• Computers and Concrete
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• 제22권5호
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• pp.481-492
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• 2018

In this paper, a new hybrid fiber system (NHFS) is investigated for the application of slab. The steel fiber, polyvinyl alcohol (PVA) fiber and calcium carbonate ($CaCO_3$) whisker is added to form NHFS. The four-point bending test is carried out on the flexural properties of slab with plain, steel fiber, traditional hybrid fiber system (THFS) and NHFS reinforced cementitious composites. The flexural behavior is evaluated by ASTM C1018-97, JCI-SF4 and post-crack strength (PCS) technique. The evaluation parameters of flexural toughness such as toughness index (TI), equivalent flexural strength (EFS) and PCS are determined. The size of slab specimens is $15mm(thickness){\times}50mm(width){\times}200mm(length)$. The results show that adding $CaCO_3$ whisker to THFS can significantly improve the flexural strength, TI, EFS, PCS of the slab. The empirical relation between reinforcing index ($RI_v$) and flexural parameters show that flexural parameters of slabs increase first and then decrease; which indicates that optimum $RI_v$ values can be helpful in the considering the mix design of steel-PVA fibers-$CaCO_3$ whisker composites for achieving the desired flexural-related properties. The scanning electron microscopy is performed to observe the micro-morphological characteristics of the fracture surface, which proved the positive hybrid effect among the different fibers in cementitious composites. The NHFS can arrest the generation and propagation of the crack from micro to macro level.

• 대한기계학회논문집A
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• 제29권6호
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• pp.876-888
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• 2005

Tensile properties and fracture toughness of monolithic aluminum, fiber reinforced plastics and glass fiber/aluminum hybrid laminates under tensile loads have been investigated using plain coupon and single-edge-notched specimens. Elastic modulus and ultimate tensile strength of GFMLs showed different characteristic behaviors according to the Al kind, fiber orientation and composition ratio. Fracture, toughness of A-GFML-UD which was determined by the evaluation of $K_{IC}$ and $G_{IC}$ based on critical load was similar to that of GFRP-UD and was much higher than monolithic Al. Therefore, A-GFML-UD presented superior fracture toughness as well as prominent damage tolerance in comparison to its constituent Al. By separating Al sheet from GFMLs after the test, optical microscope observation of fracture zone of GFRP layer in the vicinity of crack tip revealed that crack advance of GFMLs depended on the orientation of fiber layer as well as Al/fiber composition ratio.

• Carbon letters
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• 제5권1호
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• pp.1-5
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• 2004

The effects of fiber surface-treatment and sizing on the dynamic mechanical properties of unidirectional and 2-directional carbon fiber/nylon 6 composites by means of dynamic mechanical analysis have been investigated in the present study. The interlaminar shear strengths of 2-directional carbon/nylon 6 composites sized with various thermosetting and thermoplastic resins are also measured using a short-beam shear test method. The result suggests that different surface-treatment levels onto carbon fibers may influence the storage modulus and tan ${\delta}$ behavior of carbon/nylon 6 composites, reflecting somewhat change of the stiffness and the interfacial adhesion of the composites. Dynamic mechanical analysis and short-beam shear test results indicate that appropriate use of a sizing material upon carbon fiber composite processing may contribute to enhancing the interfacial and/or interlaminar properties of woven carbon fabric/nylon 6 composites, depending on their resin characteristics and processing temperature.

• ETRI Journal
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• 제24권2호
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• pp.81-96
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• 2002

This paper describes our design of a hybrid amplifier composed of a distributed Raman amplifier and erbium-doped fiber amplifiers for C- and L-bands. We characterize the distributed Raman amplifier by numerical simulation based on the experimentally measured Raman gain coefficient of an ordinary single mode fiber transmission line. In single channel amplification, the crosstalk caused by double Rayleigh scattering was independent of signal input power and simply given as a function of the Raman gain. The double Rayleigh scattering induced power penalty was less than 0.1 dB after 1000 km if the on-off Raman gain was below 21 dB. For multiple channel amplification, using commercially available pump laser diodes and fiber components, we determined and optimized the conditions of three-wavelength Raman pumping for an amplification bandwidth of 32 nm for C-band and 34 nm for L-band. After analyzing the conventional erbium-doped fiber amplifier analysis in C-band, we estimated the performance of the hybrid amplifier for long haul optical transmission. Compared with erbium-doped fiber amplifiers, the optical signal-to-noise ratio was calculated to be higher by more than 3 dB in the optical link using the designed hybrid amplifier.

