitet wurden. Das Modell wird angewendet für den Fall eines laminierten Balkens unter zeitabhängiger Belastung; Ergebnisse werden für positive und negative Lasten gegeben, und mit den linearen Lösungen verglichen.

     

The traction initial-boundary value problem for bending of thermoelastic plates with cracks

The initial-boundary value problem for bending of a thermoelastic plate weakened by a crack, with Neumann-type boundary conditions along the edges of the crack, is studied, and its unique solvability in spaces of distributions is proved by means of a combination of the Laplace transformation and variational methods.     

Two new hyperbolic shear displacement models for orthotropic laminated composite plates

Two hyperbolic displacement models, HPSDT1 and HPSDT2, are developed for a bending analysis of orthotropic laminated composite plates. These models take into account the parabolic distribution of transverse shear stresses and satisfy the condition of zero shear stresses on the top and bottom surfaces of the plates. The accuracy of the analysis presented is demonstrated by comparing the results with solutions derived from other higher-order models and with data found in the literature. It is established that the HPSDT1 model is more accurate than some theories of laminates developed previously, and therefore the analysis can be expanded to laminated composite shells.     

A method of solving three-dimensional problems of elasticity for laminated composite plates

An efficient method of solving 3D elasticity problems for thick and thin laminated composite plates is presented. It is based on a new concept of reference surfaces inside the plate. According to this concept, into each nth layer, In arbitrary reference surfaces parallel to the midsurface are introduced, and the displacement vectors of these surfaces are chosen as unknown functions. Such a choice allows one to represent the governing equations of the high-order theory of plates proposed in a very compact form and to derive strain–displacement relationships correctly describing all rigid-body motions of laminated plates.     

On the theory of thermoelastic bending of reinforced shells and plates

The author examines an approach to the construction of a theory of thermoelastic bending of arbitrarily reinforced shells and plates that takes into account the actual structure, the deformation characteristic, and the actual thermomechanical properties of the elements which make up the composite. The final equations are obtained with and without allowance for transverse shear strains. The problem of the thermoelastic bending of a thin, arbitrarily reinforced rectangular plate hinged at the edges, when transverse shear strains can be neglected, is considered as an example.Institute of Hydrodynamics, Siberian Division, Academy of Sciences of the USSR, Novosibirsk. Translated from Mekhanika Polimerov, No. 5, pp. 861–873, September–October, 1972.     

Unilateral dynamic contact problem for viscoelastic Reissner-Mindlin plates

The existence of solutions is proved for systems of dynamic Reissner-Mindlin equations expressing vibrations of viscoelastic plates. We consider the cases of short memory and singular memory material. Contact with the rigid support is considered.     

Fundamental solution of a plane problem of elasticity theory for a composite anisotropic medium

The plane problem on the action of an arbitrarily oriented concentrated force, applied at some point of an elastic plane, composed of two different anisotropic half-planes, is considered. By a special choice of a particular solution the problem reduces to a well-known differential equation of the anisotropic theory of elasticity with discontinuous coefficients. The latter reduces, by the method of the integral Fourier transform, to the Riemann boundary value problem. Expressions for the stresses and displacement derivatives at an arbitrary point of the plane are obtained. The application of the obtained results is illustrated on the example of a problem on an elastic linear inclusion (strap).Translated from Dinamicheskie Sistemy, No. 4, pp. 40–45, 1985.     

A dynamic theory for composite materials

A continuum model is developed for a composite medium consisting of inclusions of arbitrary geometry embedded in a matrix material. The equations are valid up to wave lengths of the order of a unit cell dimension and are found to reduce under special assumptions to Mindlin's equations in the long wave-length approximation. In particular, a pair of characteristic time scales and length scales encountered in stress-gradient theories are evaluated in terms of known constituent material properties. As a basis of the theory, it is shown that adefinite relation exists between the dimensions of a local representative volume and those of a unit cell. The relation is found to depend on the ratio of the maximum and minimum effective elastic impedances. As a consequence, the theory hinges on the evaluation of several material constants that reflect the effect of inclusion arrangement in a local representative volume of definite dimensions.

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Zusammenfassung Ein Kontinuumsmodell für ein Verbundmaterial mit Einschliessungen willkürlicher Geometrie wird vorgeschlagen. Die Gleichungen sind bis zu Wellenlängen von der Grössenordnung der Dimension einer einheitszelle gültig. Sie reduzieren sich unter speziellen Annahmen zu den Mindlinschen Gleichungen in der Approximation für grosse Wellenlängen. Insbesondere können die in Theorien mit Spannungsgradienten auftretenden charakteristischen Zeit- und Längenmasstäbe in Funktion von bekannten Materialeigenschaften berechnet werden Als Grundlage der Theorie ergibt sich, dass zwischen den Dimensionen eines lokalen, representativen Volumens und jenen einer Einheitszelle eine wohldefinierte Beziehung besteht. Diese hängt vom Verhältnis der maximalen und minimalen elastischen Ersatzimpedanzen ab. Als Konsequenz daraus führt die Theorie zur Berechnung verschiedener Materialkonstanten, welche den Einfluss der Verteilung der Einschliessungen in einem lokalen representativen Volumen bestimmter Dimensionen darstellen.

     

Nonlinear flexural response of laminated composite plates under hygro-thermo-mechanical loading

The paper deals with Chebyshev series based analytical solution for the nonlinear flexural response of the elastically supported moderately thick laminated composite rectangular plates subjected to hygro-thermo-mechanical loading. The mathematical formulation is based on higher order shear deformation theory (HSDT) and von-Karman nonlinear kinematics. The elastic foundation is modeled as shear deformable with cubic nonlinearity. The elastic and hygrothermal properties of the fiber reinforced composite material are considered to be dependent on temperature and moisture concentration and have been evaluated utilizing micromechanics model. The quadratic extrapolation technique is used for linearization and fast converging finite double Chebyshev series is used for spatial discretization of the governing nonlinear equations of equilibrium. The effects of Winkler and Pasternak foundation parameters, temperature and moisture concentration on nonlinear flexural response of the laminated composite rectangular plate with different lamination scheme and boundary conditions are presented.     

Nonlinear transient analysis of moderately thick laminated composite sector plates

This study presents a simple formulation for the nonlinear dynamic analysis of shear-deformable laminated sector plates made up of cylindrically orthotropic layers. The non-axisymmetric formulation in cylindrical coordinates is discretized in space domain using two-dimensional Chebyshev polynomials. Houbolt time marching is used for temporal discretization. Quadratic extrapolation is used for linearization along with fixed-point iteration for obtaining the results. Several combinations of simply supported, clamped and free edge conditions are considered. Convergence study has been carried out and the results are compared with the results of square plates. Effects of boundary conditions, moduli ratio, lamination scheme, sector angle and annularity on the transient deflection response are plotted graphically. Transient responses are compared for step, saw-tooth and sinusoidal loadings.     

Polynomial and exponential stability for one-dimensional problem in thermoelastic diffusion theory

We consider one-dimensional problem for the thermoelastic diffusion theory and we obtain polynomial decay estimates. Then we show that the solution decays exponentially to zero as time goes to infinity; that is, denoting by E(t) the first-order energy of the system, we show that positive constants C ₀ and c ₀ exist which satisfy E(t) ≤ C ₀ E(0)e ^{?c ₀ t} .