• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.15-18
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• 2006

The test result of mat concrete applying both hydration heat difference and insulation curing method on new construction of Cheongju university educational building are summarized as following. Both fresh concrete and compressive strength properties were satisfied In aimed value. Setting time of concrete incorporating 15% of fly ash(FA) retarded 1.2 hour than control concrete. Temperature history of mali concrete indicated that the highest temperature of center was exhibited at $126^{\circ}C$ after 51 hours while the highest temperature of upper section was $10.6^{\circ}C$ after 46 hours. Temperature Difference between center and surface was managed at less than $6^{\circ}C$ during whole curing period. In addition the temperature of upper section secured more than $3.3^{\circ}C$ while the temperature of outside was indicated at less than $-10^{\circ}C$. Maturity by parts of construction secured more than $30^{\circ}C$ DD higher than outside at 3 days. The more number of times, applying insulation curing method by double bubble sheets, increased, the higher economic effect was secured. Overall it was clear that applying both double bubble sheets and hydration heat difference method on this new construction can resist hydration heat crack, early frost demage and strength decrease. It also significantly contributed quality improvement of cold weather concreting

• Applied Chemistry
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• v.15 no.1
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• pp.17-20
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• 2011

A disposable light exposure detector kit has been developed by UV curing of a hydrogel material. The devised light exposure detector kit consisted of light sensitive structures, bottom plate, character sheet and sticky back plate. A light exposure detector kit has a serial light sensitive structures that contain various light sensitive dyes such as rhodamine and fluorescein. The light sensitive structure composed of UV curable hydrogel polymer material as a supporing material and photosensitive dye in a certain concentration. The fabrication procedure of the ligh exposure detector kit is very simple and fast due to UV curing procedure of a photopolymerizable hydrogel material such as poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) with a photosensitive dye. By the proposed fabrication method, various size and shape of a light exposure detector kit could be fabricated using a flexible elastomer mold. Due to a fast and inexpensive fabrication method, the light exposure detector kit could be use a single use for various industrial applications. According to light irradation, the light sensitive structure on a light exposure detector kit could be lose its color by decomposition of a photosensitive dye chemical in the structure. Thus the amount of the exposed light on a substrate could easily be recognised by changing color or transparency of the structure.

• Current Research on Agriculture and Life Sciences
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• v.26
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• pp.23-30
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• 2008

In this paper, when the silk fabric was modified by ethylene cyanohydrine, the reaction mechanism between both was studied at various treatment conditions such as curing temperatures and times, ethylene cyanohydrin concentrations and $ZnCl_2$ concentrations. Through the FT-IR and DSC analyses of the treated silk fabrics, we found the results as follows : It was observed in FT-IR analysis of the treated silk fabrics that the -OH characteristic peak($3,450cm^{-1}$)position and shape were all changed when drying and curing treatment conditions were at $80^{\circ}C$ for 3 minute and $110^{\circ}C$ for 2.5 minute, and the concentration of the $ZnCl_2$ was 0.1%. It indicated that the -OH group of the silk participated in the reaction between the silk fabric and ethylene cyanohydrin. From the DSC analysis, it was found that the pyrolysis temperatures of the treated silk fabrics by ethylene cyanohydrin which was processed in the same condition, were all increased from $311^{\circ}C$ to ab. $320^{\circ}C$. From the FT-IR analyses of the silk fabrics treated by ethylene cyanohydrin at the various concentrations of $ZnCl_2$, it was found that the -OH characteristic peaks($3,450cm^{-1}$) were similar to the nontreated one except that of the fabric treated at the $ZnCl_2$ conconcentration of 0.8% when drying and curing treatment conditions were at $80^{\circ}C$ for 3minute and $110^{\circ}C$ for 2.5 minute, and the concentration of the ethylene cyanohydrin was 5%. In the case of the $ZnCl_2$ concentration of 0.8% solution, a lot of change were observed in peak. From the DSC analysis of the treated silk fabrics which was processed in the same condition, it was showed that the pyrolysis temperatures of treated silk fabric were all increased from $311^{\circ}C$ to ab. $320^{\circ}C$, which was no relation with the concentration of $ZnCl_2$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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• pp.116-127
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• 2014

The studies were carried out to process one cycle for a day to the large section tunnel lining concrete. Climatic characteristics of the tunnel inside are changed, when the temperature of the concrete placement is low, the mold remove time is increased that the heat of hydration speed be delayed because affects the strength development, to compensate for this, after installing the curing sheet on both sides of the steel form and installation of tunnel entrance, when it comes to providing the additional heat source of $28{\pm}2^{\circ}C$ therein, it was to be achieved early strength development control standards (4.5MPa) presented as a crack control scheme or more, thus, It was able to remove after age of 14hr from mold. On the other hand, under the conditions of $10{\pm}1^{\circ}C$ that a natural curing temperature in the tunnel, it was analyzed must ensure the curing time of 36hr or more after concrete placement. Throughout this study, the concrete strength development and the temperature in the early-age concrete, it can find that reverify the curing temperature is greatly affected, even concrete fly ash is mixed 10%, if it is possible to raise the surface temperature for a predetermined time, is not a problem in the early strength development.

