• Journal of Mechanical Science and Technology
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• 제19권11호
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• pp.2025-2031
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• 2005

Eshelby type micro mechanics model with a newly developed piezoelectric Eshelby tensor is proposed for predicting the effective electroelastic properties of the piezoelectric composite. The model is applied for piezoelectric solids containing both porosities and metal inhomogeneities. The effective electroelastic moduli of the composites such as stiffness, piezoelectric constants, and dielectric constants are predicted by the present model, which are extensively compared with the existing experimental results from the literatures. The validity of Eshelby type model for predicting the effective properties of the composite is thoroughly examined. It can be concluded from this study that a new mechanism is needed to compute correctly the dielectric constants among the effective properties of the composites.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.173-182
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• 1996

An analytical model has been developed to predict the elastic properties of a filled resin reinforced by chopped fibers, a three-phase composite such as a filled sheet molding compound(SMC). In the model the matrix material and fillers form an effective matrix. The effective matrix is then considered to be reinforced with long fibers lying in the sheet plane but randomly oriented in the plane. Expressions for the resulting transversely isotropic composite properties are explicitly presented. Using this model, the Young's and shear moduli are calculated for the SMC sample with filler weight fraction of 35% and fiber content of 30%. The same properties are also determined experimentally. The agreement between the calculated and measured elastic moduli is found to be very good for the in-plane properties. However, the out-of-plane properties show a large difference because the effect of voids is not taken into account in the model.

• 한국유체기계학회 논문집
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• 제15권4호
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• pp.55-60
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• 2012

The purpose of this study is to investigate the buckling load of filament-wound composite towers for large scale wind-turbine using finite element method(FEM). To define material properties, we used both the effective property method and the stacking properties method. The effective properties method is to assume that composite consists of one ply. The stacking properties method is to assume that composite consists of some stacked plies. First, linear buckling analysis of the tower, filament-wounded with angles of [${\pm}30$] was carried out by two methods for composite material properties, the stacking method and the effective method. and FE analysis was performed for the composite towers according to filament winding angles of [${\pm}30$], [${\pm}45$], [${\pm}60$]. FE analysis results using the stacking properties of the composite were in good agreement with the results by the effective properties. The difference between FEM results by material properties methods was approximately 0~2.3% in buckling Analysis and approximately 0~0.6% in modal analysis. And above the angle of [${\pm}60$], there was a little change of buckling load.

• 한국해양공학회지
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• 제25권2호
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• pp.73-78
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• 2011

The purpose of this study was to investigate the natural frequency of filament-wound composite towers for large scale wind-turbines using the finite element method (FEM). To define the material properties, we used both the effective property method and the stacking properties method. The effective properties method assumes that a composite consists of one ply. The stacking properties method assumes that a composite consists of several stacked plies. First, a modal analysis of the tower, filament-wound with angles of $[{\pm}30]$, was carried out using the two methods for composite material properties, the stacking method and effective method. Then, an FE analysis was performed for composite towers using filament winding angles of $[{\pm}30]$, $[{\pm}45]$, and $[{\pm}60]$. The FE analysis results using the stacking properties of the composite were in good agreement with the results from the effective properties method. The difference between the FEM and material properties methods was approximately 0~0.6%

• 한국해양공학회지
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• 제25권2호
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• pp.79-84
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• 2011

The purpose of this study was to investigate the buckling load of filament-wound composite towers for large scale wind-turbines using the finite element method (FEM). To define the material properties, we used both the effective property method and stacking properties method. The effective properties method assumes that a composite consists of one ply. The stacking properties method assumes that a composite consists of several stacked plies. First, a linear buckling analysis of the tower, filament-wound with angles of $[{\pm}60]$, was carried out using the two methods for composite material properties: the stacking method and effective method. An FE analysis was also performed for the composite towers using the filament winding angles of $[{\pm}30]$, $[{\pm}45]$, and $[{\pm}60]$. The FE analysis results using the stacking properties of the composite were in good agreement with the results from the effective properties method. The difference between the FEM results and material properties method was approximately 0~2.3%. Above the angle of $[{\pm}60]$, there was little change in the buckling load.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.684-689
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• 2008

In this study, homogenization method combined with the effective interface model for the characterization of properties of the nanoparticulate composites is developed. In order to characterize particle size effect of nanocomposites, effective interface model has been developed. The application range of analytical micromechanics approach is limited because a simple analytical approach is valid only for simple and uniform geometry of fiber particles. Therefore this study focuses on the analysis of mechanical properties of the effect interface through the continuum homogenization method instead of using analytical micromechanics approach. Using the homogenization method, elastic stiffness properties of the effective interface are numerically evaluated and compared with the analytically obtained micromechanics solutions. The suggested homogenization method is expected to be applied to optimization problems for nanocomposite design.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1163-1167
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• 2003

Effective properties of ceramic matrix plain woven textile composites were calculated using finite element analysis. The considered geometry is a unit cell of plain weave and the analysis was performed by commercial finite element program, ANSYS. The materials for analysis are 3 types for matrix, 1 type for fiber with various volume fraction. The result indicates that the effective properties of ceramic matrix composites can be controlled by the volume fraction. The result can be used for numerical analysis using ceramic matrix composites.

• 한국기계가공학회지
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• 제18권12호
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• pp.28-37
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• 2019

Due to their flexible tailoring qualities, composites have become fascinating materials for structural engineers. While the research area of fiber-reinforced composite materials was previously limited to synthetic materials, natural fibers have recently become the primary research focus as the best alternative to artificial fibers. The natural fibers are eco-friendly and relatively cheaper than synthetic fibers. The main concern of current research into natural fiber-reinforced composites is the prediction and enhancement of the effective material properties. In the present work, finite element analysis is used with a numerical homogenization approach to determine the effective material properties of jute fiber-reinforced epoxy composites with various volume fractions of fiber. The finite element analysis results for the jute fiber-reinforced epoxy composite are then compared with several well-known analytical models.

• 대한기계학회논문집A
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• 제28권12호
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• pp.1950-1957
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• 2004

Analysis for structures composed of materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. In order to evaluate the effective properties, a unit cell is defined and loaded somehow, and its response is investigated. The imposed loading, however, should accord to the status of unit cells immersed in the macroscopic structure to secure the accuracy of the properties. In this study, mathematical description for the periodicity of the displacement field is derived and its direct implementation into FE models of unit cell is attempted. Conventional finite element code needs no modification, and only the boundary of unit cell should be constrained in a way that the periodicity is preserved. The proposed method is applicable to skew arrayed in-homogeneity problems. Homogenized in-plane elastic properties are evaluated for a few representative cases and the accuracy is examined.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 일렉트렛트 및 응용기술
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• pp.23-26
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• 2002

In ceramic systems using LTCC, many components including embedded passives and TRL's are used for composition of 3-dimensional circuit. So the exact analysis on this components must be performed. As for the TRL's, material properties including electrical conductivity of metal, loss factor and effective dielectric constant of dielectric material and geometrical factors like roughness of surface, vias, dimension of TRL structure have a large effect on the characteristics of transmission lines. Such properties of materials have different values in each system with ideal ones presented in text book. In this research, the effective material properties in each system are examined and the effect of material properties and geometrical factors on the characteristics of TRL's are analyzed and quantified by simulation and measurement.