• International Journal of Precision Engineering and Manufacturing
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• 제8권4호
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• pp.38-44
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• 2007

Combat vehicles are frequently maneuvered in battlefields when the lives of combatants are being threatened. These vehicles are important elements that influence the consequences of a battle. Their armor must be lightweight and provide excellent protection to ensure successful operations. Ceramic composite armor has recently been developed by many countries to fulfill these requirements. We reviewed previous research to determine an effective armor design, and then fabricated a composite armor structure using $Al_2O_3$ and glass fiber-reinforced polymer. Specimens were manufactured under controlled conditions using different backing plate thicknesses and bonding methods for the ceramic layer and the backing plate. The penetration of an armor-piercing bullet was evaluated from ballistic protection tests. The bonding method between the ceramic layer and the fiber-reinforced polymer influenced the ballistic protection performance. A bonding layer using rubber provided the best protection.

• 한국세라믹학회지
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• 제30권2호
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• pp.139-147
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• 1993

Two sheets of high strength cement paste using ordinary Portland cement and water soluble polymer (polyacrylamide) were made by kneading with a twin roll mill. A carbon fiber layer out between two sheet of the cement paste, and then carbon fiber reinforced high strength cement composites were prepared by pressing them. The mechanical properties of the composites were investigated through the observation of the microstructure and the application of fracture mechanics. When the carbon fiber was added with 0.2 and 0.3wt% to the composites the flexural strength and Young's modulus were about 110∼116MPa and 74∼77GPa respectively, and critical stress intensity was about 3.14MPam1/2. It can be considered that the strength improvement of high strength cement fiber composites may be due to the removal of macropores and the increase of various fracture toughness effects; grain bridging, frictional interlocking, polymer fibril bridging and fiber bridging.

• 한국세라믹학회지
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• 제42권12호
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• pp.842-845
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• 2005

Glass composites containing ceramic fiber have been developed for Solid Oxide Fuel Cell (SOFC) seals. Effect of glass type, loading pressure and thermal cycle the leak rates of composite seals was investigated. Seal performance of two commercial glasses was compared with that of $SiO_2BaO-B_2O_3$ glass synthesized in this work. The leak rate for seals made of pyrex(R) increases from $\~0.0005\;to\;\~0.004sccm/cm$ as the gas pressure increases from 10 to 50 kPa. The soda lime silicate glass seal shows the leak rate two times higher than the one made of pyrex(R) or $SiO_2BaO-B_2O_3$ glass. The viscosity of glass at the seal test temperature is presumed to affect the leak rate of the glass seal. As the applied loading pressure increases from 0.4 to 0.8 MPa at $750^{\circ}C$, the leak rate decreases from 0.038 to 0.024 sccm/cm for composite seals. It has been found that during 50 thermal cycles between $450^{\circ}C\;to\;700^{\circ}C$ leak rates remained almost constant, ranging from 0.025 to 0.03sccm/cm. The results showed an excellent thermal cycle stability as well as sealability of the glass matrix ceramic fiber composite seals.

• 한국재료학회지
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• 제34권3호
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• pp.175-183
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• 2024

Geopolymer, also known as alkali aluminum silicate, is used as a substitute for Portland cement, and it is also used as a binder because of its good adhesive properties and heat resistance. Since Davidovits developed Geopolymer matrix composites (GMCs) based on the binder properties of geopolymer, they have been utilized as flame exhaust ducts and aircraft fire protection materials. Geopolymer structures are formed through hydrolysis and dehydration reactions, and their physical properties can be influenced by reaction conditions such as concentration, reaction time, and temperature. The aim of this study is to examine the effects of silica size and aging time on the mechanical properties of composites. Commercial water glass and kaolin were used to synthesize geopolymers, and two types of silica powder were added to increase the silicon content. Using carbon fiber mats, a fiber-reinforced composite material was fabricated using the hand lay-up method. Spectroscopy was used to confirm polymerization, aging effects, and heat treatment, and composite materials were used to measure flexural strength. As a result, it was confirmed that the longer time aging and use of nano-sized silica particles were helpful in improving the mechanical properties of the geopolymer matrix composite.

• 한국세라믹학회지
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• 제39권12호
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• pp.1158-1163
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• 2002

2차 비선형 광특성을 유도하기 위한 UV 폴링용 Ge와 B가 첨가된 광민감성 광섬유를 제조하였다. 248 nm KrF 엑시머 레이저 조사에 의하여 수소처리 없이 장주기 격자를 형성할 수 있었다. 116 mJ/$cm^2$의 펄스 에너지와 10 Hz의 조사 빈도로 1분간 광민감성 광섬유에 레이저를 조사할 경우 -4 dB의 큰 band rejection 특성을 얻을 수 있었다. 제조된 광섬유의 광민감성은 장주기 격자쌍 방법을 이용하여 측정하였으며, 8.67 kJ/$cm^2$의 fluence로 KrF 엑시머 레이저를 조사할 경우 3.3${\times}10^{-3}$의 큰 코어 굴절률 변화를 얻었다. 또한 UV 폴링 시에 광섬유 코어에 고전압을 쉽게 인가할 수 있는 H자 형상의 광섬유를 인출조건의 최적호를 통하여 제조하였다.