• Macromolecular Research
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• 제14권2호
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• pp.146-154
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• 2006

Organic and inorganic hybrid nanocomposites based on poly(ethylene 2,6-naphthalate) (PEN) and silica nanoparticles were prepared by a melt blending process. In particular, polymer nanocomposites consisting mostly of cheap conventional polyesters with very small quantities of inorganic nanoparticles are of great interest from an industrial perspective. The crystallization behavior of PEN/silica hybrid nanocomposites depended significantly on silica content and crystallization temperature. The activation energy of crystallization for PEN/silica hybrid nanocomposites was decreased by incorporating a small quantity of silica nanoparticles. Double melting behavior was observed in PEN/silica hybrid nanocomposites, and the equilibrium melting temperature decreased with increasing silica content. The fold surface free energy of PEN/silica hybrid nanocomposites decreased with increasing silica content. The work of chain folding (q) for PEN was estimated as $7.28{\times}10^{-20}J$ per molecular chain fold, while the q values for the PEN/silica 0.9 hybrid nanocomposite was $3.71{\times}10^{-20}J$, implying that the incorporation of silica nanoparticles lowers the work required to fold the polymer chains.

• Composites Research
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• 제27권1호
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• pp.14-18
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• 2014

탄소섬유 복합재료는 내열성 및 우수한 기계적 특성을 가지고 있는 우수한 재료이지만 가격이 비싼 결점이 있다. 따라서 본 연구에서는 높은 기계적 강도를 가지며, 가격이 비싸지 않은 재료의 개발을 위해 탄소섬유에 현무암 섬유를 첨가하여 하이브리드 복합재료를 제작하였다. 현무암 섬유의 함유 비율이 높아질수록 강도는 감소하였으며, 탄소의 강화재 비율이 80% 정도에서 CFRP와 유사한 강도를 얻을 수 있었다. 또한 섬유 각각을 적층하여 복합재료를 제작하는 것 보다 섬유사를 혼합시켜 제작한 복합재료에서 더 우수한 기계적 특성을 얻을 수 있었다.

• Advances in materials Research
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• 제4권2호
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• pp.97-111
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• 2015

Polypropylene short fiber (PP)-clay particulate-epoxy ternary composites were prepared by reinforcing PP short fiber and clay particles in the range of 0.1 phr to 0.7 phr into epoxy resin. Prepared hybrid composites were characterized for their mechanical, thermal and flame retardant properties. The obtained results indicated an increase in impact resistance, tensile strength, flexural strength and Young's modulus to an extent (up to 0.5 phr clay and 0.5 phr PP short fiber) and then decreases as the reinforcing phases are further increased. The thermal stability of these materials are found to increase up to 0.2 phr clay and 0.2 phr PP addition, beyond which it is decreased. Addition of clay is found to have the negative effect on epoxy-PP short fiber composites, which is evident from the comparison of mechanical and thermal properties of epoxy-0.5 phr PP short fiber composite and epoxy-0.5 phr PP short fiber-0.5 phr clay composite hybrid. UL-94 tests conducted on the composite hybrids have showed a reduction in the burning rate. Morphological observations indicated a greater fiber pull with the addition of clay. The performed tests in the present study indicated that materials under investigation have promising applications in construction, agriculture and decorative purposes.

