• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.314-320
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• 2022

The function of reinforcing fibers used in building materials is to maintain resistance to bending loads and to function for cracking caused by drying shrinkage. High-density fiber-cement composites are mainly used for linear plates and are used to increase bending resistance. Therefore, tensile properties, bonding strength with cement hydrate, alkali resistance, and the like are required. Recently, as the non-combustible performance has been strengthened, a function to minimize the occurrence of sparks during high-temperature heating has been added. Therefore, the use of organic fibers is limited. In this study, a study was conducted to replace polypropylene used as reinforcing fiber with hemp fiber with excellent heat resistance. Hemp fibers have excellent heat resistance, good affinity with cement, and excellent alkali resistance. Based on the total volume of polypropylene fibers used in the existing formulation, the non-combustible performance was compared and evaluated by using hemp fibers instead of the polypropylene fibers, and basic physical properties such as flexural strength were tested. As a result of conducting a non-combustibility and physical property test using hemp fibers with a fiber length of 7 mm using 2 % and 3 % by weight, it was found that there is no remaining time of the flame, and the flexural strength can be secured at 95 % level of the existing polypropylene fiber.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.4
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• pp.18-24
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• 1994

This paper discusses experimental results obtained by the potentiality of cross-correlation function as a tool for analyzing propagation of wave in an aluminum and a woven glass fiber composite. Each propagated wave has its own characteristic time delay, and examination of the cross-correlation of input and output signal give the most proper wave velocity and significant path. Using the above distinctive features, we observed the propagation velocity for the aluminum alloy and a woven glass fiber composite more acurately and easily then the common methods. The fiber locations of this composite also determined by the basis of these results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.37-45
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• 2021

This paper is a basic study to evaluate the possibility of earthquake-resistant reinforcement by reinforcing engineered cementitious composite in masonry members. In order to examine the performance according to the fiber mixing rate of the engineered cementitious composite, a test specimen was prepared according to the formulation design, and flow ability, compressive strength, flexural strength, length change rate, and direct tensile strain were measured. In addition, non-reinforced masonry members, masonry members reinforced with engineered cementitious composite, and masonry members in which glass fibers and wire mesh were separately reinforced with engineered cementitious composites were manufactured, and flexural strength and maximum displacement were measured. All specimens reinforced with engineered cementitious composite showed more than 16 times the effect of maximal strength compared to that of no reinforcement, and as a result of examining the crack shape, the energy dissipation ability was excellent, confirming the possibility of seismic reinforcement.

• Magazine of the Korea Concrete Institute
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• v.13 no.5
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• pp.77-81
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• 2001

부식 열화는 교량 기술자들에게 있어서 지속적인 도전을 요구하는 문제가 되어왔는데, 스텔스 항공기를 개발하게 한 새로운 재료 기술은 교량의 부식을 해결할 수 있게 하였다. 즉, 경량의 고강도 재료로 높은 피로 저항성을 갖고 있고, 부식에 강한 복합체는 교량의 재료로서 아주 바람직한 성질을 갖고 있다 섬유 보강 폴리머(FRP) 복합재료를 교량의 건설에 이용하려는 프로젝트는 1998년 현재 80 여 개가 넘게 진행되고 있는데, 이 중 미국 내에서 31개의 프로젝트가 수행되고 있다. 이 글은 미국 내에서 FRP복합체를 교량 공학 분야에 적용하려는 초기의 성공적인 시도들에 관한 내용으로 복합체의 장점, 특성, 교량 적용시 고려 사항, 그리고 향후 복합재료에 관한 기술을 토목 구조물에 적용하는데 필요한 소요 기술 등에 관하여 정리한 것이다. 이 새로운 재료는 신설 구조물의 건설과 기존 교량의 보수 및 보강에 모두 적용할 수 있으며, FRP복합체 기술을 토목 구조물과 기반 시설물 건설 분야에 적용하는 것은 지금까지 성공적인 결과를 보여 주고 있다 미국연방도로국(FHWA, Federal Highway Administration)은 이 기술을 미국 내 교통 기반 시설물인 신규 교량의 건설은 물론 기즌 교량의 보수 및 보강에 활용하는 방안에 대하여 관심을 갖고 있다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.73-74
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• 2018

In this study, it evaluate the tensile properties of polyamide fiber reinforced cementitious composite and hooked steel fiber reinforced cementitious Composites by strain rate. Polyamide fiber reinforced cement composites (PAFRCC) and Hooked Steel Fiber Reinforced Cement Composite(HSFRCC) were fabricated. Each specimen was reinforced with 1.0 and 2.0vol% fiber. The length of the reinforced fiber was 30 mm for both fibers, and the tensile test specimen was made in dumbbell shape. As a result, the tensile strength of fiber in polyamide fiber and the mechanical bonding between fiber and matrix in hooked steel fiber are considered to be the main factors affecting tensile behavior of fiber reinforced cement composite.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.925-928
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• 2008

Fiber is an important ingredient in strain-hardening cementitious composite (SHCC), which can control fracture of cementitious composite by bridging action. The properties of reinforcing fiber, as tensile strength, aspect ratio and elastic modulus, have great effect on the fracture behavior of SHCC. To apply SHCC to structural member, SHCC must have economical efficiency and workability as well as own excellent tensile performance. For these purposes, four-point bending and direct tensile tests on SHCC with only hybrid synthetic fibers, total fiber volume fraction, $V_f$, is 1.5%, are carried out. The research emphasis is on the mechanical properties of SHCC made in Polyvinyl alcohol (PVA) and Polyethylene (PE) fibers, and how this affects the composite property, and ultimately its strain-hardening performance. Also, effect of hybrid type and water-cement ratio on the behavior of SHCC was evaluated in this paper.