• 한국세라믹학회지
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• 제53권6호
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• pp.610-614
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• 2016

Tyranno SA (SiC-polycrystalline fiber, Ube Industries Ltd.) shows excellent heat-resistance up to $2000^{\circ}C$ with relatively high mechanical strength. This fiber is produced by the conversion process from a raw material (amorphous Si-Al-C-O fiber) into SiC-polycrystalline fiber at very high temperatures over $1500^{\circ}C$ in argon. In this conversion process, the degradation reaction of the amorphous Si-Al-C-O fiber accompanied by a release of CO gas for obtaining a stoichiometric composition and the subsequent sintering of the degraded fiber proceed. Furthermore, vaporization of gaseous SiO, phase transformation and active diffusion of the components of the Si-Al-C-O fiber competitively occur. Of these changes, vaporization of the gaseous SiO during the conversion process results in an abnormal SiC-grain growth and also leads to the non-stoichiometric composition. However, using a modified Si-Al-C-O fiber with an oxygen-rich surface, vaporization of the gaseous SiO was effectively prevented, and then consequently a nearly stoichiometric SiC composition could be obtained.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.176-183
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• 2007

An experimental study was performed to investigate the effects of mixing quality, inlet pressure, nozzle diameter on CO emission and radiation characteristics in porous ceramic fiber radiant burners. Observations of combustion characteristics occurring inside the burner system which was insulated fiber mat, were investigated by measuring temperature, CO emission and radiation characteristics. Combustion was achieved at the firing rate of $88{\sim}99$ kcal/hr, inlet pressure of $100{\sim}250$mm$H_2O$. CO emissions were found to be strongly dependent on the operating conditions. There was a tendency that CO concentration increased as the firing rate increases. The reason for rise of CO concentration is that it becomes the relatively rich condition. The fiber burner exhibit significant both spectral intensity peaks in the bands at 2.5${\mu}m$ and 4.0${\mu}m$ relatively, There is a small difference in the variable mixing tube. However spectral intensity increased with the firing rate.

• 대한치과기공학회지
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• 제25권1호
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• pp.21-28
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• 2003

The purpose of this study was to process bio-active glass ceramic composite, reinforced with sapphire fibers, by hot press. Also to study the interface of the matrix and the sapphire fiber, and the mechanical properties. Glass raw materials melted in Pt crucible at 1300$^{\circ}C$ during 3.5 hours. The melt was crushed in ball mill and then crushed material, ground and sieved to $<40{\beta}{\mu}m$. Sapphire fibers cut (30mm) and aligned. Powder and fibers hot pressed. The micrographs show good bonding between the matrix and the fiber and no porosity in the glass matrix. This means ideal fracture phenomena. Glass is fractured before the fiber. This is indication of good fracture strength. EDXS showing aluminum rich phase and crystalline phase. Bright field image of the matrix showing crystalline phase. Also diffraction pattern of TEM showing the crystalline phase and more than one phase. Strength of the samples was determined by 3 point bend testing. Strength of the 10vol% sample was approximately 69MPa, while strength of the control sample is 35MPa. Conclusions through this study as follow: 1. Micrographs show no porosity in the glass matrix and the interface. 2. The interface between the fiber and the glass matrix show no gaps. 3. Fracture of the glass indicates characteristic fiber-matrix separation. 4. Presence of crystalline phase at high processing temperature. 5. Sapphire is compatible with bioactive glass.

• Journal of Ceramic Processing Research
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• 제20권1호
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• pp.48-53
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• 2019

Carbon fiber reinforced SiC composites (C/SiC) have high-temperature stability and excellent thermal shock resistance, and are currently being applied in extreme environments, for example, as aerospace propulsion parts or in high-performance brake systems. However, their low thermal conductivity, compared to metallic materials, are an obstacle to energy efficiency improvements via utilization of regenerative cooling systems. In order to solve this problem, the present study investigated the bonding strength between carbon fiber and matrix material within ceramic matrix composite (CMC) materials, demonstrating the relation between the microstructure and bonding, and showing that the mechanical properties and thermal conductivity may be improved by treatment of the carbon fibers. When fiber surface was treated with a nitric acid solution, the observed segment crack areas within the subsequently generated CMC increased from 6 to 10%; moreover, it was possible to enhance the thermal conductivity from 10.5 to 14 W/m·K, via the same approach. However, fiber surface treatment tends to cause mechanical damage of the final composite material by fiber etching.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1064-1069
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• 2004

Ceramic ferrules which are major parts of the fiber optic connectors are requiring high precisions in grinding. After grinding, it is the problem that subsurface damages cannot be removed. The objective of this study was to analyze the grinding force and the associated stress generated in a ceramic ferrule during cylindrically external griding using finite element analysis(FEA). A two-dimensional finite element model was constructed with the grinding parameters and the mechanical properties of the ferrule as input variables. The size of the geometric model was the same with ceramic ferrule. The experimental results are investigated by SEM photograph and compared with the results from FEM. The result of FEA showed a good agreement with that of experiment.