• Composites Research
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• v.12 no.4
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• pp.17-24
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• 1999

Finite element analysis and experiment are performed to investigate residual deformation induced by the repair of composite shell structures using a prepreg patch method. The finite element program is developed on the basis of a three-dimensional degenerated shell element and the first order shear deformation theory. The results analyzed for the laminated shell with free boundary conditions are compared with strains measured during the prepreg patch repair. Final residual stresses occur greatly near the patch when the laminated shell with all edges clamped is repaired using the prepreg patch. Stacking sequences of the laminated shell and patch affect significantly the residual stresses which occur even if they are the same.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.475-484
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• 1999

압력절점은 요소의 균등한 압력증분을 1개의 자유도로 갖는 절점이며, 유한요소의 하중-변위 평형방정식에 체적과 압력의 관계를 추가하여 한계압력 이후에서도 체적변화에 따른 압력증분을 직접적으로 제저할 수 있는 절점이다. 본 연구에서는 철근콘크리트의 평면 구성 방정식과 적층정식화에 적용한 쉘 요소에 압력절점을 추가하고 해석시 체적을 제어함으로써 철근콘크리트 원통형 구조에 대해 파괴까지의 극한내압 능력을 해석할 수 있는 체적제어 비선형 해석기법을 개발하였다. 본 논문에서 제안한 해석기법을 이용하여 철근콘크리트 원통형 구조물에 대하여 비선형 해석을 수행하여 한계압력과 한계압력 이후의 구조물의 거동을 예측하였으며 실험결과와 비교 검증하였다.

• Computational Structural Engineering
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• v.8 no.3
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• pp.135-141
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• 1995

Any arbitrarily shaped laminated composite shells of revolution can be sum of the conical shell elements. Therefore, finite element model of conical shell element will be developed in this study. To verify consistency and validity of this model, natural vibrations of this model is compared with the analytical solution of cylindrical shell. Herein, an extensive parametric study is presented to assess the modeling capability of this model in class of laminated composite cylinders. It is seen that the proposed model provides highly accurate results with analytical solution. Once development of this conical shell element is done, any arbitrarily shaped composite shells of revolution can be easily analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5979-5986
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• 2013

This study carried out a geometrical nonlinear dynamic analysis of laminated composite shell structures. Based on the first-order shear deformation shell theory and nonlinear formulation of Sanders, the Newmark method and Newton-Raphson iteration are used for dynamic solution considering nonlinear effects. The effects of radius, fiber angles, and layup sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite plates, and the new results reported in this paper show the significant interactions between the radius, fiber angles and layup sequence in the laminate. Key observation points are discussed and a brief design guideline of laminated composite shells is given.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.3
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• pp.279-293
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• 2004

The analysis of linear static and free vibration problems of isotropic and laminated composite plates and shells is performed by the improved 9-node shell element with the new strain displacement relationship. In that relationship, the effect of new additional terms between the bending strain and displacement has been investigated in the warping problem. Natural co ordinate based strains, stresses and constitutive equations are used. The assumed natural strain method is used to alleviate both membrane and shear locking behavior from the element. The Lanczos method is employed in the calculation of the eigenvalues of laminated composite structures and the Gauss integration rule is adopted to evaluate the mass matrix. The numerical examples are compared with the analytical solutions to validate the current formulation and the results presented could be useful for the understanding of the behaviour of laminates under free vibration conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.191-203
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• 2006

The vibration characteristics of composite stiffened laminated plates with stiffener is presented using the assumed natural strain 9-node shell element. To compare with previous research, the stiffened plates are composed of carbon-epoxy composite laminate with a symmetric stacking sequence. Also, the result of the present shell model for the stiffener made of composite material is compared with that of the beam model. In the case of torsionally weak stiffener, a local buckling occurs in the stiffener. In this case, the stiffener should be idealized by using the shell elements. The current investigation concentrates upon the vibration analysis of rectangular stiffened and unstiffened composite plates when subjected to the in-plane compression and shear loads. The in-plane compression affect the natural frequencies and mode shapes of the stiffened laminated composite plates and the increase in magnitude of the in-plane compressive load reduces the natural frequencies, which will become zero when the in-plane load is equal to the critical buckling load of the plate. The natural frequencies of composite stiffened plates with shear loads exhibit the higher values than the case of without shear loads. Also, the intersection, between the curves of frequencies against in-plane loads, interchanges the sequence of some of the mode shapes as a result of the increase in the inplane compressive load. The results are compared with those available in the literature and this result shows that the present shell model for the stiffened plate gives more accurate results. Therefore, the magnitude, direction type of the in-plane shear and compressive loads in laminated composite stiffened plates should be selected properly to control the specific frequency and mode shape. The Lanczos method is employed to solve the eigenvalue problems.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.2
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• pp.212-213
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• 2005

• Computational Structural Engineering
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• v.7 no.2
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• pp.101-109
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• 1994

A degenerated cylindrical shell element for modeling glass fiber reinforced plastic pipes is developed and its performance for static structural analysis under internal uniform pressure is evaluated. The element is a nine node degenerated solid shell element with reduced integration technique, addition of nonconforming displacement modes, and assumed strain method to improve convergence of analysis. Several numerical examples are solved and compared with analytical solutions and other F.E.M programs, The results show that the increment of fiber orientation in the GFRP pipes with reference to the longitudinal axis cause less radial displacements and much stiffness in the pipes. This is reasonable since the internal pressure will primarily cause hoop stresses in the ring and 90-angle ply GFRP ring carry these efficiently in pure tension.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.382-388
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• 2010

This paper describes the standardized finite element model for carbody structures of railway vehicle made of sandwich composites. Recently, sandwich composites were widely used to railway vehicle due to the improvement of energy efficiency, high specific stiffness and strength, weight reduction and space saving in korea. Therefore, structural integrity should be verified using finite element analysis prior to the manufacture of composite railway vehicle. The standardized finite element model for composite carbody structures was introduced through comparing the results of real structural test under vertical, compressive, twisting load and natural frequency test of various railway vehicles in this study. The results show that the quadratic shell element is suitable to model the reinforced metal frame used to improve the flexural stiffness of sandwich panel compared to beam element, and layered shell and solid element are recommended to model the skin and honeycomb core of sandwich panel compared to sandwich shell element. Also, the proposed standard finite element model has the merit of being applied to crashworthiness problem without modifications of finite element model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.3
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• pp.1-10
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• 1991

The paper is concerned with the analysis of laminated composite shell structures using an improved degenerated shell element. In the formulation of the element stiffness, the combined use of three different techniques was made. They are; 1) an enhanced interpolation of transverse shear strains in the natural coordinate system to overcome the shear locking problem; 2) the reduced integration technique in in-plane strains to avoid the membrane locking behavior; and 3) selective addition of the nonconforming displacement modes to improve the element performances. This element is free of serious shear/membrane locking problems and undesirable compatible/commutable spurious kinematic deformation modes. An incremental total Lagrangian formulation is presented which allows the calculation of arbitrarily large displacements. The resulting non-linear equilibrium equations are solved by the Newton-Raphson method. The versatility and accuracy of this improved degenerated shell element are demonstrated by solving several numerical examples.