• Composites Research
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• v.22 no.5
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• pp.15-23
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• 2009

The lubricant tribological characteristics of $Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) fabricated by squeeze casting method was investigated using a pin-on-disk wear tester. The wear tests of the MMCs were performed according to fiber/particle hybrid ratio in the planar-random (PR) and normal (N) orientations sliding against a counter steel disk at a fixed speed and $25\;kg_f$ loading under different sliding distances and temperatures. The test results showed that the wear behavior of MMCs varied with fiber orientation and hybrid ratio. At room temperature, the lubricant wear behavior of F20P0 unhybrid PR-MMCs was superior to that of N-MMCs while the hybrid composites exhibited the reverse lubricant wear behavior. It was also revealed that the wear resistance of PR-MMCs was superior to that of the N-MMCs due to the joint action of reinforcements and lubricant film between the friction surfaces at an elevated temperature of $100^{\circ}C$ for both fiber only and hybrid cases. In case of $150^{\circ}C$, although the trend of weight loss was similar to that of others, the wear resistance of PR-MMCs was better than that of N-MMCs for hybrid MMCs.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.4
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• pp.327-337
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• 2012

The object of this study was to find out the effect of various reinforcing materials including Quarts Splint$^{TM}$ Mesh on the transverse strength of the denture resin. QC-20 and Lucitone199$^{(R)}$ were used as the denture resin, and polyethylene fiber Ribbond$^{(R)}$, light curing quarts fiber Quarts Splint$^{TM}$ Mesh, metal mesh were used as the reinforcing materials. Ten specimens were fabricated for each group and the size of specimens was $2.0{\times}10.0{\times}65.0mm$. To compare the effect of resin thickness, additional specimens of $2.5{\times}10.0{\times}65.0mm$, $3.0{\times}10.0{\times}65.0mm$ were fabricated. In the control group, the transverse strength of Lucitone199$^{(R)}$ was significantly higher than that of QC-20(p<0.05). Among the specimens of 2.0 mm thickness fabricated with $Lucitone199^{(R)}$ and QC-20, they showed high transverse strength in the order of metal mesh, Quarts Splint$^{TM}$ Mesh, Ribbond$^{(R)}$, and control group. In the specimens of 2.0 mm, 2.5 mm thickness, the transverse strength of Quarts Splint$^{TM}$ Mesh were significantly higher than that of QC-20(p<0.05). But in the specimens of 3.0 mm thickness, there was no significant difference.

• Conservation Science in Museum
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• v.29
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• pp.33-46
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• 2023

Modern and contemporary cultural assets are defined as a collective term for tangible historical and cultural assets produced in the modern and contemporary period (around the opening of Joseon to the present) in Korea. Among them, rickshaws have been used as a major means of transportation for about 40 years since the opening of the ports in Joseon. The repair process for rickshaws divides the rickshaw into three parts, namely the body, the cover, and the wheels, applying a plaster treatment process by referring to the outcomes of the condition assessment and material analysis for the metal, wood, fiber, and paint used. Overall, the repair process is carried out through dry/wet cleaning, joining, stabilization, reinforcement of damaged parts, and other restoration treatments, which reveal metal decorations and patterns on the scaffolding (flowers, arabesque patterns, etc.) that were previously not observable with the naked eye, while also adding to the stability of the artifact. In addition, props were produced to ensure the artifact's safe exhibition.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.3
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• pp.288-298
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• 2001

There has been a growing interest in thick composite materials especially for primary structures. Fiber waviness is one of the manufacturing defects frequently encountered in thick composite structures and affects the mechanical properties such as stiffness and strength significantly. Therefore, nondestructive evaluation technique that can detect fiber waviness of thick composite is very important for the integrity of structures. In this study, efforts were made to understand ultrasonic wave propagation in thick composites with uniform fiber waviness by adopting the ray and plane wave theories. Both theoretical and experimental investigations were conducted to understand the wave propagation in thick composites with uniform fiber waviness. The experiments were conducted on specially fabricated thick composite specimens with various degrees of uniform fiber waviness using the conventional through-transmission method to verify the predicted results. The experimental results showed good agreement with the theoretical predictions.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.453-456
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• 2009

Impact resistance of shape memory alloy hybrid composite(SMAHC) plates were experimentally investigated. Shape memory alloy(SMA) have large failure strain and failure stress and can absorb large strain energies through phase transformation. SMA wires were embedded in composite plates to improve their weak impact resistance. Tensile tests of SMA wires were performed at various temperature to investigate their thermo-mechanical properties. Low-Velocity impact tests of several types of composite plates with SMA/Al/Fe were performed. Embedding SMA wires was most effective to improve impact resistance of composite plates. The effects of SMA position on impact resistance were also investigated.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.894-899
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• 2012

