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Title |
Tensile Properties of Hybrid Fiber Reinforced Cement Composite according to the Hooked & Smooth Steel Fiber Blending Ratio and Strain Rate
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Authors |
손민재(Min-Jae Son) ; 김규용(Gyu-Yong Kim) ; 이상규(Sang-Kyu Lee) ; 김홍섭(Hong-Seop Kim) ; 남정수(Jeong-Soo Nam) |
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DOI |
https://doi.org/10.11112/jksmi.2021.25.3.31 |
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Keywords |
섬유 혼합 비율; 변형속도; 인장특성; 섬유 혼합 효과; 동적증가계수 Fiber blending ratio; Strain rate; Tensile properties; Fiber blending effect; Dynamic increase factor |
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Abstract |
In this study, the fiber blending ratio and strain rate effect on the tensile properties synergy effect of hybrid fiber reinforced cement composite was evaluated. Hooked steel fiber(HSF) and smooth steel fiber(SSF) were used for reinforcing fiber. The fiber blending ratio of HSF+SSF were 1.5+0.5, 1.0+1.0 and 0.5+1.5vol.%. As a results, in the cement composite(HSF2.0) reinforced with HSF, as the strain rate increases, the tensile stress sharply decreased after the peak stress because of the decrease in the number of straightened pull-out fibers by increase of micro cracks in the matrix around HSF. When 0.5 vol.% of SSF was mixed, the micro cracks was effectively controlled at the static rate, but it was not effective in controlling micro cracks and improving the pull-out resistance of HSF at the high rate. On the other hand, the specimen(HSF1.0SSF1.0) in which 1.0vol.% HSF and 1.0vol.% SSF were mixed, each fibers controls against micro and macro cracks, and SSF improves the pull-out resistance of HSF effectively. Thus, the fiber blending effect of the strain capacity and energy absorption capacity was significantly increased at the high rate, and it showed the highest dynamic increase factor of the tensile strength, strain capacity and peak toughness. On the other hand, the incorporation of 1.5 vol.% SSF increases the number of fibers in the matrix and improves the pull-out resistance of HSF, resulting in the highest fiber blending effect of tensile strength and softening toughness. But as a low volume fraction of HSF which controlling macro crack, it was not effective for synergy of strain capacity and peak toughness.
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