• Journal of the Korea Safety Management & Science
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• v.6 no.1
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• pp.311-323
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• 2004

This paper is to study the energy absorption characteristics of CF/Epoxy(Carbon Fiber/Epoxy Resin) laminated shell with the various curvatures subjected to transverse impact loadings under the low impact velocity in consideration of design of structural members for use of transportation machine, which are consisted of the characteristics of high stiffness, strength and lightweight. The curvature radius are associated with the energy absorption characteristics of CF/Epoxy laminated shell which is brittleness material. In all tests, maximum load of CF/Epoxy laminated plate is higher than that of laminated shell with curvature, but maximum deflection is lower. And then absorbed energy of laminated shell with curvature is higher than laminated plate(curvature radius is unlimited), As curvature radius is increased, the absorbed energy is increased in laminated shell with curvature.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.2
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• pp.164-171
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• 2005

This study aims to examine an effect of stacking sequence and curvature on the penetration characteristic of a composite laminated shell. For the purpose, we manufactured specimens with different stacking sequences and curvatures, and conducted a penetration test using an air-gun. To examine an influence according to stacking sequence, as flat plate and curvature specimen had more plies, their critical penetration energy was higher, Critical penetration energies of specimen A and C with less interfaces somewhat higher than those of B and D with more interfaces. The reason that with less interfaces, critical penetration energy was higher is pre-impact bending stiffness of composite laminated shell with less interfaces was lower than that of laminated shell with more interfaces, but bending stiffness after impact was higher. And it is because interface, the weakest part of the composite laminated shell, was influenced by transverse impact. As curvature increases, critical penetration energy increases linearly. It is because as curvature increases, resistance to in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. Patterns of cracks caused by penetration of composite laminated shells include interlaminar crack, intralaminar crack, and laminar fracture. A 0$^{\circ}$ply laminar had a matrix crack, a 90$^{\circ}$ply laminar had intralaminar crack and laminar fracture, and interface between 0$^{\circ}$and 90$^{\circ}$laminar had a interlaminar crack. We examined crack length and delamination area through a penetration test. For the specimen A and C with 2 interface, the longest circumferential direction crack length and largest delamination area were observed on the first interface from the impact point. For the specimen B and D with 4 interface, the longest crack length and largest delamination area were observed on the third interface from the impact point.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.119-125
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• 1997

The finite element analysis of plate and shell structures has been one of the major research interests for many years because of the technological importance of such structures. Quite often these structures are constructed by laminated composites. This is due to the high specific stiffness and strength of composite structures. The main objective of this paper is to extend the use of an improved degenerated shell element to the large displacement analysis of plates and shells with laminated composites. The total Lagrangian approach has been chosen for the definition of the deformation and the solution to the nonlinear equilibrium equations is obtained by the Newton-Raphson method.

• Journal of Korean Society of Steel Construction
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• v.9 no.1 s.30
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• pp.3-11
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• 1997

Laminated composite shells exhibit properties comsiderably different from those of the single-layer shell. Thus, to obtain the more accurate solutions to laminated composite shells ptoblems, effects of shear strain should be condidered in analysis of them. A higher-order shear deformation theory requires no shear correction coefficients. This theory is used to determine the buckling loads of elastic shells. The theory accounts for parabolic distribution of the transverse shear through the thickness of the shell and rotary inertia. Exact solutions of simply-supported shells are obtained and the results are compared with the exact solutions of the first-order shear deformation theory, and the classical theory. The present theory predicts the buckling loads more accurately when compared to the first -order and classical theory.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.10a
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• pp.69-72
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• 2004

A new three-node triangular shell element based on higher order zig-zag theory is developed for laminated composite shells with multiple delaminations. The present higher order zig-zag shell theory is described in a general curvilinear coordinate system and in general tensor notation. All the complicated curvatures of surface including twisting curvatures can be described in an exact manner in the present shell element because this element is based on geometrically exact surface representation. The displacement field of the proposed finite element includes slope of deflection, which requires continuity between element interfaces. Thus the nonconforming shape function of Specht's three-node triangular plate bending element is employed to interpolate out-of-plane displacement. The present element passes the bending and twisting patch tests in flat surface configurations. The developed element is evaluated through the eigenvalue problems of composite cylindrical shells with multiple delaminations. Through the numerical examples it is demonstrated that the proposed shell element is efficient because it has minimal degrees of freedom per node. The present shell element should serve as a powerful tool in the prediction of natural frequency and modes of multi-layered thick laminated shell structures with arbitrary-shaped multiple delaminations.

• 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.

• Steel and Composite Structures
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• v.22 no.2
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• pp.301-321
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• 2016

The objective of this paper is to investigate buckling behavior of composite laminated cylinders by using semi-analytical finite strip method. The shell is subjected to deformation-dependent loads which remain normal to the shell middle surface throughout the deformation process. The load stiffness matrix, which is responsible for variation of load direction, is also throughout the deformation process. The shell is divided into several closed strips with alignment of their nodal lines in the circumferential direction. The governing equations are derived based on the first-order shear deformation theory with Sanders-type of kinematic nonlinearity. Displacements and rotations of the shell middle surface are approximated by combining polynomial functions in the meridional direction and truncated Fourier series along with an appropriate number of harmonic terms in the circumferential direction. The load stiffness matrix, which is responsible for variation of load direction, is also derived for each strip and after assembling, global load stiffness matrix of the shell is formed. The numerical illustrations concern the pressure stiffness effect on buckling pressure under various conditions. The results indicate that considering pressure stiffness causes buckling pressure reduction which in turn depends on various parameters such as geometry and lay-ups of the shell.

• 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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.969-974
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• 1994

The dynamic behavior of graphite/epoxy laminated composite shell structure due to low-velocity impact is investigated using the finite element method. In this analysis, the Newmark's constant-acceleration time integration algorithm is used. The impact response such as contact force, central deflection and dynamic strain history form shell structure analysis are compared with those form the plate non-linear analysis. The effects of curvature, impact velocity and mass of impactor on the composite shell are discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.8
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• pp.2051-2060
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• 1993

A finite element program using degenerated shell element was developed to solve the geometric, material and combined nonlinear behaviors of composite laminated shell. The total Lagrangian method was implemented for geometric nonlinear analysis. The material nonlinear behavior was analyzed by considering the matrix degradation due to the progressive failure in the matrix and matrix-fiber interface after initial failure. The result of the geometric nonlinear analysis showed good agreement with the other exact and numerical solutions. The results of the combined analyses considered both geometric and material nonlinear analyses were compared with the experiments in which internal pressure was applied to the filament wound antisymmetric tubes.