• Journal of the Korean Arthroscopy Society
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• v.10 no.1
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• pp.83-86
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• 2006

Purpose: We repoted the clinical results and introduction of surgical techniques for the patients with tears of the triangular fibrocartilage complex (TFCC) who had arthroscopic management. Materials and Methods: According to Palmer classification, nine patients(9 wrists) with type 1B lesions of the triangular fibrocartilage complex from 2001 to 2004 were included in this study. The mean follow-up period was 28 months. Six were male and three were female, right side was in seven cases and left side in two cases. Nine patients received arthroscopic debridement and repair by outside-in technique. To assess the clinical outcomes, the visual analogue pain scale(VAPS), grip strength, range of motion were investigated. Results: The average of VAPS improved from 6.2 to 1.4. The grip strength of wrists of all nine patients improved after surgery and the range of motion of all wrists reached full range. Conclusion: Arthroscopic repair of type 1B tear of the triangular fibrocartilage complex has satisfactory results. The repair by outside-in technique was simple and we could have secure fixation.

• Journal of the Korean Arthroscopy Society
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• v.5 no.1
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• pp.32-35
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• 2001

Purpose : To evaluate the efficacy of arthroscopic management of the triangular fibrocartilage complex(TFCC). Materials and Methods : Thirteen patients(14 wrists) with acute or chronic traumatic triangular fibrocartilage complex lesions were included in the study. The mean patients' age was 28.3 years, with a range of 21 to 45 years. All patients were diagnosed by physical examination, arthrographic or magnetic resonance imaging studies. Eight of the 14 wrists had central TFCC tear while 6 wrists had peripheral tear. Under arthroscopic control, injuries to the central portions were treated by debridement and excision of unstable tissue fragment while peripheral tears were repaired. The follow-up period averaged 28 months. The results were analyzed clinically using the Mayo modification of the Green and O' Brien wrist scoring system. Results : Nine of the 14 wrists were rated excellent,3 good and 2 fair Overall, 12 of the 14 patients rated as satisfactory and returned to sports or work activities. Conclusion : Arthroscopic treatment of TFCC resulted in a high degree of patient satisfaction and an increase in the ability to perform at workshop.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3990-3996
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• 2014

Because the physical properties can be decreased when a Nylon 66/glass fiber composite is injected into a mold over $300^{\circ}C$, a systematic study of the thermal history in the case of re-use is needed. Nylon 66/glass fiber extrudates as a function of the extrusion number were prepared using a twin screw extruder at 305/290/273/268/265/$260^{\circ}C$. The chemical structure, thermal properties, melt index, crystal structure, Izod impact strength, and rheological properties were measured by Fourier transform infra-red (FT-IR), melt indexer, DSC, TGA, XRD, Izod impact tester, and dynamic rheometer. The FT-IR spectra indicated that the number of extrusions did not affect the chemical structure. The decrease in molecular weight with increasing extrusion number was confirmed by the melt index and the complex viscosity of extrudates. Based on the DSC and TGA results, the thermal history had no effect on the melting temperature, regardless of the number of extrusions, but the degradation temperature decreased up to $20^{\circ}C$ with increasing extrusion number. The Izod impact strengths of the extrudates were found to decrease with increasing extrusion number. No structural change after extrusion was also confirmed because there was no change in the slope and shape of the G'-G" plot.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.149-157
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• 2017

As the amount of construction wastes increase, reuse of recycled materials is being considered in research areas. While there are many experimental investigations focusing on development of mortar and concrete using the recycled materials, the studies regarding the fiber-reinforced cement composites (FRCCs) using recycled materials are still limited. In this paper, an experimental attempt has been made to investigate the effect of recycled fine aggregates and fly ash on the mechanical properties of PVA FRCCs. The cement and natural sand were respectively replaced by fly ash and recycled fine aggregates at two content levels, 25% and 50%. Ten types of PVA FRCCs mixes were fabricated and tested to investigate the flexural, compressive and direct tensile behaviors. The test results show that flexural, compressive and direct tensile strength were decreased with increase in fly ash content at all ages. In particular, flexural, compressive and direct tensile strengths of specimens, containing 50% recycled fine aggregates and 50% fly ash, showed the lowest values. The modulus of elasticity of specimens showed similar trend to the 28-day compressive strength. Poisson's ratio was increased with increase in fly ash and recycled fine aggregates content.