Composites Research

The Korean Society for Composite Materials (한국복합재료학회)
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Mechanical Properties of Carbon Fiber/Si/SiC and Carbon Fiber/C/SiC Composites

탄소섬유/Si/SiC 및 탄소섬유/탄소/SiC 복합재의 기계적 물성

  • 신동우 (경상대학교 재료공학부 무기복합재료 연구실) ;
  • 박삼식 (경상대학교 재료공학부 무기복합재료 연구실) ;
  • 김경도 (경상대학교 재료공학부 무기복합재료 연구실) ;
  • 오세민 (포항산업과학연구원 탄소재료 연구팀)
  • Published : 1999.06.01
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Abstract

Carbon woven fabric/C/SiC composites were fabricated by multiple impregnations of carbon woven fabric/carbon preform with the polymer precursor of SiC, i.e., polycarbosilane. In addition, two kinds of low density carbon/carbon preforms which had different fiber volume fraction and fiber orientation, i.e., a carbon woven fabric(${\thickapprox}$55 vol%)/carbon and a chopped carbon fiber${\thickapprox}$40 vol%)/carbon composites, were reaction-bonded with a silicon melt at 1$700^{\circ}C$ in a vacuum to fabricate dense carbon fiber/Si/SiC composites. The reaction-bonding process increased the density to ~2.1 g/$cm^3$ from 1.6 g/$cm^3$ and 1.15 g/$cm^3$ of a carbon woven and a chopped carbon preforms, respectively. All of the composites fractured with extensive fiber pull-out. The higher the density the higher the stiffness and proportional limit stress. The mechanical properties obtained from a three-point bend and tension tests were compared. The ratios of the peak tensile stresses to the bending strengths of a carbon woven and a chopped carbon composites were about one-third, respectively. The carbon woven fabric/Si/SiC composites with density of 2.06 g/$cm^3$ showed ~120 MPa of ultimate strength and ~80 MPa of proportional limit in bend testing.

탄소직포/탄소/SiC 복합재는 탄소직포/탄소 프로폼을 SiC의 유기전구체인 polycarbosilane에 다중함침 열처리하여 제조하였다. 더불어 탄소 섬유의 분율과 배열 형태가 다른 두 가지 종류의 저밀도 탄소/탄소 복합재 즉, 탄소직포($\thickapprox$55 vol%)/탄소 복합재와 chopped 탄소섬유($\thickapprox$40 vol%)/탄소 복합재를 $1700^{\circ}C$ 진공 분위기에서 용융 실리콘과 반응결합하여 고밀도의 탄소섬유/Si/SiC 복합재도 제조하였다. 이 반응 결합 공정 이전 각 밀도가 1.6g/$cm^3$인 탄소직포/탄소 복합재와 1.15g/$cm^3$인 chopped 탄소섬유/탄소 복합재는 반응결합 후 그 밀도가 각각 2.1g/$cm^3$로 증가하였다. 제조한 복합재는 전형적인 섬유강화 복합재의 파괴거동을 보였으며 반응결합 후 밀도와 stiffness 그리고 탄성 한계 강도 등은 모두 현저히 증가하였다. 3점 곡강도와 인장 시험으로 기계적 물성을 비교평가하였다. 탄소직포/탄소 복합재와 chopped 탄소섬유/탄소 복합재의 곡강도에 대한 인장 강도의 비는 약 1/3이었다. 탄소직포/Si/SiC 복합재의 밀도는 2.06g/$cm^3$, 최대 곡강도는 ~120 MPa, 탄성한계 응력은 ~80 MPa를 나타내었다.

Keywords

References

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