Showing papers by "J. N. Reddy published in 1983"

Geometrically nonlinear transient analysis of laminated composite plates

Abstract: Forced motions of laminated composite plates are investigated using a finite element that accounts for the transverse shear strains, rotary inertia, and large rotations (in the von Karman sense). The present results when specialized for isotropic plates are found to be in good agreement with those available in the literature. Numerical results of the nonlinear analysis of composite plates are presented showing the effects of plate thickness, lamination scheme, boundary conditions, and loading on the deflections and stresses. The new results for composite plates should serve as bench marks for future investigations. mation are assumed to remain straight and normal to the midsurface after deformation (i.e., transverse shear strains are zero), has been used to calculate frequencies, static response, and dynamic response under applied loads. Recent studies in the analysis of plates have shown that the effect of the transverse shear strains on the static and dynamic response of plates is significant. For example, the natural frequencies of vibration predicted by the classical plate theory are 25% higher, for plate side-to-thickness ratio of 10, than those predicted by a shear deformation theory (SDT). In transient analysis of plates the classical plate theory predicts unrealistically large phase velocities in the plate for shorter wavelengths. The Timoshenko beam theory,3 which includes transverse shear and rotary inertia effects, has been extended to isotropic plates by Reissner 4'5 and Mindlin,6 and to laminated anisotropic plates by Yang et al.7 A generalization of the von Karman nonlinear plate theory for isotropic plates to include the effects of transverse shear and rotary inertia in the theory of orthotropic plates is due to Medwadawski,8 and that for anisotropic plates is due to Ebcioglu.9 With the increased application of advanced fiber composite material to jet engine fan or compressor blades, and in high performance aircraft, studies involving transient response of plates made of such materials are needed to assess the capability of these materials to withstand the forces of impact due to foreign objects (e.g., the ingestion of stones, nuts and bolts, hailstones, or birds in jet engines). Previous in- vestigations into the linear transient analysis of composite plates include Moon's10'11 investigation of the response of infinite laminated plates subjected to transverse impact loads at the center of the plate; Chow's12 study of laminated plates (with transverse shear and rotary inertia) using the Laplace transform technique; the Wang et al. 13 investigation, by the method of characteristi cs, of unsymmetrical orthotropic laminated plates; and Sun and Whitney's14'15 study of plates under cylindrical bending. More recently, the present author16'17 investigated the linear transient response of layered anisotropic composite rectangular plates and presented extensive numerical results for center deflection and stresses.

Dynamic (transient) analysis of layered anisotropic composite‐material plates

Abstract: A shear-flexible finite element is employed to investigate the transient response of isotropic, orthotropic and layered anisotropic composite plates. Numerical convergence and stability of the element is established using Newmark's direct integration technique. Numerical results for deflections and stresses are presented for rectangular plates under various boundary conditions and loadings. The parametric effects of the time step, finite element mesh, lamination scheme and orthotropy on the transient response are investigated. The present results agree very closely with the results available in the literature for isotropic plates, and the results for composite plates should serve as bench marks for future comparisons by other investigators.

Mechanics of bimodular composite structures

Abstract: This paper is a survey of the mechanics of beam and plate structures laminated of fiber-reinforced composite materials having different elastic and thermoelastic properties in tension and compression. Examples of such materials include tire cord-rubber, wire-reinforced solid propellants, and soft biological materials. Specific topics covered include: mathematical models of fiber-reinforced bimodular materials and their experimental verification; static and dynamic analysis of laminated and sandwich beams; plane elasticity; analysis of deflection and free and transient vibration of laminated plates and shells. In all of these analyses, thickness-shear deformation and rotatory inertia are included. The solution methods used include closed-form, transfer-matrix, and finite-element techniques.

Impact on Laminated Composite Plates: A Review of Recent Computational Developments

Abstract: A review of the literature on high velocity impact calculations is presented, with emphasis on laminated composite plates. A summary of results of the geometrically nonlinear transient analysis of layered anisotorpic composite plates is presented.

Geometrically nonlinear analysis of layered composite plates and shells

Abstract: A degenerated three dimensional finite element, based on the incremental total Lagrangian formulation of a three dimensional layered anisotropic medium was developed. Its use in the geometrically nonlinear, static and dynamic, analysis of layered composite plates and shells is demonstrated. A two dimenisonal finite element based on the Sanders shell theory with the von Karman (nonlinear) strains was developed. It is shown that the deflections obtained by the 2D shell element deviate from those obtained by the more accurate 3D element for deep shells. The 3D degenerated element can be used to model general shells that are not necessarily doubly curved. The 3D degenerated element is computationally more demanding than the 2D shell theory element for a given problem. It is found that the 3D element is an efficient element for the analysis of layered composite plates and shells undergoing large displacements and transient motion.

A mixed finite element for the analysis of laminated plates

Abstract: A new mixed shear-flexible finite element based on the Hellinger-Reissner's variational principle is developed. The element is constructed using a mixed formulation of the shear deformation theory of laminated composite plates, and consists of three displacements, two shear rotations, and three moments as the independent degrees of freedom. The numerical convergence and accuracy characteristics of the element are investigated for bending of laminated anisotropic composite plates. The element is relatively simple to construct and has better accuracy and convergence features when compared to other conventional finite elements.

Three-Dimensional Analysis of Composite Plates with Material Nonlinearity.

Abstract: : The study deals with a fully three-dimensional analysis of laminated composite plates accounting for material nonlinearity. The finite-element method with trilinear interpolation of the three displacements is used to model layers of the laminate (both in the plane of laminae and through the thickness of the laminate). The modified Romberg-Osgood material constitutive relations is used to update the principal moduli in the plane of the laminate. The elastic-plastic model with Hill's criteria for anisotropic criteria is also used to analyze laminates. The shear deformable plate-theory element is also used in the study. (Author)

Nonlinear Analysis of Laminated, Bimodular Composite Material Structures.

Abstract: : Geometrically nonlinear analyses of BCM structures; experimental investigations of BCMs and structures; analyses of structures made of nonlinear composite materials, and new structural analyses. The research program was reported in a series of thirty-seven technical reports (including the present one) and sixty-eight conference papers and journal articles, all of which are listed herein. (Author)

Large deformation analysis of layered composite shells

Abstract: A three-dimensional element based on the total Lagrangian description of large deformations of a layered anisotropic composite medium is developed, validated, and used to analyze layered composite shells The element contains the following features: geometric nonlinearity, dynamic (transient) behavior, and arbitrary lamination scheme and lamina properties Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element