• Composites Research
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• v.15 no.5
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• pp.44-52
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• 2002

To study numerically the mechanical behaviors of advanced composite materials considering the microscopic phenomena as well as the macroscopic properties and behaviors, a multi-scale modeling and analysis by the mathematical homogenization method with the help of the finite element method(FEM) are reviewed. The hierarchical modeling strategy and the formulation are briefly described first to give some idea of the multi-scale framework. The latter half of this article focuses on the verification of the multi-scale analysis by the homogenization method in its applications to real advanced materials. The first example is the verification of the predicted macroscopic(homogenized) properties based on the microstructure of porous ceramics. In spite of the complexity of the random microstructure, the error between the predicted and the measured values was only 1%. Next, two applications to the process simulation of fiber reinforced polymer matrix composites are presented. The permeability characteristics are evaluated for sheared weave fabrics for resin transfer molding(RTM) simulation, and the thermoforming of FRTP sheet is analyzed considering the large deformation of the knit structure during the deep-draw forming was verified by comparison with the experimental results.

• Composites Research
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• v.30 no.6
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• pp.410-415
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• 2017

This paper predicted deformation due to thermal residual stress in composites using finite element analysis. Temperature cycle, Model shape, Laminate angle, Stacking sequence, chemical shrinkage of resin, and thermal expansion are affect composite deformation. Compare the results of the analytical model with the actual model of the same shape. This paper suggests that the analytical results can be applied to actual Model.

• Korea-Australia Rheology Journal
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• v.20 no.1
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• pp.7-14
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• 2008

The objective of this work is to propose a procedure to simulate the flow in the LCM (Liquid Composites Molding) processes by finite difference discretization in a curvilinear coordinate system adapted to the shape of the saturated zone. The numerical results obtained are compared with experimental results obtained by an experimental device elaborated at our laboratory. It allows to realize linear and radial injections for different porosities and to observe the flow front kinetics. Numerical and experimental results are then compared with those of the literatures and excellent agreements are noticed. Finally, we suggest a concept of the capillary number to explain the variations of the permeability obtained for pressure values lower than 0.25 Bar.

• Proceedings of the KIEE Conference
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• 1997.07e
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• pp.1767-1769
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• 1997

In this paper, interpenetrating polymer network method was introduced in order to improve withstand voltage properties of epoxy resin. The single network structure specimen(E series), simultaneous interpenetrating polymer network specimen(EM series) and pseudo interpenetrating polymer network(EMP series) specimen were manufactured. In order to investigate influence upon electrical properties, dc, ac, and impulse voltage dielectric strength were measured. As a result, it was confirmed that electrical properties of epoxy composites can be superior as IPN introduced to it bring about firm and high density of inner structure.

• Elastomers and Composites
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• v.33 no.5
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• pp.355-362
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• 1998

The purpose of this paper is to develop a rational engineering conductive carbon filled composite through understanding of the effect of conductive carbon black. Polycabonate(PC), Acrylonitrile Butadiene Styrene copolymer(ABS) and PC/ABS resin were used as matrix of the conductive polymer composites. From the experimental results, PC filled with the fiber shaped carbon black showed a possibility to be a rational engineering conductive composite.

• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.791-796
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• 1992

SiC(p)-TiC(p) composites were prepared by gas pressure sintering technique. B4C powder and phenolic resin were added as sintering aids by 0.3 wt%-B and 3 wt%-C, TiC powder were dispersed in SiC by 0, 10, 20, 30 and 50 vol%. Flextural strength, fracture toughness and theoretical density of 70 vol% SiC-30 vol% TiC composite sintered at 220$0^{\circ}C$ by gas pressing were 540 MPa, 5.5 MPa.m1/2 and 98.8% respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1988.10a
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• pp.21-26
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• 1988

Composition with O-3 connectivity were fabricated from PZT and phenolic resin powders. These composites were investigated for dielectric and pizoelectric properties with PZT-polymer interface porosity variation. The interface porosity dependence of dielectric and piezoelectric properties was especially discussed by porosity factors. The interface porosity dependence of piezoelectric constant was larger than that of dielectric constant. It was considered that the interface pore plays the role of a stress buffer. Thus the local stress applied on PZT particles in the composite was remarkably diminish.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.529-531
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• 1999

In this Paper, the variable dielectric breakdown strengths of epoxy composites were investigated at belling absorption condition in order to observe the influences of moisture in out door use. Also. in order to improve withstand voltage properties at moisture absorbtion condition, IPN(interpenetrating polymer network) method was Introduced and the Influence was investigated. As Adding filler(SiO$_2$) classified by o(phr), 50(phr) and 100[phr] to two kinds of matrix resin, six kinds of specimens were manufactured. As a result, it was confirmed that dielectric breakdown strength wer degraded with boiling time and filer content increasing. But, it was confirmed that dielectric breakdown strength degrading rate were lowered by the Improvement of adhesion strength in IPN specimens.

• Composites Research
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• v.12 no.2
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• pp.62-69
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• 1999

During fatigue loading of composite materials, damage accumulation can be monitored by measuring their material properties. In this study, fatigue modulus is used as the damage index. Fatigue life of composite materials may be predicted analytically using damage models which are based on fatigue modulus and resultant strain. Damage models are propesed as funtions of applied stress level, number of fatigue cycle and fatigue life. The predicted life was comparable to the experimental result obtained using E-glass fiber reinforced epoxy resin materials and pultruded glass fiber reinforce polyester composites under two-stress level fatigue loading.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.22-28
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• 2000

The fiber reinforced composite materials is widely used in aircraft, space structures and robot arms because of high specific strength and high specific modulus. The on-line cure monitoring during the cure process of the composite materials has become an important research area for the better quality and productivity. In this paper, the dielectric circuit of the wheatstone bridge type for measuring the dissipation factor was designed and manufactured. Also, the dielectric sensor for the cure monitoring of the high temperature composites was developed. The residual thermal stresses of the dielectric sensor were analyzed by the finite element method and its dielectric characteristics under high temperature were evaluated. The on-line cure monitoring of the BMI resin was performed using the wheatstone bridge type circuit and developed high-temperature dielectric sensor.