• Composites Research
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• v.30 no.1
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• pp.65-70
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• 2017

Carbon fiber reinforced composites have light weight and high mechanical properties. These materials are only applicable in limited shape structure cause by complex curing process and low drapability. To solve this problem, Long Fiber Prepreg Sheet (LFPS) has been proposed. In this research, electric device cover plate was selected and designed by using LFPS. Before the design process, we analyzed the target structure to which the rib structures were applied. And 8-inch tablet PC product was selected. For FE analysis, simple loading and boundary conditions were applied. Stiffness of rib structure was investigated according to the rib pattern and shape changes. Rib pattern and shape were selected based on fixed volume condition analysis results. And uneven rib width model was selected for the best case whose deflection was reduced 6~10% than uniform rib model.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.238-239
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• 2017

Waterproofing is a very important process in terms of durability of buildings. The materials used for waterproofing work to protect the concrete structure from external deterioration factors. In particular, the waterproofing materials applied to the exterior of the concrete structure have various problems due to changes in the external environment and variables in the construction process. The waterproof layer is repeatedly dried and shrunk according to changes in the external moisture environment, and the surface may be deteriorated due to exposure to long-term sunlight. In the case of the roof waterproofing in the structure, the waterproof layer which does not have a sufficient curing period shows much swelling and floating phenomenon. These defects, such as swelling and lifting, account for most of the defects that occur in the waterproof layer of the concrete slabs. Generally, it is difficult to expect the same level of performance as the initial state even if the waterproofing work is repaired when a defect occurs. Therefore, it is possible to reduce the defects of the waterproof layer such as swelling and lifting by forming a waterproof layer which can be integrated with the concrete surface by using a polyurethane type waterproofing material having a relatively low defective ratio compared to other waterproofing materials. So in this study, the basic properties of polyurethane waterproof sheet reinforced with non-woven fabric are investigated in order to understand field applicability.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.622-627
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• 2009

Using an alkali-solution developable photosensitive resin and a carbon black as a conductive filler, photo-patternable pastes for polymer thick film resistor were fabricated and evaluated. A photo solder resist (PSR), which is usually used as protecting layer of printed circuit board (PCB), was used as a photosensitive resin so that ultraviolet exposure and alkali-aqueous solution development of paste were possible. After fabricating the photosensitive polymer resistor paste, the electrical properties of thick film resistors were measured using PCB test boards. Sheet resistance was decreased with increasing amount of carbon black, but the developability was limited in excess loading of carbon black. The sheet resistance was also reduced by re-curing and the change rate was smaller in higher carbon black loading. Moreover, finely patterned meander-type thick film resistors were fabricated using photo-process and large resistance up to several tens of sheet resistance could be obtained in small area by this technique.

• Design & Manufacturing
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• v.14 no.4
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• pp.65-70
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• 2020

Partial reinforcement of sheet metal parts with CFRP patch is a technology that can realize ultra-lightweight body parts while overcoming the high material cost of carbon fiber. Performing these patchworks with highly productive press equipment solves another issue of CFRP: high process costs. The A-pillar is the main body part and has an undercut shape for fastening with other parts such as roof panels and doors. Therefore, it is difficult to bond CFRP patches to the A-pillar with a general press forming tool. In this paper, a flexible system that applies uniform pressure to complex shapes using ceramic particles and silicone rubber is proposed. By benchmarking various A-pillars, a reference model with an undercut shape was designed, and the system was configured to realize a uniform pressure distribution in the model. The ceramic spherical particles failed to realize the uniform distribution of high pressure due to their high hardness and point contact characteristics, which caused damage to the CFRP patch. Compression equipment made of silicone rubber was able to achieve the required pressure level for curing the epoxy. Non-adhesion defects between the metal and the CFRP patch were confirmed in the area where the bending deformation occurred. This defect could be eliminated by optimizing the process conditions suitable for the newly developed flexible system.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.627-632
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• 1998

This study deals with the effect on adhesive strength properties of waterproofing and reinforcing layer and mortar or concrete substrate applicated by epoxy resin anticorrosive and bonding materials. Properties of adhesive strength change condition of concrete substrate, temperature, moisture, curing and cleaning and so on. The purpose of this study is that it makes the estimation value of bond strength of concrete wall and epoxy resin layer when coated epoxy resin as anticorrosive materials for durability performance estimation depend on concrete watertightness, and when penetrated epoxy resin for the reinforcement of concrete used the carbon fiber sheet.

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.92-102
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• 1996

In this research, to develope the A1 7075/CFRP multilayered hybrid composites, CRALL(Carbon Reinforced aluminum lamiate) specimens were processed by autoclavecuring system that curing temperature, time, surface pretreatment condition of aluminum were constant. Andthe fatigye life and failure mechanism on CFRP volume fraction and fiber orientation of CRALLspecimens were investigated. A fatigue life was greatly influenced by effect of CFRP fiber volume fraction but it was less effected than those of fiber orientation. The fatigue failure arised from interface delamination of CFRP and aluminum sheet after shear fracture of aluminum layer. The failure mechanism is assumed that the aluminum laminates which divide the CFRP into many thim layers tend to arrest the failure propagation.