• Korean Journal of Metals and Materials
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• v.46 no.6
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• pp.382-389
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• 2008

To manufacture Al MMCs, in-situ melt mixing process is used because it is free from contamination, and it makes reinforcements homogeneously dispersed. Large eddy simulation method is used to find the optimum melt mixing condition. At the Re 3000, the most suitable mixing is occurred between Al-Ti and Al- B melts. The in-situ formed $TiB_2$ particles has the size varying from 40 nm to 130 nm, due to the increase of cooling rate, and exhibits a homogeneous dispersion. And the interface between reinforcement and matrix is clean. Both hardness and Young's modulus of this composite are improved with increasing the cooling rate.

• Journal of Urban Science
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• v.10 no.1
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• pp.11-20
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• 2021

In this study, the vibration characteristics were theoretically analyzed by modeling a free isotropic rotating disk with an outer periphery with a fixed inner periphery, paying attention to disks used as storage devices for information devices, especially magnetic disks, magneto-optical disks, and compact disks in which the head and disk are non-contact. Iluminate with Composite materials represented by fiber-reinforced plastics (FRP) have high specific strength (strength/density) and specific stiffness (narrowness/density). It is used in the elements, and its use is rapidly expanding. Under this circumstance, the disk currently manufactured using an isotropic material made of various plastic materials such as aluminum or polycarbonate as a base material is an extremely anisotropic material made of a composite material, and the circumferential stiffness of the disk is made of reinforcing fibers in the circumferential direction. It is modeled as an anisotropic rotating disk with increased, and its influence on the vibration characteristics is revealed.

• Steel and Composite Structures
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• v.44 no.3
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• pp.371-388
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• 2022

The present study tackles the problem of forced vibration of imperfect axially functionally graded shell structure with truncated conical geometry. The linear and nonlinear large-deflection of the structure are considered in the mathematical formulation using von-Kármán models. Modified coupled stress method and principle of minimum virtual work are employed in the modeling to obtain the final governing equations. In addition, formulations of classical elasticity theory are also presented. Different functions, including the linear, convex, and exponential cross-section shapes, are considered in the grading material modeling along the thickness direction. The grading properties of the material are a direct result of the porosity change in the thickness direction. Vibration responses of the structure are calculated using the semi-analytical method of a couple of homotopy perturbation methods (HPM) and the generalized differential quadrature method (GDQM). Contradicting effects of small-scale, porosity, and volume fraction parameters on the nonlinear amplitude, frequency ratio, dynamic deflection, resonance frequency, and natural frequency are observed for shell structure under various boundary conditions.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.4
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• pp.11-18
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• 2011

In this study, the performance of a steel-FRP composite bridge safety barrier was evaluated through vehicle crash simulation. Surface veil, DB and Roving fibers were used for FRP. The MAT58 material model provided by LS-DYNA software was used to model FRP material. Spot weld option was used for modeling contact between steel and FRP beam. The structural strength performance, the passenger protection performance, and the vehicle behavior after crash were evaluated corresponding to the vehicle crash manual. As the result, A steel-FRP composite safety barrier was satisfied with the required performance.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1684-1689
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• 2003

This paper concerns the analytical modeling and dynamic analysis of advanced cantilevered blade structure implemented by a dual approach based on structural tailoring and viscoelastic materials technology. Whereas structural tailoring uses the directionality properties of advanced composite materials, the passive materials technology exploits the damping capabilities of viscoelastic material(VEM) embedded into the host structure. The structure is modeled as a composite thin-walled beam incorporating a number of nonclassical features such as transverse shear, secondary warping, anisotropy of constituent materials, and rotary inertias. The case of VEM spreaded over the entire span of the structure is considered. The displayed numerical results provide a comprehensive picture of the synergisitic implications of the application of both techniques, namely, the tailoring and damping technology on vibration response of thin-walled beam structure exposed to external time-dependent excitations.