In recent years, recycling process has come to be necessary for separating metals, glass fibers and polymer from WPCBs (waste printed circuit boards) due to an increasing amount of electronic device waste. In this study, dimethylformamide (DMF) and attrition mill reactor were used to separate the component such as metals, glass fiber and epoxy resin from WPCBs. Separation of glass fiber from WPCBs was carried out under stirring rates 300~600 revolution per minute (rpm) for 1~2 h as the various agitator. The recycled glass fibers (RGF) were analyzed by thermogravimetric analyzer (TGA) for degree of separation of epoxy resin in the WPCBs. The degree of separation of epoxy resin of WPCBs increased in attrition mill agitator as a mechanochemical process for recycling WPCBs. The RGF separated in the WPCBs was applied as a reinforcement in the RGF/unsaturated polyester composites to reuse as a reinforcement.

• 보존과학연구
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• s.35
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• pp.121-127
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• 2014

The Vietnam homecoming box that has been collected in National Museum of Korean The Vietnam homecoming box that has been collected in National Museum of Korean Contemporary History got severely damaged such as rot, attached foreign substance, fading, color, wood decay. In particular, the bottom of the box was unstable state that deteriorated by pests and the left strut was severely damaged by some deep cracks and pests. The metal bands were remained on the side and bottom of the box, and all the bands were seriously corroded. On the bottom-right of the lid, black foreign matter was adhered to the surface. In the process of conservation treatments, the cleaning, filling cracks, reinforcing the bottom of the box, attaching the metal bands were proceed in order after the investigation of the state.

• Polymer(Korea)
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• v.33 no.6
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• pp.620-624
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• 2009

Biomedical metal implants have been used clinically for replacement, restoration, or improvement of injury bodies based on high mechanical properties, but it has some risks such as the inflammatory, late thrombosis, or restenosis due to the low biocompatibility and toxicity. In various techniques of surface treatment developed to preserve these drawbacks, this study examined the electrospray coating technology with biodegradable poly (lactic-co-glycoic acid) (PLGA) on metal surface. Based on fundamental examination of electrospraying and solution parameters, the surface morphology of coated film was closely related to the boiling point of solvent, in-flight distance, and droplet size. The thickness of polymer film was linearly proportional to the emerged volume. This result exhibits that the polymeric droplets were continuously deposited on the polymer film. Therefore, the electrospray coating technology might be applied into the fabrication of single/multi-layered polymer film in nano-/micro-thickness and the control of the topology for biomedical metal implants including stents.

• Composites Research
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• v.33 no.5
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• pp.296-301
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• 2020

Laminated composite materials have excellent in-plane properties, but are vulnerable in thickness directions, making it easy to delamination when bending and torsion loads are applied. Thickness directional reinforcement methods of composite materials that delay delamination include Z-pinning, Stitching, Tufting, etc., and typically Z-pinning and Stitching method are commonly used. The Z-pinning is reinforcement method by inserting metal or carbon pin in the thickness direction of prepreg, and the conventional stitching process is a method of reinforcing the mechanical properties in the thickness direction by intersecting the upper and lower fibers on the preform. In this paper, I-fiber stitching method, which complement and improve weakness of Z-pinning and Stitching method, was proposed, and the static strength of composite single-lap joints using I-fiber stitching process were evaluated. The single-lap joints were fabricated by a co-curing method using an autoclave vacuum bag process. The thickness of the composite adherend was fixed, and 5 types of specimens were manufactured with varying the stitching pattern (5×5, 7×7) and angle (0°, 45°). From the test, the failure load of the specimen reinforced by the I-fiber stitching process was increased by up to 143% compared to that of specimen without reinforcement.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.382-388
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• 2010

This paper describes the standardized finite element model for carbody structures of railway vehicle made of sandwich composites. Recently, sandwich composites were widely used to railway vehicle due to the improvement of energy efficiency, high specific stiffness and strength, weight reduction and space saving in korea. Therefore, structural integrity should be verified using finite element analysis prior to the manufacture of composite railway vehicle. The standardized finite element model for composite carbody structures was introduced through comparing the results of real structural test under vertical, compressive, twisting load and natural frequency test of various railway vehicles in this study. The results show that the quadratic shell element is suitable to model the reinforced metal frame used to improve the flexural stiffness of sandwich panel compared to beam element, and layered shell and solid element are recommended to model the skin and honeycomb core of sandwich panel compared to sandwich shell element. Also, the proposed standard finite element model has the merit of being applied to crashworthiness problem without modifications of finite element model.