• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.648-651
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• 2011

본 논문에서는 3차원 섬유분포를 가정하여 고유동 섬유보강 시멘트 모르타르의 유동에 따른 섬유방향성변화를 해석적으로 파악해 보았다. 유동흐름은 평면상의 2차원 완전발달 전단흐름을 고려하였다. 유동에 따른 섬유의 회전운동은 섬유간의 상호 간섭효과를 무시한 Jeffery의 기본식에 근거하였다. 굳지 않은 섬유혼입 모르타르의 유동에 따른 섬유방향성 분포 변화를 흐름선과 동일 유동거리 상의 단면에 대해 파악하였다. 그 결과, 단면 내 위치에 따라서 섬유방향성 분포 변화가 크게 차이가 발생하는 것을 확인할 수 있었다. 또한 유동거리에 따른 단면상의 섬유방향성 분포는 초기 유동거리에서 분포 형상에 큰 변화가 발생하였고, 유동에 따라 섬유가 유동방향과 나란하게 놓이는 경향이 커지는 것을 확인할 수 있었다. 이러한 섬유방향성 변화의 예측은 섬유보강 시멘트 복합체의 인장특성에 예측하는데 유용하게 사용될 것이다.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.731-739
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• 2008

To evaluate the fiber orientation characteristics and estimate its effect on the flexural strength of steel fiber reinforced ultra high strength concrete with directions of concrete placing, we developed an image processing technique and carried out the flexural test to quantify the effect of fiber orientation characteristics on the flexural strength as well. The image processing technique developed in this study could evaluate quantitatively the fiber orientation property by the use of dispersion coefficient, the number of fibers in a unit area, and fiber orientation. It was also found that the fiber orientation characteristics were dependent on the direction of concrete placing. Fiber orientation characteristic was revealed to strongly affect the ultimate flexural strength, while hardly affecting the first cracking strength. Theoretical model for flexural strength was applied to compare with test results, which exhibited a good agreement.

• Composites Research
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• v.33 no.1
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• pp.30-37
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• 2020

Stress distributions dependent on fiber arrangements are studied using the two-dimensional representative volume element (RVE) model for uni-directionally continuous fiber-reinforced composites subjected to transverse tensile loading. It is easily expected that the stresses around the fibers are concentrated mainly due to the stiffness mismatch between the fiber and matrix materials. In this presentation, it is shown that the stresses are not always increased although the distance between two fibers is shortened. The 2D RVE models, originally having a regular hexagonal fiber array, is utilized to study the effect of the fiber locations on the stress distributions. As the central fiber is relocated, the stress distributions around the fiber are obtained through finite element analysis. It is found that the stresses around the fiber are strongly dependent on the fiber distance as well as the angle between the loading direction and the line connecting two fibers.

• Journal of the Korean Wood Science and Technology
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• v.36 no.4
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• pp.93-101
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• 2008

Bearing strength test was investigated to determine the bearing properties of domestic larix glulam according to the load direction (in parallel to grain and in perpendicular to grain), the fastener (bolt and drift-pin), and the direction of laminae. The specimen was 5 ply glulam. The diameters of fastener are 12, 16 and 20 mm. The results were as follows. 1) In according to the diameter of bolt and drift-pin, the average of maximum bearing strength in parallel to grain loading was similar to that in perpendicular to grain loading. The average of maximum bearing strength was 1.50~2.31 times higher in parallel to grain loading than in perpendicular to grain loading. The average of maximum bearing strength in parallel to grain loading was lowered by 20% with increasing the diameter from 16 mm to 20 mm, but that in perpendicular to grain loading didn't show a clear tendency. 2) The average of bearing stiffness in parallel to grain loading was the highest at 16 mm in diameter. The average of bearing stiffness is similar to the shearing stiffness in drift-pin connection with increasing diameter. 3) In parallel to grain loading, the failure mode of specimens was the splitting along the grain in decreasing diameter. The failure mode in perpendicular to grain loading was the splitting along the grain. In this case, split occured more in specimens using bolt than in those using drift-pin. 4) The 5% offset yield strength in parallel to grain loading was similar to the predicted bearing strength of KBCS, NDS. In perpendicular to grain loading, the NDS's equation can be applied to predict the bearing strength.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.639-646
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• 2009

High-flow steel-fiber reinforced mortar may induce a certain fiber orientation distribution in the process of placing and thus have an influence on the tensile properties. In this paper, the variation of the fiber orientation distribution according to the flow of high-flow steel-fiber reinforced mortar was estimated in numerical simulation. The analytical results present that the major variation of fiber orientation distribution is made within 150mm of flow distance, thereafter the tendency of the fiber orientation distribution is not noticeable even though the peak of distribution density in the orientation parallel to the flow direction get bigger along the distance. Considering the close relation between the fiber orientation and the tensile behavior of composite, prediction of fiber orientation distribution make it possible to predict the variation in the tensile behavior of high-flow steel-fiber reinforced mortar according to the flow.

