Composite Annular Plates Research Articles

Study of critical buckling loads and modes of cross-ply laminated annular plates

Buckling of composite annular plates under uniform internal and external radial edge loads have been investigated using energy method. Trefftez rule is used in the stability equations. The symmetric buckling of symmetric cross-ply laminates is considered. In this paper, buckling behavior for the three laminates (90/0)2s, (90/02/90)s and (902/02)s are studied. Influence of some parameters such as thickness, stacking sequence, type of supports and the ratio of hole to sheet radius on buckling loads and modes are investigated. The results of the energy method are compared with the results of numerical method. Based on the results, in the plates with clamped boundary conditions the symmetric buckling assumption is not accurate, contrary to other boundary conditions.

Nonlinear free vibration of a shear deformable laminated composite annular elliptical plate

The nonlinear free vibration of a laminated composite annular elliptical plate with elliptically orthotropic plies is investigated. The effects of out-of-plane shear deformations, rotatory inertia and geometrical nonlinearity are taken into account. The problem is solved numerically using a new polynomially enriched sector elliptic p-element. The nonlinear equations of free motion are obtained using the harmonic balance method and solved iteratively by the linearized updated mode method. Results for the fundamental linear and nonlinear frequencies are obtained. Comparison is made with published results for a polar orthotropic annular plate and shows very good agreement. The minor semi-axis ratio, thickness ratio, moduli ratio, number of plies, layup sequence, and boundary conditions are shown to influence the hardening behavior.

Free Vibration of Composite Annular Plates Embedded with SMA Fibers in the Circumferential Direction

Based on Brinson’s one-dimensional thermo-constitutive law of SMA and classical plate theory, linear non-axisymmetric vibration of uniform heated composite annular plate embedded with circumferential SMA fibers is investigated. Natural frequencies of the annular plates with immovably clamped boundary condition, depending on the temperature rise are obtained by using shooting method. The characteristic curves of first four natural frequencies of non-axisymmetric vibration versus temperature rise are plotted. Influences of the volume fraction and the initial strain of SMA on the natural frequencies of plate are analyzed. The numerical results show that, the activation of SMA can enhance the natural frequency both in the inverse martensite transformation temperature range and the thermal buckling temperature.

Vibration and damping analysis of a three-layered composite annular plate with a viscoelastic mid-layer

The natural frequencies and modal loss factors of the three-layered annular plate with a viscoelastic core layer and two polar orthotropic laminated face layers are considered. The discrete layer annular finite element is employed to derive the equations of motion for the three-layered annular plate. The viscoelastic material in the central layer is assumed to be incompressible, and the extensional and shear moduli are described by the complex quantities. Complex eigenvalued problems are then solved, and the frequencies and modal loss factors of the composite plate are extracted. The results of the symmetric and non-symmetric composite annular plates are both presented. The effects of material properties, radius to thickness ratio, stacking sequences and thickness of face layers, and thickness of the viscoelastic core layer are discussed.

AXISYMMETRIC VIBRATIONS OF CONCENTRIC DISSIMILAR ORTHOTROPIC COMPOSITE ANNULAR PLATES

The axisymmetric vibrational behaviour of two concentric dissimilar orthotropic composite annuli is investigated. Sixth order systems of equations of motion for each annulus are presented together with the matching conditions at their interface. The common frequency of vibration of the structure is determined numerically using a finite difference method. Bi-layered, triple-layered and bi-+triple-layered material compositions were considered. Computed results for a wide range of possible orthotropic material combinations indicate the complex role the material orthotropies play in determining the annuli's vibrational response. It is shown that the frequency increase factor (defined as the ratio between the highest and lowest frequencies obtained for all inner and outer material combinations considered) is very sensitive to the geometric, heterogeneity and orthotropy parameters of the composite annular plates. Unfortunately, no simple rule of thumb formula for estimating the effect of the material composition on the frequency appears to be deducible. However, in keeping with previous results for concentric dissimilar isotropic annuli, the geometry (expressed via the radii of the inner and outer annuli) and the different material compositions were found to exert a considerable influence on the natural frequency of vibration. In the absence of appropriate analytical expressions, optimization and, thereby, control of the natural frequency of composite plate-like structures, through geometry and material composition, must make use of parametric studies similar to the current one.

On Dynamic State Evaluation at the Boundary of Surface Treated Materials. Composite Annular Thick Plate Sustaining a Twisting Moment Along the Outer Portion.

The present paper is concerned with the torsion problem of composite annular plate the inclusion of which has an equivalent elastic constant. In particular, this paper is concerned with an annular thick plate sustaining a twisting moment along the outer portion. By employing Reissner's thick plate theory, expressions for stresses and displacements near the boundary of the composite annular plate are obtained and appropriate continuity conditions are satisfied at the boundary of that region. Numerical results of a specific example illustrate the marked improvement of the present treatment.

Vibration analysis of composite annular plates by an integral equation technique

In layered plates, coupling between bending and stretching makes the analysis complicated. A numerical method, namely an integral equation technique which has been used for solving static and dynamic problems, is extended to vibration analysis of layered annular plates which are fixed at the inner and outer radii. The results obtained are compared with those of other investigators and a parametric study is made of the effect of layer thickness, the layers being made up of two different materials.