• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.390-394
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• 2004

This is the study on dry sliding wear behavior of unidirectional carbon fiber reinforced epoxy matrix composite at ambient temperature. The wear rates and friction coefficients against the stainless steel counterpart specularly processed were experimentally determined and the resulting wear mechanisms were microscopically observed. Three principal sliding directions relative to the dominant fiber orientation in the composite were selected. Wren sliding took place against smooth and hard counterpart, the highest wear resistance and the lowest friction coefficient were observed in the antiparallel direction. When the velocity between the composite and the counterpart went up, the wear rate increased. The fiber destruction and cracking caused fiber bending on the contact surface, which was discovered to be dominant wear mechanism.

• Journal of the Korean Institute of Gas
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• v.17 no.6
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• pp.46-51
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• 2013

Composite cylinder is used by hydrogen fuel cell vehicles and natural gas vehicles because of high specific modulus, specific strength and fatigue resistance. composite cylinder has a seamless integrated liner and it is fully overwrapped with structural fibers of high strength carbon fibers in an epoxy matrix. In this study, filament winding pattern and autofrettage pressure design technique are presented considering structural weakness of knuckle and compressive residual stress. Presented methodology is verified by pressure cycling test of composite cylinders.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.21-27
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• 2001

Epoxy/BaTiO$_3$composite film type capacitors with excellent stability at room temperature, uniform thickness, and electrical properties over a large area were successfully fabricated. We fabricated composite capacitor films with good film formation capability and easy process ability, from ACF-resin as a matrix and two kinds of BaTiO$_3$powders as fillers to increase the dielectric constant of the composite film. The crystal structure of the powders and its effects on dielectric constant of the films were investigated by X-ray diffraction. DSC and dielectric properties tests were conducted to decide the right curing temperature and the optimum amount of the curing agent. As a result, the capacitors of $7{\mu}{\textrm}{m}$ thick film with 10nF/cm2 and low leakage current were successfully demonstrated.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.99.1-99.1
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• 2016

The materials for an electronic packaging provide diverse important functions including electrical contact to transfer signals from devices, isolation to protect from the environment and a path for heat conduction away from the devices. The packaging materials composed of metals, ceramics, polymers or combinations are crucial to the device operating properly and reliably. The demand of effective charge and heat transfer continuous to be challenge for the high-speed and high-power devices. Nanomaterials including graphene, carbon nanotube and boron nitride, have been designed for the purpose of exploiting the high thermal, electrical and mechanical properties by combining in the matrix of metal or polymer. In addition, considering the inherent electrical and surface properties of graphene, it is expected that graphene would be a good candidate for the surface layer of a template in the electroforming process. In this talk, I will present recent our on-going works in nanomaterials for microelectronic packaging: 1) porous graphene/Cu for heat dissipations, 2) carbon-metal composites for interconnects and 3) nanomaterials-epoxy composites as a thermal interface materials for electronic packaging.

• Journal of Power System Engineering
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• v.9 no.2
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• pp.57-64
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• 2005

This paper is the study on dry sliding wear behavior of carbon fiber reinforced epoxy matrix composites against lay-up orientation. Tests were investigated on the effect of the lay-up orientation, fiber sliding direction, load and sliding velocity when circumstance keep continuously at $21^{\circ}C$, 60%RH. Pin-on-disk dry sliding wear tests for each experimental condition were carried out with a carbon fiber reinforced plastic pin on stainless steel disk in order to search the friction and wear characteristics. The wear rates and friction coefficients against the stainless steel counterpart were experimentally determined and the wear mechanisms were microscopically observed. The effect on friction and wear behavior are observed differently, according to various conditions. When sliding took place against counterpart, the highest wear resistance and the lowest friction coefficient were observed in the $[0]_{24s}$ lay-up orientation at anti-parallel direction.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.122-125
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• 2001

The objective of this research is to develop hybridized yarns for thermoplastic composites, and to examine tile effect of cooling rate on mechanical properties of the composites. The co-braided yarn utilizing carbon fibers as reinforcements and Nylon 66 fibers as matrix materials has been fabricated. Thermoplastic composites have been manufactured by the hot-press forming process. For the processing conditions, cooling rates of $-2.5^{\circ}C$/min and $-60^{\circ}C$/min have been considered. Three-point bending test and losipescu shear test were performed to investigate the effect of the cooling rate and the surface treatment of carbon fibers. SEM photographs were used to investigate the fracture surfaces of the tested samples. The cooling rate of $-60^{\circ}C$/min resulted in the higher strength and elastic modulus for bending and shear tests. The composites of the epoxy-sized carbon fibers showed the lowest strength due to the degradation of the sizing material during the thermoforming process.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.64-69
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• 2001

In general, laminate effective orthotropic thermal conductivities are dependent on fiber and matrix material properties, fiber volume fraction and fabric geometric parameters. This paper deals with the predicting method of the transverse and the in-plane thermal conductivities of plain weave fabric composites based on the three dimensional series-parallel thermal resistance network. Thermal resistance network was applied to unit cell model that characterizes the periodically repeated pattern of plain weave. Also, an experiment apparatus is setup to measure the thermal conductivities of composite material. The numerical and experimental results of carbon/epoxy plain weave are compared.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.9-12
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• 2005

Recently, research on the morphing wing is an interesting issue to develop the capability of the wing such as improving the lift and reduction of drag during the operation of an aircraft by changing the wing shape from one configuration to another. A more efficient weight reduction of the wing using smart or morphing wing concept can be achieved in comparison with the conventional flaps. In this study, it is investigated the behaviors of the morphing wing using Macro Fiber Composite (MFC) actuators. Generally, MFC is the piezocomposite actuator with the rectangular PZT fiber and epoxy matrix, and uses the interdigitated electrode to produce more powerful actuation in the in-plane direction. Furthermore, it can produce the twisting actuation as compared with the traditional PZT actuators. In the formulation, the first-order shear deformation plate theory is used, and finite element method is adopted in the numerical analysis of the model. Results show the characteristics of the static behavior of the morphing wing according to the change of the actuation voltage.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.6
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• pp.483-495
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• 2008

The paper presents a numerical study to evaluate the phase velocities and attenuations of the average longitudinal and shear ultrasonic waves resulting from multiple scattering in fiber-reinforced composites. A computational procedure developed in this work is first used to produce a random, yet largely even distribution of fibers. Both the viscoelastic epoxy matrix and lossless randomly distributed graphite fibers are modeled using the mass-spring-dashpot lattice model, with no damping for the latter. By numerically simulating ultrasonic through-transmission tests using this direct model of composites, phase velocities and attenuations of the longitudinal and shear waves through the composite are found as functions of frequency or fiber concentration. The numerical results are observed to generally agree with the corresponding results in the literature. Discrepancies found in some detail aspects, particularly in the attenuation results, are also addressed.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.149-149
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• 2003

This paper presents the work peformed in a program developing composite material which properties satisfy structural and thermal requirements for aircrafts and spacecrafts. In the aerospace vehicle structures, the specific strength of the materials is one of the important requirements and this is why polymer matrix composite material with reinforced carbon fiber is widely used. However, the mechanical properties of the composite material have been known to be dependent on processing and this difficulties in evaluation have caused a lot of mechanical tests for each batch.