• Journal of the Korean Ceramic Society
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• v.41 no.5
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• pp.349-352
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• 2004

Organic-inorganic hybrid sol based on ZrO$_2$-SiO$_2$ system was prepared by sol-gel process. Firstly, ZrO$_2$ non-aqueous precursor sol was synthesized and then organosilane compounds which include epoxy silane (GPTS; 3-g1ycidoxypropyl tri-methoxysilane) and acryl silane (ACS; (3-(tri-methoxysilyl)propylmethacrylate)) were added to ZrO$_2$precursor sol for hybridization. Finally, com-mercial silica sol was added to improve the mechanical properties. Synthesized organic-inorganic Zr-hybrid sol was coated on polycarbonate substrate for enhancing it’s mechanical properties, especially hardness. Vicker’s hardness of polycarbonate sub strate was increased from 13.6 to 17.8 MPa and its pencil hardness was increased from 2 to 7 H, respectively, after coating and drying at 10$0^{\circ}C$ for 30 min.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.2
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• pp.1-12
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• 1999

Brown oxide and/or black oxide layers were formed on the surface of Cu-based leadframe by chemical oxidation of leadframe in hot alkaline solutions, and their growth characteristics were studied. Then, to measure the adhesion strength between leadframe and epoxy molding compound (EMC), oxidized leadframe samples were molded with EMC and machined to form sandwiched double-cantilever beam (SDCB) specimens and pull-out specimens, respectively. Results showed that the adhesion strength of un-oxidized leadframe/EMC interface was inherently very poor but could be increased drastically with the nucleation of acicular CuO precipitates on the surface of leadframe. The presence of smooth faceted $Cu_2O $ on the surfaces of leadframe gave close to zero interfacial fracture toughness (Gc) and reasonable pull strength (PS). A direct correlation between Gc and PS showed that PS can be a measure of Gc only in a limited range.

• Journal of Adhesion and Interface
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• v.11 no.2
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• pp.41-49
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• 2010

Furan-containing epoxide monomers (8, 9) were designed and synthesized as carbon-neutral, environment-friendly adhesion material. Bicyclic skeleton were constructed using the Diels-Alder reaction of furan and methyl acrylate, both readily accessible starting material from a biomass via bio-refinery process. After reduction of ester functionality, resulting hydroxyl moieties were coupled to epichlorohydrin to provide the epoxy-functionalized furanic monomers (8, 9). The structure of new furanic monomers was confirmed by $^1H$ and $^{13}C$ NMR spectroscopy. As UV-curable monomers, basic properties such as UV curing time and the extent of UV curing were evaluated by photo DSC. Photo-curing shrinkages were measured by linear variable differential transformer transducer (LVDT) and the effect of molecular structure on shrinkage was considered. In addition, new synthetic compounds showed the shear strength over 3 MPa when they were photo-cured between polycarbonate plates, which indicates these compounds are feasible to use as photo-curable adhesive materials.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.57-60
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• 2002

The stiffness model has been proposed to predict elastic constants of twisted yarn composites. The model is based upon the unit cell structure, the coordinate transformation, and the volume averaging of compliance constants for constituent materials. For the correlation of analytic results with experiments, composite samples of various yarn twist angle were tested. The samples were fabricated by the RTM process using glass yarns and epoxy resin. The correlations of elastic constants showed relatively good agreements. The model provides the predictions of the three-dimensional engineering constants, which are valuable input data for the analytic characterization of textile composites made of twisted yarn.

• 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 IEEK Conference
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• 2006.06a
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• pp.597-598
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• 2006

This paper describes a development of a new $1.4{\times}1.1$ and $2.0{\times}1.4mm$ RF SAW filters made by PCB substrate instead of HTCC package, and this technology can reduce the cost of materials down to 40%. We have investigated the multi-layered PCB substrate structures and raw materials to find out the optimal flip-bonding condition between the $LiTaO_3$ wafer and PCB substrates. Also the optimal materials and processing conditions of epoxy laminating film were found out through the experiments which can reduce the bending moment caused by the difference of the thermal expansion between the PCB substrate and laminating film. The new PCB SAW filter shows good electrical and reliability performances with respect to the present SAW filters.