• Journal of the Korea Institute of Building Construction
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• v.11 no.4
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• pp.326-332
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• 2011

Carbon, Aramid, Boron and Glass fibers are used as fibrous materials to promote structural bearing strength. Of these fiber types, carbon fiber is the most commonly used material, and is characterized by having a one-way direction, which is strengthened by tensile strength due to the attached direction only, while other types of fibers are two-way. Therefore, when applied in the field, the attachment direction of fiber is a very important factor. However, when fiber direction is not mentioned in the design drawing, there sometimes is no improvement in structural strength, as the fiber is being installed by a site engineer or workers who lack structural knowledge. The purpose of this study was to propose an optimal direction of carbon fiber through a comparison & analysis of reinforcing efficiency with reinforced experimental columns that used carbon fibers in each of the inclined, horizontal and vertical directions. According to the results, horizontal direction in the reinforced column was improved by 153.43%, but vertical direction was 104.61% only, and it was understood this was due to increased tensile strength along the fiber direction. For this reason, it is necessary to include information regarding fiber direction in design and site management.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.515-521
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• 1997

The effects of heat treatment and fiber orientation on tensile strength and fatigue behavior were studied in a continuously reinforced. magnesium-based composite Following an earlier TEM investigation, specimens were thermally aged to modified the interfacial zone between the alumina fibers and the magnesium alloy matrix. From the tensile experimental results, the ultimate tensile strength of the aged specimens were lower than that of the as-fabricated due to weak fiber-matrix interfacial strength with chemical reaction during the thermal processing. The fatigue crack growth experiments were conducted with specimens having the fiber orientation normal to the crack growth direction (longitudinal) and also specimens with the fibers oriented parallel to the crack growth direction(transverse). A comparison of the fatigue crack growth behavior indicates that aged longitudinal specimens are more resistant to fatigue crack growth the as-fabricated longitudinal specimens. Conversely, as-fabricated transverse specimens are more resistant to fatigue crack growth than aged transverse specimens.

• The Korean Journal of Rheology
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• v.4 no.2
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• pp.138-147
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• 1992

사출성형충전공정에서 금형구조가 단섬유배향에 미치는 영향을 예측하기 위하여 수 치모사 프로그램을 개발하였다. 유한요소 /관찰 부피 방법에 복잡한 금형에서의 유동을 해 석하고 섬유와 섬유간의 상호작용을 고려한 섬유배향텐서 변화식을 이용하여 입자 추적법으 로 섬유배향분포를 구하였다. 수치모사 결과 금형 옆벽면과 내부 방해체의 주위에 있는 섬 유들이 전단변형의 영향으로 그들주위를 따라서 정렬되려는 경향을 보였다, 두 유동이 내부 방해체를 지나 접하면서 생성된 웰드라인을 따라서 단섬유들이 정렬되려는 경향을 나타내엇 다. 그리고 수축유동에서는 흐름방향으로 정렬되나 확장유동에서는 흐름방향에 수직으로 배 열되려는 경향을 확인하였다. 위아래 벽에 의한 전단변형의 영향으로 서로 다른두 배향구조 를 보여주는 skin-core 구조를 두께방향의 속도구배를 고려한 수치모사를 통하여 예측할 수 있었다. skin구조에서는 섬유들이 흐름방향으로 정렬되고 core 구조에서는 흐름방향에 수직 으로 배향되는 것을 확인하였으며 섬유상호계수값이 커질수록 임의 배향화하는 경향을 보였다.

• The Korean Journal of Rheology
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• v.5 no.1
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• pp.49-64
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• 1993

사출성형충전공정에서 금형구조가 단섬유배향에 미치는 영향을 예측하기 위하여 수 치모사 프로그램을 개발하였다. 유한요소 /관찰 부피 방법에 복잡한 금형에서의 유동을 해 석하고 섬유와 섬유간의 상호작용을 고려한 섬유배향텐서 변화식을 이용하여 입자 추적법으 로 섬유배향분포를 구하였다. 수치모사 결과 금형 옆벽면과 내부 방해체의 주위에 있는 섬 유들이 전단변형의 영향으로 그들주위를 따라서 정렬되려는 경향을 보였다, 두 유동이 내부 방해체를 지나 접하면서 생성된 웰드라인을 따라서 단섬유들이 정렬되려는 경향을 나타내엇 다. 그리고 수축유동에서는 흐름방향으로 정렬되나 확장유동에서는 흐름방향에 수직으로 배 열되려는 경향을 확인하였다. 위아래 벽에 의한 전단변형의 영향으로 서로 다른두 배향구조 를 보여주는 skin-core 구조를 두께방향의 속도구배를 고려한 수치모사를 통하여 예측할 수 있었다. skin구조에서는 섬유들이 흐름방향으로 정렬되고 core 구조에서는 흐름방향에 수직 으로 배향되는 것을 확인하였으며 섬유상호계수값이 커질수록 임의 배향화하는 경향을 보였다.

• Restorative Dentistry and Endodontics
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• v.34 no.4
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• pp.364-370
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• 2009

The aim of this study was to evaluate the effect of fiber direction on the polymerization shrinkage of fiber-reinforced composite. The disc-shaped flowable composite specimens (d = 10 mm, h = 2 mm, Aeliteflo A2, Bisco, Inc., IL, USA) with or without glass fiber bundle (X-80821P Glass Fiber, Bisco, Inc., IL, USA) inside were prepared, and the longitudinal and transversal polymerization shrinkage of the specimens on radial plane were measured with strain gages (Linear S-series 350${\Omega}$, CAS, Seoul, Korea). In order to measure the free polymerization shrinkage of the flowable composite itself, the disc-shaped specimens (d = 7 mm, h = 1 mm) without fiber were prepared, and the axial shrinkage was measured with an LVDT (linear variable differential transformer) displacement sensor. The cross-section of the polymerized specimens was observed with a scanning electron microscope to examine the arrangement of the fiber bundle in composite. The mean polymerization shrinkage value of each specimen group was analyzed with ANOVA and Scheffe post-hoc test (${\alpha}$=0.05). The radial polymerization shrinkage of fiber-reinforced composite was decreased in the longitudinal direction of fiber, but increased in the transversal direction of fiber (p<0.05). We can conclude that the polymerization shrinkage of fiber-reinforced composite splint or restoratives is dependent on the direction of fiber.