• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.199-202
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• 2002

Interfacial properties and electrical sensing for fiber fracture in carbon and SiC fibers/epoxy composites were investigated by the electrical resistance measurement and fragmentation test. As fiber-embedded angle increased, interfacial shear strength (IFSS) of two-type fiber composites decreased, and the elapsed time was long to the infinity in electrical resistivity. The initial slope of electrical resistivity increased rapidly to the infinity at higher angle, whereas electrical resistivity increased gradually at small angle. Furthermore, both fiber composites with small embedded angle showed a fully-developed stress whitening pattern, whereas both composites with higher embedded angle exhibited a less developed stress whitening pattern. As embedded angle decreased, the gap between the fragments increased and the debonded length was wider for both fiber composites. Electro-micromechanical technique can be a feasible nondestructive evaluation to measure interfacial sensing properties depending on the fiber-embedded angle in conductive fiber reinforced composites.

• Carbon letters
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• 제6권4호
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• pp.234-242
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• 2005

Bending and tensile properties of 2D cross-ply C/C composites with processing heat treatment temperature (HTT) are evaluated. C/C composites used are made from two types of PAN based T700 and M40 carbon fibers with phenolic resin as carbon matrix precursor. Both the types of composites are heat treated at different temperatures (ranging from 750 to $2800^{\circ}C$) and characterized for bending and tensile properties. It is observed that, real density and open porosity increases with HTT, however, bulk density does show remarkable change. The real density and open porosity are higher in case T-700 carbon fiber composites at $2800^{\circ}C$, even though the density of M40 carbon fiber is higher. Bending strength is considerably greater than tensile strength through out the processing HTT due to the different mode of fracture. The bending and tensile strength decreases in both composites on $1000^{\circ}C$ which attributed to decrease in bulk density, thereafter with increase in HTT, bending and tensile strength increases. The maximum strength is in T700 fiber based composites at HTT $1500^{\circ}C$ and in M40 fiber based composites at HTT $2500^{\circ}C$. After attending the maximum value of strength in both types of composite at deflection HTT, after that strength decreases continuously. Decrease in strength is due to the degradation of fiber properties and in-situ fiber damages in the composite. The maximum carbon fiber strength realization in C/C composites is possible at a temperature that is same of fiber HTT. It has been found first time that the bending strength more or less 1.55 times higher in T700 fiber composites and in M40 fiber composites bending strength is 1.2 times higher than that of tensile strength of C/C composites.

• 한국안전학회지
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• 제23권6호
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• pp.34-37
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• 2008

The composite materials are widely used in the many applications of industry as well as aerospace field because of their high specific stiffness and strength which benefits the material and provides potential energy savings. However, composite materials also have a low property about external applied impact. In this paper, impact tests were conducted on different sample types(glass, carbon and kevlar composite) to obtain information such as absorbed energy and composite deformation using an instrumented impact test machine (DYNATUP 8250). 3 type samples were compared to experimental results. The data from impact test provided valuable information between the different type samples by wet lay up. This paper shows results of that kevlar composite has larger absorption energy and deformation than others.

• Carbon letters
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• 제12권1호
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• pp.26-30
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• 2011

For polyacrylonitrile (PAN) based carbon fiber (CF) process, we developed a lab scale wet spinning line and a continuous tailor-made stabilization system with ten columns for controlling temperature profile. PAN precursor was spun with a different spinning rate. PAN spun fibers were stabilized with a total duration of 45 to 110 min at a given temperature profile. Furthermore, a stabilization temperature profile was varied with the last column temperature from 230 to $275^{\circ}C$. Stabilized fibers were carbonized in nitrogen atmosphere at $1200^{\circ}C$ in a furnace. Morphologies of spun and CFs were observed using optical and scanning electron microscopy, respectively. Tensile properties of resulting CFs were measured. The results revealed that process conditions such as spinning rate, stabilization time, and temperature profile affect microstructure and tensile properties of CFs significantly.

• 한국해양공학회지
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• 제7권1호
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• pp.25-32
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• 1993

In composite materials, the fracture perpendicular to the fiber direction usually shows a non-linear behavior accompannying blunting and plastic deformation around the crack tip. In this study, the fracture thoughness in random short fiber SMC composite material and Carbon/Epoxy composite material is estimated by the A.M.(Area Method) and the G.L.M.(Generalized Locus Method) which can determine a stable total energy release rate(G$_T$) not only in highly elghly elastic material but also in highly non-linear materials.