• Advanced Composite Materials
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• v.17 no.4
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• pp.373-407
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• 2008

This paper will examine the possibilities of the virtual tests of composite structures by simulating mechanical behaviors by using supercomputing technologies, which have now become easily available and powerful but relatively inexpensive. We will describe mainly the applications of large-scale finite element analysis using the direct numerical simulation (DNS), which describes composite material properties considering individual constituent properties. DNS approach is based on the full microscopic concepts, which can provide detailed information about the local interaction between the constituents and micro-failure mechanisms by separate modeling of each constituent. Various composite materials such as metal matrix composites (MMCs), active fiber composites (AFCs), boron/epoxy cross-ply laminates and 3-D orthogonal woven composites are selected as verification examples of DNS. The effective elastic moduli and impact structural characteristics of the composites are determined using the DNS models. These DNS models can also give the global and local information about deformations and influences of high local in-plane and interlaminar stresses induced by transverse impact loading at a microscopic level inside the materials. Furthermore, the multi-scale models based on DNS concepts considering microscopic and macroscopic structures simultaneously are also developed and a numerical low-velocity impact simulation is performed using these multi-scale DNS models. Through these various applications of DNS models, it can be shown that the DNS approach can provide insights of various structural behaviors of composite structures.

• Journal of Conservation Science
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• v.26 no.2
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• pp.183-190
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• 2010

We fabricated urethane material based on properties of reversible and unfading for antic-ceramics restoration. This material with low viscosity was made hardness control possible that user want. And it have very strong adhesion and shear strength properties and is shown the best properties for pigment filling, anti-contractibility, coloring as like epoxy system materials. Particularly, the yellowing and ir-reversibility problem in epoxy restoration material were finally solved. So, there is guarantee in the eternity and stabilization of restoration for antic-celamics. And in order to show the reversible state of the restoration, we successfully dissolve this urethane materials in solvent after perfect restoring subsequently.

• Journal of the Korea Furniture Society
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• v.27 no.1
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• pp.8-14
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• 2016

Increasing concerns of environment need to make change furniture field to more environmentally friendly approach, such as reuse of by-products from wooden products. As it is, the methods of recycling wood for industrial purposes have the advantage of productivity and adaptability. However, the industrial way is required a certain production facility of processing wooden by-products and has possible hygienic problems due to contaminated sources. Many designers have developed their own methods for reuse of wood in unique and artistic ways. Even so, because of confined sources, it could be not enough supply. Therefore, I developed the design methodology utilizing wooden by-products from S Design Company to relieve former ways' problems. The design suggestion took materials from a safe and abundant source. The wooden leftover pieces were connected together with epoxy clay, so previous process traces of furniture are remained as a decorative factor. Moreover, the synthesized material was able to be processed by ordinary woodworking facilities without additional installations. In doing so, console table focused on a commercial purpose and dining table for an artistic objective were successfully fabricated as final suggestions. In consideration of the proposal using wooden furniture leftovers, diverse recycling designs should be investigated for future reference.

• Polymer(Korea)
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• v.36 no.5
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• pp.612-616
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• 2012

In this work, the effect of chemical treatments of multi-walled carbon nanotubes (MWNTs) on the mechanical interfacial properties of carbon fiber fabric-reinforced composites was investigated. The surface properties of the MWNTs were determined by acid and base values, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The mechanical interfacial properties of the composites were assessed by interlaminar shear stress (ILSS) and critical stress intensity factor ($K_{IC}$). The chemical treatments based on acid and base reactions led to a significant change of surface characteristics of the MWNTs, especially A-MWNTs/carbon fibers/epoxy composites had higher mechanical properties than those of B-MWNTs and non-treated MWNTs/carbon fibers/epoxy composites. These results were probably due to the improvement of interfacial bonding strength, resulting from the acid-base interaction and hydrogen bonding between the epoxy resins and the MWNT fillers.