• Journal of the Korean Ceramic Society
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• v.49 no.4
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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.

• Composites Research
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• v.35 no.2
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• pp.106-114
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• 2022

Carbon fiber-reinforced plastic, well known high specific strength and high specific stiffness, have been widely used in the aircraft industry. Mostly the CFRP structure is fabricated by lamination of carbon fiber or carbon prepreg, which has major disadvantage called delamination. Delamination is usually produced due to absence of the through-thickness direction fiber. In this study, three-dimensional carbon preform woven in three directions is used for fabrication of aircraft wing unit structure, a part of repeated structure in aircraft wing. The unit structure include skin, stringer and rib were prepared by resin transfer molding method. After, the 3D structure was compared with laminate structure through compression test. The results show that 3D structure is not only effective to prevent delamination but improved the mechanical strength. Therefore, the 3d preform structure is expected to be used in various fields requiring delamination prevention, especially in the aircraft industry.

• Carbon letters
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• v.25
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• pp.25-32
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• 2018

In this study, a thermal-gradient chemical vapor infiltration (TG-CVI) process was numerically studied in order to enhance the deposition uniformity within the preform. The computational fluid dynamics technique was used to solve the governing equations for heat transfer and gas flow during the TG-CVI process for two- and three-dimensional (2-D and 3-D) models. The temperature profiles in the 2-D and 3-D models showed good agreement with each other and with the experimental results. The densification process was investigated in a 2-D axisymmetric model. Computation results showed the distribution of the SiC deposition rate within the preform. The results also showed that using two-zone heater gave better deposition uniformity.

• Journal of the Korean Ceramic Society
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• v.28 no.8
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• pp.577-584
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• 1991

Among various forming techniques for ceramics, we have studied the slip casting method for the binary system of SiC and carbon. The stability of the slip of silicon carbide and carbon were investigated by measurements of zeta potential, viscosity, sedimentation height, and also studied as functions of PH and amounts of dispersants. A preform of SiC and C was prepared by slip casting and heat treatment at 400∼600$^{\circ}C$ under N2 gas. The preform was reacted with Si metal at 1550$^{\circ}C$, 10-1 mmHg to give rise a reaction bonded SiC with a density of 3.0g/㎤ and a bending strength of 580 MPa.

• Composites Research
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• v.33 no.2
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• pp.61-67
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• 2020

Preforming is crucial in resin transfer molding process using woven fabric. When shear deformation exceeds the locking angle, wrinkles are generated in the preform, which causes defects in the RTM process. Therefore, in this study, the allowable shear deformation limit of carbon fiber woven fabrics is quantified and the molding characteristics are verified using the actual fabric forming. As a result, the characteristics of creases according to the layer setups have been examined and the results have been discussed. Numerical analyses have been also performed using measured shear properties. These results have been compared with the experimental results.

• Journal of the Korean Ceramic Society
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• v.44 no.7
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• pp.381-386
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• 2007

A porous reaction bonded silicon carbide (RBSC) was fabricated by a molten Si infiltration method. The porosity and flexural strength of porous RBSC fabricated in this study were dependent upon the amount of carbon source used in the SiC/carbon preform as well as the amount of Si infiltrated into the SiC/carbon preform. The porosity and flexural strength of porous RBSC were in the range of $20 vo1.{\sim}49 vo1.%$ and $38{\sim}61 MPa$, respectively. With increase of carbon contents and molten Si for infiltration, volume fraction of the pores was gradually decreased, and flexural strength was increased. The porous RBSCs fabricated with the same amount of molten Si show less residual Si around neck with increase of carbon source, as well as a new SiC was formed around neck which resulted in the decreased porosity and improvement of the flexural strength. In addition, decrease of the porosity and increase of the flexural strength were also obtained by increase of the amount of molten Si with the same amount of carbon source. However, it was found that the flexural strength of porous RBSC depends on the porosity rather than the amount of the newly formed SiC in neck phase between SiC particles used as a starting material.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.63-66
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• 2003

The effect of punching density and material composition on the tensile properties and optimum condition of manufacturing of carbon needle punched perform was studies. The interlaminar tensile strength were increased but the intralaminar tensile strength were decreased with increasing punching density. In the case of the performs composed of continuous oxi-PAN fabrics, there was a considerable improvement of the interlaminar and intralaminar tensile strength.

• Carbon letters
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• v.4 no.1
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• pp.24-30
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• 2003

In this study, densified 4D carbon/carbon composites were made from carbon fiber and coal tar pitch through the process of pressure impregnation and carbonization and then followed by carbonization and graphitization. To improve the oxidative resistance of the prepared carbon/carbon composites, the surface of carbon/carbon composites was coated on SiC by the pack cementation method. The SiC coated layer was created by depending on the constitution of pack powder, and reaction time of pack-cementation. The morpology of crystalline and texture of these SiC coated carbon/carbon composites were investigated by XRD, SEM/EDS observation. So the coating mechanism of pack-cementation process was proposed. The oxidative res istance were observed through the air oxidation test, and then the optimal condition of pack cementation was found by them. Besides, the oxidative mechanism of SiC formed was proposed through the observation of SiC coated surface, which was undergone by oxidation test.

• Carbon letters
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• v.11 no.4
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• pp.304-310
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• 2010

To manufacture a carbon/carbon composite the coal tar pitch was used as the matrix precursor and the PAN (polyacrylonitrile)-based carbon fiber was used as the reinforcing material to weave 3-directional preform. For pressure carbonization HIP equipment was used to produce a maximum temperature of $1000^{\circ}C$ and a maximum pressure of 100 MPa. The carbonization was induced by altering the dwell temperature between $250^{\circ}C$ and $420^{\circ}C$, which is an ideal temperature for the moderate growth of the mesophase nucleus that forms within the molten pitch during the pressure carbonization process. The application of high pressure during the carbonization process inhibits the mesophase growth and leads to the formation of spherical carbon particles that are approximately 30 nm in size. Most particles were spherical, but some particles were irregularly shaped. The spread of the carbon particles was larger on the surface of the carbon fiber than in the interior of the matrix pocket.

• Carbon letters
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• v.1 no.3_4
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• pp.158-164
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• 2001

It is well known that the fabrication process of carbon/carbon composites is very complex. Above all, the carbonization process have major effect on the morphology development of carbon matrix. Carbon/carbon composites of 4-directional fiber preform were fabricated using the coal tar based pitch as a matrix precursor in this study. According to carbonization pressure of 1 bar, 100 bar, 600 bar, and 900 bar, morphological changes of cokes and matrix of composites were discussed. As the carbonization pressure increased to 600 bar, the flow pattern morphology of bulk mesophse was well developed. On the contrary, mosaic pattern morphology was found in case of 900 bar of carbonization pressure. It is confirmed that the carbonization pressure have profound effect on the degree of graphitization and crystal size of carbon matrix. Even in the highly densified carbon/carbon composites, large voids were still found in the matrix pocket region.