• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.6 no.4
• /
• pp.108-117
• /
• 1997

A continuum analysis has been performed for the application to the thermo-elasto-plastic behavior in a discontinuous metal matrix composite. an FEM (Finite Element Method) analysis was implemented to obtain the internal field quantities of composite as well as overall composite behavior and an experiment was demonstrated to compare with the numerical simulation . As the procedure, a reasonably optimized FE mesh generation, the appropriate imposition of boundary condition , and the relevant post processing such as elastoplastic thermomchanical analysis were taken into account. For the numerical illustration, an aligned axisymmetric single fiber model with temperature dependent material properties and precipitation hardening effect has been employed to assess field quantities. It was found that the residual stresses are induced substantially by the temperature drop during the thermal treatment and that the FEM results of the vertically and horizontally constrained model give a good agreement with experimental data.with non-woven carbon mat is about 24% higher than that of composite materials without non-woven carbon mat. Transverse tensile strength and torughness also increase by inserting non-woven carbon mat between layers.

• International Journal of Aeronautical and Space Sciences
• /
• v.13 no.2
• /
• pp.221-228
• /
• 2012

An active compensation method for the deformation of composite structures using additional controllable metal parts is proposed, and its feasibility is experimentally investigated in a simulated space environment. Composite specimens are tested in a vacuum chamber, which is able to maintain pressure on the order of 10-3 torr and interior temperature in the range of ${\pm}30^{\circ}C$. The displacement-measuring interferometer system, which consists of a heterodyne HeNe laser and an interferometer, is used to measure the displacement of the whole structure. Meanwhile, the strain of the composite part and temperature of both parts are measured by fiber Bragg grating sensors and thermistors, respectively. The displacement of the composite structure is maintained within a tolerance of ${\pm}1{\mu}m$ by controlling the elongation of the metal part, which is bonded to the end of the composite part. Also, the possibility of fiber Bragg grating sensors as control input sensors is successfully demonstrated using a proper corrective factor based on the specimen temperature gradient data.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.21 no.7
• /
• pp.669-673
• /
• 2008

ITO thin film was deposited on PC substrate in Facing Targets Sputtering (FTS) system with various sputtering conditions. After it is applied to external bending force, we investigated how change the surface and electrical property of as-deposited ITO thin film. As the L(face-plate distance) of substrate decreases, it found that the maximum crack density is increasing at the center position and decreasing crack density as goes to the edge. So to apply same curvature (r) and bending force to PC substrate with ITO thin film, we fixed the L that is equal to curvature radius (2r). Before bending test, ITO thin films that deposited in the input current of 0.4 A and thickness of 200 nm already had biaxial tensile failure because of each different CTE (Coefficient of Thermal Expansion) and Others had been shown no bending or crack. After bending test, all samples had been shown cracks at about 200 times and as increasing the crack density, resistivity increased.

• Journal of Powder Materials
• /
• v.23 no.3
• /
• pp.195-201
• /
• 2016

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.4
• /
• pp.135-139
• /
• 2005

In this paper, negative SU-8 photoresist processed at low temperature is characterized in terms of delamination. Based on a $3^3$ factorial designed experiment, 27 samples are fabricated, and the degree of delamination is measured for each. In addition, nine samples are fabricated for the purpose of verification. Employing the. neural network modeling technique, a process model is established, and response surfaces are generated to investigate degree of delamination associated with three process parameters: post exposure bake (PEB) temperature, PEB time, and exposure energy. From the response surfaces generated, two significant parameters associated with delamination are identified, and their effects on delamination are analyzed. Higher PEB temperature at a fixed PEB time results in a greater degree of delamination. In addition, a higher dose of exposure energy lowers the temperature at which the delamination begins and also results in a larger degree of delamination. These results identify acceptable ranges of the three process variables to avoid delamination of SU-8 film, which in turn might lead to potential defects in MEMS device fabrication.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3311-3316
• /
• 2011

