الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
An improved layerwise theory is established for the bending and vibration responses of multi-layered functionally graded doubly curved shells with material properties varying gradually and continuously across the whole shell thickness. The theory accounts for shear deformation and normal strain effects by assuming for each layer, a displacement field with zigzag first-order in-plane displacements and through-the-thickness parabolic transverse displacement. Moreover, it is assumed a stress field satisfying the loading conditions on the external shell faces and the continuity conditions of the internal stresses at the layers interfaces, so, there is no need for introducing in the present formulation any shear correction factor. For this purpose, a mixed variational statement is used. The continuity conditions for the displacements at the layers interfaces are used to decrease the degrees of freedom of the theory. Bending and free vibration problems are solved for FGM single- and three-layered sandwich open cylindrical and spherical shells with completely simply supported or clamped edges . Comparisons for some present results with numerical results obtained by other authors due to advanced 2D and 3D elasticity solutions are made showing the high efficiency of the present theory in predicting the bending and vibration parameters. Graphics are presented to demonstrate the importance of the normal strain effect for the static bending and free vibration of the considered shells. Also, A consistent layerwise model is established for multilayered truncated conical shells reinforced by carbon nanotubes (CNTs). In all layers, the material properties are taken to be continuous across the thicknesses and at their interfaces. For this purpose, a modified mixed variational statement has been utilized including stresses consistent with the shell continuous elastic properties, as well as, with the surface loadings on the external shell faces. A continuous displacement field is introduced for each layer involving shear deformations and through-thickness stretching stains, and it varies across the layer thickness according to sine and cosine trigonometric functions. Consequently, the rationale for using any shear correction factor is abbreviated. Free vibrations are investigated for single- and multi-layer truncated conical shells reinforced by CNTs across the shell thickness with different functionally graded (FG) schemes. An assessment for the accuracy of the present formulation is made by comparing some present results for frequency parameters with their corresponding published ones. The effect of the thickness stretching strains on the free vibrations of CNT-reinforced cylindrical and conical shells is demonstrated.