• Journal of the Korean Society for Precision Engineering
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• v.30 no.7
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• pp.769-776
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• 2013

The dynamic compliance characteristics of a prosthetic foot midgait are very important for natural performance in an amputee's gait and should be in a range that provides natural, stable walking. In this study, finite element analysis (FEA) and classical laminate theory were used to examine the mechanical characteristics of a carbon-epoxy composite laminate prosthetic foot as a function of variation in the lamination composition. From this analysis, an FEM model of a prosthetic keel, made from the composite material, was developed. The lamination composition of the keel was designed for improved stiffness. The prototype product was fabricated using an autoclave. Vertical loading response tests were performed to verify the simulation model. The results of the experiments were similar to those from simulations below the loading level of the gait, suggesting use of the proposed simulation model for prosthetic keel design.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.197-200
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• 2001

A manufacturing process of composite pressure vessel was studied. The vessel was fabricated using the filament winding process. It is utilized as a container of high pressure Helium gas which propels a rocket fuel and an oxidizer. The layup patterns were determined based on the lamination theory. 3-axis controlled filament winding machine was developed to realize the patterns. The vessel was successfully fabricated using the developed machine. And the hydraulic pressure test was performed to measure an applied pressure-strain relations on the composite vessel.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.667-676
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• 1998

The transient analysis of partially supported laminated plates with rectangular holes under uniformly distributed transverse load is studied using finite element method. The first-order shear deformation theory and the variational energy method are employed in mathematical formulation. The effects on central deflection by plate thickness ratio, material modulus ratio, ply lamination geometry and boundary conditions are investigated Numerical results are presented and comparisons of the results by the present method with those given in the literature are made.

• Steel and Composite Structures
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• v.9 no.5
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• pp.473-497
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• 2009

For the spatially coupled free vibration analysis of composite box beams resting on elastic foundation under the axial force, the exact solutions are presented by using the power series method based on the homogeneous form of simultaneous ordinary differential equations. The general vibrational theory for the composite box beam with arbitrary lamination is developed by introducing Vlasov°Øs assumption. Next, the equations of motion and force-displacement relationships are derived from the energy principle and explicit expressions for displacement parameters are presented based on power series expansions of displacement components. Finally, the dynamic stiffness matrix is calculated using force-displacement relationships. In addition, the finite element model based on the classical Hermitian interpolation polynomial is presented. To show the performances of the proposed dynamic stiffness matrix of composite box beam, the numerical solutions are presented and compared with the finite element solutions using the Hermitian beam elements and the results from other researchers. Particularly, the effects of the fiber orientation, the axial force, the elastic foundation, and the boundary condition on the vibrational behavior of composite box beam are investigated parametrically. Also the emphasis is given in showing the phenomenon of vibration mode change.

• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.137-147
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• 2014

The present paper deals with the first ply failure analysis of the laminated composite plates under various static and dynamic loading conditions. Static analysis has been carried out under patch load and triangular load. The dynamic failure analysis has been carried out under triangular pulse load. The formulation has been carried out using the finite element method and a computer code has been developed. The first order shear deformation theory has been applied in the present formulation. The displacement time history analysis of laminated composite plate has been carried out and the results are compared with those published in literature to validate the formulation. The first ply failure load for laminated composite plates with various lamination schemes under static and dynamic loading conditions has been calculated using various failure criteria. The failure index-time history analysis has also been carried out and presented in this paper.

• Korean Journal of Computational Design and Engineering
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• v.1 no.2
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• pp.107-121
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• 1996

An optimization procedure is proposed to determine the optimal stacking sequence on the buckling of laminated composite plates with midplane symmetry under various loading conditions. Classical lamination theory is used for the determination of the critical buckling load of simply supported angle-ply laminates. Analysis is performed by the Galerkin method and Rayleigh-Ritz method. The approximate solution of buckling is replaced by the algorithms that produce generalized eigenvalue problem. Direct search technique is employed to solve the optimization problem effectively. A series of computations is carried out for plates having different aspect ratios, different load ratios and different number of lay-ups.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.179-182
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• 2002

Rapid Prototyping (RP) technologies provide the ability to fabricate initial prototypes from various model materials. Stratasys' Fused Deposition Modeling (FDM) is a typical RP process that can fabricate prototypes out of plastic materials, and the parts made from FDM were often used as load-carrying elements. Because FDM deposits materials in about $300\mutextrm{m}$ thin filament with designated orientation, parts made from FDM show anisotropic material properties. This paper proposes an analytic model to predict the tensile strength of FDM parts. Applying the Classical Lamination Theory, which was developed for laminated composite materials, a computer code was implemented. Tsai-Wu failure criterion was added to the code to predict the failure of the FDM parts. The tensile strengths predicted by the analytic model were compared with experimental data. The data and prediction agreed reasonably well to prove the validity of the model. In addition, a web-based advisory service was developed to provide to strength prediction and design rules for FDM parts.

• Steel and Composite Structures
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• v.20 no.5
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• pp.1087-1102
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• 2016

The paper proposes to characterize the free vibration behaviour of non-uniform cylindrical shells using spline approximation under first order shear deformation theory. The system of coupled differential equations in terms of displacement and rotational functions are obtained. These functions are approximated by cubic splines. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector which are spline coefficients. Four and two layered cylindrical shells consisting of two different lamination materials and plies comprising of same as well as different materials under two different boundary conditions are analyzed. The effect of length parameter, circumferential node number, material properties, ply orientation, number of lay ups, and coefficients of thickness variations on the frequency parameter is investigated.

• Steel and Composite Structures
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• v.17 no.3
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• pp.305-320
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• 2014

The lowest critical value of the compressive force acting in the plane of symmetrically laminated quasi-isotropic thin rectangular plates is investigated. The critical buckling loads of plates with different types of lamination and aspect ratios are parametrically calculated. Finite Differences Method (FDM) and Galerkin Method are used to solve the governing differential equation for Classical Laminated Plate Theory (CLPT). The results calculated are compared with those obtained by the software ANSYS employing Finite Elements Method (FEM). The results of Galerkin Method (GM) are closer to FEM results than those of FDM. In this study, the primary aim is to conduct a parametrical performance analysis of proper plates that is typically conducted at preliminary structural design stage of composite vessels. Non-dimensional values of critical buckling loads are also provided for practical use for designers.

• Structural Engineering and Mechanics
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• v.74 no.5
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• pp.577-588
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• 2020

A unified solution is presented for the buckling analysis of rectangular laminated composite plates with elastically restrained edges. The plate is subjected to biaxial in-plane compression, and the boundary conditions are simulated by employing uniform distribution of linear and rotational springs at all edges. The critical values of buckling loads and corresponding modes are calculated based on classical lamination theory and using the Ritz method. The deflection function is defined based on simple polynomials without any auxiliary function. The verifications of the current study are carried out with available combinations of classic boundary conditions in the literature. Through parametric study with a wide range of spring factors with some classical as well as some not classical boundary conditions, competency of the present model of boundary conditions is proved.