Stability of parametric vibrations of laminated composite plates
The dynamic stability of laminated composite plates subjected to arbitrary periodic loads is studied based on the first-order shear deformation plate theory. The in-plane load is taken to be a combination of periodic biaxial and bending stress. A set of second-order ordinary differential equations with periodic coefficients of Mathieu-Hill type is formed to determine the regions of dynamic instability based on Bolotin's method. Numerical results reveal that the dynamic instability is significantly affected by the modulus ratio, number of layer, static and dynamic load parameters. The effects of various important parameters on the instability region and dynamic instability index are investigated.
INTERACTION CURVES FOR COMPOSITE LAMINATES SUBJECTED TO BIAXIAL IN-PLANE LOADS
In this study, an attempt has been made to incorporate the effect of transverse shear on the stability analysis of moderately thick/very thick composite laminated plates under in-plane compressive loading using a "Simple Higher-Order Shear Deformation Theory" based on four unknown displacement functions (u0, v0, wb, ws) instead of five which is commonly used in most of the higher-order theories. The finite element method is employed to study the initial buckling load of laminated plates. The change in initial buckling response of thick rectangular anti-symmetric laminates with respect to the fiber orientation angle has been studied. The interaction curves (between Nx and Ny for different parameters of the laminates) are studied in detail. The interaction curves for Nx and Ny are either linear or piecewise linear. There are some combinations of biaxial in-plane loads for which laminates with different lay-up sequences have the same initial buckling loads.
Dynamic Stability Of Stiffened Laminated Composite Plates And Shells Subjected To In-Plane Pulsating Forces
Abstract The dynamic stability of laminated composite stiffened or non-stiffened plates and shells due to periodic in-plane forces at boundaries is investigated in this paper. The 3-D degenerated shell element and 3-D degenerated curved beam element are used to model plates/shells and stiffeners, respectively. The characteristic equations for the natural frequencies, buckling loads and their corresponding mode shapes are obtained from the finite element equations of motion. Then, the method of Hill's infinite determinants or the method of multiple scales is applied to analyze the dynamic instability regions. Numerical results are presented to demonstrate the effects of various parameters, such as skew angle, lamination scheme, stiffening scheme, in-plane force type and the curvature of the cylindrical shells, on the dynamic stability of stiffened and non-stiffened plates and shells subjected to in-plane pulsating forces at boundaries.