• Advanced Composite Materials
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• v.18 no.1
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• pp.21-42
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• 2009

The vibration characteristics of post-buckled laminated composite doubly curved shells are investigated. The finite element method is used for the analysis of post-buckling and free vibration of post-buckled laminated shells. The geometric non-linear finite element model includes the general non-linear terms in the strain-displacement relationships. The shell geometry used in the present formulation is derived using an orthogonal curvilinear coordinate system. Based on the principle of virtual work the non-linear finite element equations are derived. Arc-length method is implemented to capture the load-displacement equilibrium curve. The vibration characteristics of post-buckled shell are performed using tangent stiffness obtained from the converged deflection. The code is first validated and then employed to generate numerical results. Parametric studies are performed to analyze the snapping and vibration characteristics. The relationship between loads and fundamental frequencies and between loads and the corresponding displacements are determined for various parameters such as thickness ratio and shallowness.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.128-133
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• 2001

In this paper, stability analysis is carried out far the out of plane behaviors under compressive loads to the conical direction. It is not easy to obtain the analytic solutions about the stability analysis of anisotropic conical shells consisted of composite materials. For solving this problems, this paper used the finite difference method which is one of the numerical methods. The characteristics of the buckling behaviors of anisotropic laminated composite conical shells may be different according to a variety of causes, that is, the change of fiber angle, material arrangement, radius ratio, shape ratio and so on. The objective of this study is to analyze buckling behaviors of circular conical shells with shear deformation effects and to prove the advantage of composite materials.

• Structural Engineering and Mechanics
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• v.43 no.1
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• pp.89-103
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• 2012

In this study, the stability of laminated homogeneous and non-homogeneous orthotropic truncated conical shells with freely supported edges under a uniform hydrostatic pressure is investigated. It is assumed that the composite material is orthotropic and the material properties depend only on the thickness coordinate. The basic relations, the modified Donnell type stability and compatibility equations have been obtained for laminated non-homogeneous orthotropic truncated conical shells. Applying Galerkin method to the foregoing equations, the expression for the critical hydrostatic pressure is obtained. The appropriate formulas for the single-layer and laminated, cylindrical and complete conical shells made of homogeneous and non-homogeneous, orthotropic and isotropic materials are found as a special case. Finally, effects of non-homogeneity, number and ordering of layers and variations of shell characteristics on the critical hydrostatic pressure are investigated.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.9
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• pp.797-805
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• 2013

In this paper vibration and stability analysis of laminated composite shells based on the first order shear deformation theory(FSDT) for two different boundary conditions(clamped-clamped, simply supported) are performed. Structural model of cross-ply symmetric laminated composite cylindrical shells subjected to a combination of magnetic and thermal fields is developed via Hamilton's variational principle. These coupled equations of motion are based on the electromagnetic equations(Faraday, Ampere, Ohm, and Lorenz equations)and thermal equations which are involved in constitutive equations. Extended Galerkin method is adopted to obtain the discretized equations of motion. Variations of dynamic characteristics of composite shells with applied magnetic field, temperature gradient, laminate thickness-ratio and radius ratio for two boundary conditions are investigated and pertinent conclusions are derived.

• Structural Engineering and Mechanics
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• v.84 no.6
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• pp.707-722
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• 2022

In this study, a new refined hyperbolic shear deformation theory (RHSDT) is developed using an equivalent single-layer shell displacement model for the static bending and free vibration response of cross-ply laminated composite spherical shells. It is based on a new kinematic in which the transverse displacement is approximated as a sum of the bending and shear components, leading to a reduction of the number of unknown functions and governing equations. The proposed theory uses the hyperbolic shape function to account for an appropriate distribution of the transverse shear strains through the thickness and satisfies the boundary conditions on the shell surfaces without requiring any shear correction factors. The shell governing equations for this study are derived in terms of displacement from Hamilton's principle and solved via a Navier-type analytical procedure. The validity and high accuracy of the present theory are ascertained by comparing the obtained numerical results of displacements, stresses, and natural frequencies with their counterparts generated by some higher-order shear deformation theories. Further, a parametric study examines in detail the effect of both geometrical parameters (i.e., side-to-thickness ratio and curvature-radius-to-side ratio), on the bending and free vibration response of simply supported laminated spherical shells, which can be very useful for many modern engineering applications and their optimization design.

• Structural Engineering and Mechanics
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• v.13 no.6
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• pp.695-711
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• 2002

Here, the dynamic response characteristics of thick cross-ply laminated composite cylindrical shells are studied using a higher-order displacement model. The formulation accounts for the nonlinear variation of the in-plane and transverse displacements through the thickness, and abrupt discontinuity in slope of the in-plane displacements at any interface. The effect of inplane and rotary inertia terms is included. The analysis is carried out using finite element approach. The influences of various terms in the higher-order displacement field on the free vibrations, and transient dynamic response characteristics of cylindrical composite shells subjected to thermal and mechanical loads are analyzed.

• Structural Engineering and Mechanics
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• v.13 no.4
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• pp.387-410
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• 2002

Formulation of an 8 nodes assumed strain shell element is presented for the analysis of shells. The stiffness matrix based on the Mindlin-Reissner theory is analytically integrated through the thickness. The element is free of membrane and shear locking behavior by using the assumed strain method such that the element performs very well in modeling of thin shell structures. The material is assumed to be isotropic and laminated composite. The element has six degrees of freedom per node and can model the stiffened plates and shells. A great number of numerical testing carried out for the validation of present 8 node shell element are in good agreement with references.

• Journal of the Korean Society of Safety
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• v.19 no.1
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• pp.94-101
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• 2004

In this study, composite laminated conical shells with ring stiffeners are analyzed. A versatile 4-node shell element which is useful for the analysis of conical shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. The proposed element has six degrees of freedom per node and permits an easy connection to other types(beam element) of Optimum location and optimum section properties of ring stiffeners are obtained. It is shown that the thickness of conical shell is reduced about 20% by optimum ring stiffeners.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.6
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• pp.12-18
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• 1998

The optimal design for stiffened laminate composite cylindrical shells under combined loads is studied by a nonlinear mathematical search algorithm. The optimal design is accomplished with the CONMIN. several types of buckling modes with maximum allowable stresses and strains are included as constraints in the optimal design process, such as general buckling, panel buckling with either stringers or rings smeared out, local skin buckling, local crippling of stiffener segments. Rectangular or T type stringers and rectangular rings are used for stiffened laminate composite cylindrical shells.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.475-485
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• 2001

A study on the structural analysis of the composite laminated cylindrical shell which has simply supported boundary conditions at both ends, was performed. The results were used into the neural networks. Neural networks identify the load characteristics of the composite shells. Momentum Backpropagation which the learning rate can be varied was developed. Input patterns consist of strains at 9 side points which is divided equally. Output layers are the load characteristics. Developed program was used for the training. The training with variable learning rate was converged close to real oad characteristics. Inverse engineering can be applicable to the composite laminated cylindrical shells with developed neural networks.