New poly(arylene ether)s (PAEs) with both transparency and heat-resistance were prepared by a polycondensation of FBPODS, an ordered-sequence aromatic dihalide, and cardo typed aromatic diols containing fluorene and/or adamantane moiety and also non-cardo typed 1,5-naphthalene diol. The resulting polymers had their glass transition temperatures ranged from 202 to $247^{\circ}C$. Based on TGA data, they exhibited excellent thermal stabilities, showing 5% weight loss at $434-487^{\circ}C$. They had low thermal expansion coefficients of 58-59 ppm at temperature range of $50-200^{\circ}C$ as well as good mechanical properties with moduli of 1757-2143 MPa. The optical transmittance for the PAE films was over 70% at 550 nm, except for the PAE that contains naphthalene moiety (30% at 550 nm). They also showed water uptake of about 0.68% regardless of their chemical compositions. Therefore, the newly developed PAEs show strong potential as plastic substrates for flexible devices for display, solar cell and e-paper.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.145-148
• /
• 2006

Cold gas dynamic spray is a relatively new coating process by which coatings can be produced without significant heating during the process. Cold gas dynamic spray is conducted by powder sprayed by supersonic gas jet, and generally called the kinetic spray or cold-spray. Cold-spray was developed in Russia in the early 1980s to overcome the defect of thermal spray method. Its low process temperature can minimize thermal stress and also reduce the deformation of the substrate. Most researches on cold-spray have focused on micro scale coating, but our research team tried to apply this method to macro scale deposition. The macro scale deposition causes deformation of a thin substrate which is usually convex to the deposited side. In this research, the main cause of the deformation was investigated using 6061-T6 aluminum alloy and properties of deposited aluminum layer such as coefficient of thermal expansion, Elastic modulus, hardness, electric conductivity were measured. From the result of the analysis, it was concluded that compressive residual stress was the main reason of substrate deformation while CTE had little effect.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1459-1462
• /
• 2008

In this paper we describe solutions to address critical challenges in direct fabrication of amorphous silicon thin film transistor (TFTs) arrays for active matrix flexible displays. For all flexible substrates a manufacturable handling protocol in automated display-scale equipment is required. For metal foil substrates the principal challenges are planarization and electrical isolation, and management of stress (CTE mismatch) during TFT fabrication. For plastic substrates the principal challenge is dimensional instability management.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.373-376
• /
• 2008

New glass compositions for lead free, low temperature sealing glass frit was examined in $ZnO-V_2O_5-P_2O_5$ glass system which can be used sealing material for PDP to be made of soda lime glass substrates. Among many glass compositions, KFS-C glass showed low glass transition point (Tg) and good fluidity and adhesion characteristics when it was tested by flow button method at low temperature of $420^{\circ}C$. Its Tg was $317^{\circ}C$ and thermal expansion coefficient (CTE) was $70{\times}10^{-7}/K$. The glass frit was mixed with an organic vehicle to make a paste and it was dispensed and sealed with soda lime glass substrates at $420^{\circ}C$ for 10min. Sealed glass panels also showed good adhesion strength even sealed at low temperature of $420^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.55 no.2
• /
• pp.135-139
• /
• 2018

The glass structure and antibacterial properties of $(65-x)ZnO-xB_2O_3-35P_2O_5$ glasses were investigated. Zinc borophosphate glasses were prepared using a conventional melt-quenching technique at $1000^{\circ}C$. Glass transition temperature and CTE were studied and the structure of zinc borophosphate glasses was evaluated by FTIR. The $Zn^{2+}$ state increase with increasing ZnO content was investigated by XPS and a single sharp Zn $2P_{3/2}$ peak was confirmed, showing that Zn $2P_{3/2}$ exists as $Zn^{2+}$. In order to to evaluate the antimicrobial activity, Escherichia coli (E. coli) was used following the Japanese Industrial Standard JIS Z 2801; the E. coli death rate was found to increase with increasing $Zn^{2+}$ content of glasses.