• 한국농공학회지
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• 제45권6호
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• pp.162-171
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• 2003

Traditional methods of earth reinforcement consist of introducing strips, fabrics, or grids into an earth mass. Recently, discrete fibers are simply added and mixed with the soil, much the same as cement, lime or other additives. The advantages of randomly distributed fibers is the maintenance of strength isotropy, low decrease in post-peak shear strength and high stability at failure. In this study, new composite reinforcement structures which consist of geotextile and randomly distributed discrete fibers were examined their engineering properties, such as shear strength of the composite reinforced soil and permeability of short fiber reinforced soil. The increments of shear strength of composite reinforced soils were the sum of increments by fiber and woven geotextile, respectively. The permeability of short fiber reinforced soil was increased with fiber mixing ratio.

• 대한기계학회논문집
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• 제18권4호
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• pp.887-902
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• 1994

Within the framework of anisotropic thermoelasticity, the problem of an interlaminar crack in a laminated fiber-reinforced composite subjected to a uniform heat flow is investigated. Under a state of generalized plane deformation, dissimilar anisotropic half-spaces with different fiber orientations are considered to be bound together by a matrix interlayer containing the crack. The interlayer models the matrix-rich interlaminar region of the fibrous composite laminate. Based on the flexibility/stiffness matrix approach, formulation of the current crack problem results in having to solve two sets of singular integral equations for temperature and thermal stress analyses. Numerical results are obtained, illustrating the parametric effects of laminate stacking sequence, relative crack size, crack location, crack surface partial insulation, and fiber volume fraction on the values of mixed mode thermal stress intensity factors.

• 한국공작기계학회논문집
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• 제10권1호
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• pp.88-93
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• 2001

Carbon fiber epoxy composite are widely used in airframe structures, space vehicles, sports equipment, and high speed reciprocating parts for industrial machinery. In this paper, the groove processing characteristics of carbon fiber epoxy com-posite was experimentally investigated in order to study the endmill operation of fiber reinforce epoxy composites. Followings are main finding from the experimental results. First, the cutting and bending force in groove processing of the carbon fiber epoxy composite increased as the spindle speed deceased. They also deceased as the table feed increased. Second, the good cutting status obtained at the entrance of groove while delamination occurred at the exit of groove, Third, the regular high speed steel endmill was not efficient, thus the new endmill such as coated carbide rooter endmill or dia-mode endmill should be used for the effective endmll operation of carbon filber epoxy composites.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.31-36
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• 2003

Recently, composite materials are widely used for nozzle, pressure vessel, skins of satellite and many structures under condition of high temperature due to good thermal characteristics such as low CTE, heat-resistance, etc. Fiber optic sensors, especially FBG(fiber Bragg grating) sensors, can be a good counterproposal of strain gages for the measurement of material properties of composites under high temperature. In this research, T700/Epoxy specimens with embedded FBG sensors were fabricated and tested at the Instron with thermal chamber from room temperature to $400^{\circ}C$. The effects of embedding optical fiber on material properties were also verified. And, the experimental results were discussed and analyzed by microphotographs of the composite specimen.

• 한국생산제조학회지
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• 제6권3호
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• pp.89-95
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• 1997

A simulation to investigate the thermal behavior in short fiber or whisker reinforced composite materials has been performed for the application to the thermoelastic stress analysis using Finite Element Method (FEM). To obtain the internal field quantities of composite material, the procedure of micromechanical modeling and the principle of virtual work were implemented. For the numerical illustration, an aligned axisymmetric single fiber model has been employed to assess field quantities. It was found that the proposed simulation methodology for thermoelastic stress analysis is applicable to the complicated inhomogeneous solid for the investigation of micromechanical thermoelastic behavior.

• 구강회복응용과학지
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• 제22권1호
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• pp.23-27
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• 2006

This case reports describe a new approach to the use of polymers in orthodontics, using a fiber reinforced composite(FRC). FRC was successfully used in a periodontal splints, fiber post for endodontic use, orthodontic retainer and space maintainers, implant prosthesis, large span bridge, management of cracked tooth, anchorage reinforcement in orthodontics. FRC has highly favorable mechanical properties, and its strength-to-weight ratios is superior to those of most alloys. FRC has potential for use in many applications in dentistry and is expected to gain increasing application and popularity in dentistry. These case reports show that FRC is a promising anchorage reinforcement material for use in orthodontic practice.

• Advanced Composite Materials
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• 제18권3호
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• pp.197-208
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• 2009

Changes occurring in jute and coir fiber composites with 2-8% concentration of a NaOH treatment for 24 h were investigated, respectively, for void content, microscopy images, mechanical properties and water absorption. The jute and coir fibers were vacuum dried before molding composite specimens. Mechanical properties indicated good adhesion between natural fibers and PP. Jute fibers, when alkali-treated with 2% concentration for 24 h, showed best improvement in tensile strength by 40% and modulus by 9%, respectively, while coir fibers, when alkali-treated with 6% concentration for 24 h, showed best improvement in tensile strengths by 62% and modulus by 17%, respectively. With 2% concentration of alkali-treatments, the elongation of jute and coir composites reached 8% and 13.5%, respectively. Moisture absorption for jute and coir composites are 50% and 60% lower than untreated fiber composites, respectively.