• Journal of the Korean Wood Science and Technology
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• 제40권6호
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• pp.406-417
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• 2012

이 연구에서는 선행연구에서 발표된 목재섬유에 녹차를 복합한 친환경 복합보드에 탈취성과 흡착성 등의 기능성을 보강한 건축내장재를 개발하기 위하여, 흑탄, 백탄, 활성탄 등 3종류의 숯을 혼합한 녹차-숯-목재섬유 복합보드를 제작하였고, 구성원료의 종류 및 배합비율이 복합보드의 치수안정성, 탈취성 및 포름알데히드 방산량에 미치는 영향을 조사하였다. 녹차-숯-목재섬유 복합보드의 흡수두께 팽창률은 녹차와 숯의 배합비율의 증가에 따라 증가하였으나, 활성탄 함유 복합보드를 제외하고, KS에 규정된 그 값보다 현저히 낮은 값을 나타내었다. 복합보드의 암모니아가스 감소율은 활성탄 10% 함유 복합보드에서 30분 경과시 96%의 높은 값을 나타내었고, 다른 모든 복합보드에서도 1시간 경과 후 거의 95%전후의 높은 암모니아가스 감소율을 나타내었다. 복합보드의 포름알데히드 방산량은 $E_1$급 요소수지를 사용했을 경우, $E_0$급에 가까운 방산량을, $E_0$급 요소수지를 사용했을 경우는 super $E_0$급의 낮은 포름알데히드 방산량을 나타내는 것이 확인되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.644-647
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• 2004

Modulus of rupture (MOR) and flexural toughness in hybrid fiber reinforced cement pastes mixed with micro-fiber (carbon fiber) and macro-fiber (steel fiber) and replaced with silica fume according to the fixed ratio were researched. Reinforcing efficiency in specimens were estimated by two factors, such as strengthening factor $(F_s)$ and toughening factor $(F_t)$, which were calculated from the analysis of variance (ANOVA) of the response values, such as MOR and absorbtion energy $(W_0)$. According to the experimental design by the fractional orthogonal array, nine hybrid fibrous reinforced paste series and one non-reinforced control paste were manufactured. Specimens of each series were tested by the INSTRON Inc. 8502(model) equipment in three-points bending and then measured the load-deflection response relationships. Considerable strengthening of cement pastes resulted in' the case of other factors without carbon fiber and toughening of cement pastes about all factors showed high. Based on the significance of factors related to response values from ANOVA, following assessments were available; $F_s$ or MOR: silica fume $\gg$ steel fiber $\gg$ carbon fiber; $F_t\;or\;W_0$: steel fiber > carbon fiber > silica fume. Optimized composition condition was estimated by steel fiber of $1.5\%$, carbon fiber of $0.5\%$ and silica fume $7.5\%$ in side of strengthening and steel fiber of $1.5\%$, carbon fiber of $0.75\%$ and silica fume $7.5\%$ in side of toughening.

• 한국구조물진단유지관리공학회 논문집
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• 제23권2호
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• pp.60-66
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• 2019

콘크리트의 낮은 인장강도 및 균열제어 능력 등의 약한 재료성질을 개선하기 위하여 수년간 하이브리드 섬유보강 콘크리트에 관한 많은 연구가 진행되어 왔다. 그러나 비정질 강섬유와 유기섬유를 이용한 하이브리드 섬유보강 콘크리트에 관한 연구는 이루어지지 않은 실정이다. 따라서, 본 연구의 목적은 비정질 강섬유와 유기섬유로서 폴리아미드 섬유를 이용한 하이브리드 섬유보강 콘크리트의 압축강도, 장기 건조수축 및 내동해성을 평가하는 것이다. 이를 위하여 목표 압축강도 40 및 60 MPa 각각에 대해서 하이브리드 섬유 혼입률을 전체 체적비로 1.0%로 설정하여 비정질 강섬유와 폴리아미드 섬유를 이용한 하이브리드 섬유보강 콘크리트를 제작하였다. 제작된 하이브리드 섬유보강 콘크리트의 장기 건조수축 및 내동해성을 평가한 결과, 재령 365일 및 730일에서의 장기 길이변화율은 플레인 콘크리트보다 각각30%, 25% 이상 감소된 것으로 나타났으며, 동결융해 300 사이클 후의 내구성 지수는 90% 이상으로, 내동해성이 있는 것으로 나타났다.