• 한국세라믹학회지
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• 제49권4호
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• pp.287-294
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• 2012

Ceramic Matrix Composites (CMCs) represent a class of non-brittle refractory materials for harsh and extreme environments in aerospace and other applications. The quasi-ductility of these structural materials depends on the quality of the interface between the matrix and the fiber surface. In this study, a manufacture route is described where in contrast to most other processes no additional fiber coating is used to adjust the fiber/matrix interfaces in order to obtain damage tolerance and fracture toughness. Adapted microstructures of uncoated carbon fiber preforms were developed to permit the rapid infiltration of molten alloys and the subsequent reaction with the carbon matrix. Furthermore, any direct reaction between the melt and fibers was minimized. Using pure silicon as the reactive melt, C/SiC composites were manufactured with an aim of employing the resulting composite for friction applications. This paper describes the formation of the microstructure inside the C/C preform and resulting C/C-SiC composite, in addition to the MAX phases.

• Advances in aircraft and spacecraft science
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• 제2권3호
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• pp.263-273
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• 2015

Carbon nanotube strain sensors, or so called "fuzzy fiber" sensors have not yet been studied sufficiently. These sensors are composed of a bundle of fiberglass fibers coated with CNT through a thermal chemical vapor deposition process. The characteristics of these fuzzy fiber sensors differ from a conventional nanocomposite in that the CNTs are anchored to a substrate fiber and the CNTs have a preferential orientation due to this bonding to the substrate fiber. A numerical model was constructed to predict the strain response of a composite with embedded fuzzy fiber sensors in order to compare result with the experimental results obtained in an earlier study. A comparison of the numerical and experimental responses was conducted based on this work. The longitudinal sensor output from the model matches nearly perfectly with the experimental results. The transverse and off-axis tests follow the correct trends; however the magnitude of the output does not match well with the experimental data. An explanation of the disparity is proposed based on microstructural interactions between individual nanotubes within the sensor.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.180-183
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• 2001

Glass fiber reinforced plastic(CFHP) tent pole fabricated by the pultrusion process with unidirectional glass fiber is two times as heavy as aluminum tent pole owing to the low specific modulus The first objective of this research is the design the high strength and light weight tent pole compete with. the second is the develope glass fiber carbon fiber hybrid tent pole pultrusion process. the third is the evaluate the mechanical properties of the hybrid tent pole compare to these of the duralumin tent pole.

• Composites Research
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• 제36권3호
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• pp.154-161
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• 2023

본 연구에서는 경량화를 위해 금속 링크를 탄소섬유/에폭시 복합재 링크로 대체하고자 파손 기준을 이용하여 복합재 링크가 주어진 하중 조건을 견딜 수 있는지를 평가하였다. 복합재의 파손 양상을 예측하기 위해 MMF 기준을 이용하였고, 기계적 시험을 수행하여 MMF의 기준 강도 파라미터를 구하였다. 연구결과 링크의 구멍 주위에서 응력집중이 발생하였고, 특히 굽힘 하중을 받을 때 링크 끝단과 구멍 주위에서 취약함이 드러났다. 파손 지수로부터 파손 양상을 예측하였고 매트릭스 인장 파손이 링크 끝단에서, 그리고 구멍 주위에서는 섬유의 압축 파손이 예측되었다. 본 연구를 통해 확보된 방법과 결과는 경량화를 위해 금속 부품을 탄소섬유/에폭시 복합재로 대체할 때 특정 하중 조건 하에서 복합재의 안전성을 평가하는 유용한 지침으로 활용할 수 있을 것이다.

• 한국세라믹학회지
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• 제35권9호
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• pp.974-980
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• 1998

This study is concerned with the production of carbon fiber reinforced carbon(C/C) with polyaromatic mesophase pitch as matrix precursor and with the investigation of friction-wear characteristics in ambient air using a constant speed type of friction tester. The main problem in using the polyaromatic mesophase as the matrix precursor is the high viscosity which may limit the complete impregnation of the fiber preform in the vacuum. To solve these problems two dimensional carbon fiber fabrics were infiltrated with meso-phase pitch in the pitch impregnator. After the impregnation and the heat treatment process. C/C com-posites were characterized by density porosity to monitor the influence of high pressure and temperature. It showed that the bulk density was increased and the apparent porosity and the density increasing rate was reduced as repeating the impregnation the carbonization and the heat treatment. The friction-wear charac-teristics of C/C composites were investigated by measuring the average friction coefficient and the specific wear rate as functions friction speed and friction pressure using a constant speed type of friction tester. C/C composite4s showed the average friction coefficient to be reduced as increasing the friction speed and the friction pressure.