• Composites Research
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• 제36권2호
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• pp.80-85
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• 2023

원통형 복합재 격자 구조는 필라멘트 와인딩 공법으로 제작되며 제작 공정에서 두께방향 섬유체적비 불균일이 발생할 수 있다. 섬유체적비 불균일은 구조의 강성에 영향을 미칠 수 있으며 강성 및 좌굴 특성이 변화할 수 있다. 본 연구에서는 두께방향 섬유체적비 불균일이 복합재 격자 구조의 비틀림 좌굴 하중에 미치는 영향에 대하여 분석하였다. 섬유체적비 변화에 의한 강성 변화를 유한요소 모델에 적용하였고 비틀림 하중을 가한 뒤 좌굴 해석을 수행하였다. 두께방향 섬유체적비 편차에 따른 좌굴 하중을 비교하였다. 섬유체적비 불균일에 의해 비틀림 좌굴 하중이 저하될 수 있음을 확인하였다.

• 한국산학기술학회논문지
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• 제17권5호
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• pp.80-85
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• 2016

탄소섬유강화 복합재는 기계적 물성이 우수하여 다양한 산업분야에서 활용되고 있으나 섬유길이가 짧은 단섬유 형태로 함침 되고 있어 강도와 강성을 증대시키는데 한계가 있다. 이를 보완하기 위한 LFT-D성형은 탄소 또는 유리섬유를 열가소성 수지와 혼합하여 압출 후 프레스 성형하여 제품을 만드는 공법으로 연속공정이 가능하고 사출성형에 비해 생산성이 높아 자동차 구조용 부품을 제작하는데 사용할 수 있다. 본 연구에서는 LFT-D공법으로 성형된 탄소 장섬유강화 열가소성 복합소재의 기계적 특성을 파악하기 위하여 탄소 장섬유의 함침과 압출공정을 수행할 수 있는 Lab scale의 소형 압출기 시스템을 제작하였다. Lab scale의 소형 압출기를 사용하여 제작된 탄소 장섬유 복합소재를 프레스 성형하여 시편을 제작하고 재료의 기계적 특성을 평가한 결과, 탄소섬유길이, 프레스 가압압력 및 탄소섬유 함유량이 복합소재의 강도 및 강성의 증가에 영향을 미침을 알 수 있었다. 향후 탄소 장섬유 복합소재의 기계적 성질 향상을 위해서 혼합 스크류 설계, 탄소 섬유코팅 등에 대한 추가적인 연구가 필요하다.

• The Journal of Advanced Prosthodontics
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• 제6권3호
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• pp.200-206
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• 2014

PURPOSE. This in vitro study investigated the fracture resistance of endodontically treated premolars restored using silorane-or methacrylate-based composite along with or without fiber or nano-ionomer base. MATERIALS AND METHODS. Ninety-six intact maxillary premolars were randomly divided into eight groups (n = 12). G1 (negative control) was the intact teeth. In Groups 2-8, root canal treatment with mesio-occlusodistal preparation was performed. G2 (positive control) was kept unrestored. The other groups were restored using composite resin as follows: G3, methacrylate-based composite (Z250); G4, methacrylate composite (Z250) with polyethylene fiber; G5 and G6, silorane-based composite (Filtek P90) without and with the fiber, respectively; G7 and G8, methacrylate-and silorane-based composite with nano-ionomer base, respectively. After aging period and thermocycling for 1000 cycles, fracture strength was tested and fracture patterns were inspected. The results were analyzed using ANOVA and Tukey HSD tests (${\alpha}$=0.05). RESULTS. Mean fracture resistance for the eight groups (in Newton) were G1: $1200{\pm}169^a$, G2: $360{\pm}93^b$, G3: $632{\pm}196^c$, G4: $692{\pm}195^c$, G5: $917{\pm}159^d$, G6: $1013{\pm}125^{ad}$, G7: $959{\pm}148^d$, G8: $947{\pm}105^d$ (different superscript letters revealed significant difference among groups). Most of the fractures in all the groups were restorable, except Group 3. CONCLUSION. Silorane-based composite revealed significantly higher strength of the restored premolars compared to that of methacrylate one. Fiber insertion demonstrated no additional effect on the strength of both composite restorations; however, it increased the prevalence of restorable fracture of methacrylate-based composite restored teeth. Using nano-ionomer base under methacrylate-based composite had a positive effect on fracture resistance and pattern. Only fiber-reinforced silorane composite restoration resulted in a strength similar to that of the intact teeth.