• Journal of Korean Association for Spatial Structures
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• v.1 no.1 s.1
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• pp.109-115
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• 2001

Composite materials also known as fiber reinforced plastics have been developed and used in many engineering applications due to their outstanding mechanical properties. Laminated plates as structural components that are made of in composite material are widely used. Therefore, nonlinear response of laminated composite plates modeled with finite elements and excited by stochastic loading is studied. The classical laminated plate theory is used to account for the variation of strains through the thickness for modeling laminated thin plates. Approximate nonlinear random vibration analysis is performed using the method of equivalent linearization to account for material non-linearity.

• Structural Engineering and Mechanics
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• v.33 no.6
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• pp.657-674
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• 2009

In this paper a 3-D continuum damage mechanics formulation for composite laminates and its implementation into a finite element model that is based on the layer-wise laminate plate theory are described. In the damage formulation, each composite ply is treated as a homogeneous orthotropic material exhibiting orthotropic damage in the form of distributed microscopic cracks that are normal to the three principal material directions. The progressive damage of different angle ply composite laminates under quasi-static loading that exhibit the free edge effects are investigated. The effects of various numerical modeling parameters on the progressive damage response are investigated. It will be shown that the dominant damage mechanism in the lay-ups of [+30/-30]s and [+45/-45]s is matrix cracking. However, the lay-up of [+15/-15] may be delaminated in the vicinity of the edges and at $+{\theta}/-{\theta}$ layers interfaces.

• Steel and Composite Structures
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• v.28 no.1
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• pp.111-121
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• 2018

It has been argued that fracture energy of composite laminates depends on their thickness and number of layers. In this paper a modified direct energy balance approach (DEBA) has been developed to evaluate the mode-II shear fracture energy for E-glass/Epoxy laminates from finite element model at an arbitrary thickness. This approach considers friction and damage/plasticity deformations using cohesive zone modeling (CZM) and nonlinear finite element modeling. The presence of compressive stress and resulting friction was argued to be a possible cause for the thickness dependency of fracture energy. In the finite element modeling, CZM formulation has been developed with bilinear cohesive constitutive law combined with friction consideration. Also ply element have been developed with shear plastic damage model. Modified direct energy balance approach has been proposed for estimation of mode-II shear fracture energy. Experiments were performed on laminates of glass epoxy specimens for characterization of material parameters and determination of mode-II fracture energies for different thicknesses. Effect of laminate thickness on fracture energy of transverse crack tension (TCT) and end notched flexure (ENF) specimens has been numerically studied and comparison with experimental results has been made. It is shown that the developed numerical approach is capable of estimating increase in fracture energy due to size effect.

• Coupled systems mechanics
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• v.13 no.2
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• pp.95-113
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• 2024

In this paper, we will analyse the thermo-elastic behavior of the plate element of a structure arranged in a climatically aggressive environment (extreme temperature), we use a refined four-variable thick plate theory to take the shear effect into consideration, the proposed theory less computationally expensive and more accurate so that it incorporates the shear effect into the formulation. The plate is assumed to be simply supported on its four edges, so exact (closed-form) solutions are found according to the Navier expansion, and the governing stability equations and associated boundary conditions of the problem are obtained via the virtual works principle. The plate studied ismade of laminated composite materials, so a parametric study is needed to see the effect of different types of parameters and coupling on the critical temperature value causing thermo-elastic instability of the plate and also on the natural frequency of free vibration, as well as for other parameters such as anisotropy, slenderness and aspect ratio of the plate and finally the lamination angle. Numerical results are obtained for specially orthotropic and antisymmetrical plates and are compared with those obtained by othertheoriesin the literature to validate the analysis approach used.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.10-14
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• 2002

Structural behavior of high-pressure composite vessels of TYPE 3 (full-wrapped over a seamless aluminum liner) was studied through numerical simulations based on 3D nonlinear finite element method. Under high-pressure loading, a TYPE 3 composite vessel shows material nonlinearity due to elastic-plastic deformation of aluminum liner, and mismatch of deformation at the junction of cylinder and dome causes geometrical nonlinearity. Finite element modeling and analysis technique considering this nonlinearity was presented, and a pressure vessel of 6.8L of internal volume was analyzed. Design specification to satisfy requirements was determined based on analysis results.