• 한국재료학회지
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• 제27권1호
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• pp.39-42
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• 2017

E-glass (electrical glass) fiber is the widely used as a reinforced composite material of PCBs (printed circuit boards). However, E-glass fiber is not stable because it has a dielectric constant of 6~7. On the other hand, D-glass (dielectric glass) fiber has a low dielectric constant of 3~4.5. Thus, it is adaptable for use as a reinforcing material of PCBs. In this study, we fabricated D-glass compositions with low dielectric constant, and measured the electrical and optical properties. In the glass composition, the boron content was changed from 9 to 31 wt%. To confirm the dependence of the dielectric constant on melting properties, D-glass with 22 wt% boron was melted at $1550^{\circ}C$ and $1650^{\circ}C$ for 2hrs. The glass melted at $1650^{\circ}C$ had a lower dielectric constant than the glass melted at $1550^{\circ}C$. Therefore, the D-glass with boron of 9~31 wt% was fabricated by melting at $1650^{\circ}C$ for 2hrs, and transparent clear glass was obtained. We identified the non-crystalline nature of the glass using an XRD (x-ray diffractometer) graph. The visible light transmittance values depending on the boron contents were measured and found to be 88.6 % ~ 82.5 %. Finally, the dielectric constant of the D-glass with 31 wt% boron was found to have decreased from 4.18 to 3.93.

• 비파괴검사학회지
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• 제33권5호
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• pp.430-435
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• 2013

본 연구에서는 유리섬유강화 복합재료 가스실린더의 복합재료의 파괴시 발생하는 음향방출신호의 특성을 살펴보기 위하여 실린더의 외부를 감싸고 있는 복합재료를 유리섬유묶음과 시편으로 가공하여 파괴시험을 실시하였다. 유리섬유묶음에 칼날을 압입하여 유리섬유가 파괴될 때 발생한 음향방출 신호의 진폭은 칼날의 절단각도가 커짐에 따라 유리섬유의 절단면이 증가되어 음향방출신호의 진폭이 증가되는 것으로 판단된다. 또한 복합재료 시편파괴시 감긴방향 파괴는 수직방향 파괴에 비해 hit 수는 적지만 섬유 절단각이 커짐에 따라 진폭은 높게 나타났다. 섬유감긴방향으로 시편파괴시 신호문턱값을 32 dB로 설정했을 경우는 40 dB로 설정했을 때는 나타나지 않았던 기지파괴 신호가 급격하게 나타나는 것으로 보아 기지파괴시 신호진폭은 40 dB 이하이고 유리섬유 파괴신호의 진폭은 40 dB이상 임을 알 수 있었다. 음향방출 신호의 진폭기울기는 음향방출원과 관련이 있으며, 섬유감긴방향으로 칼날을 압입했을 때 그 기울기는 0.08이고 수직방향일 때는 0.16로 구분되었다. 특히 수직방향 파괴의 경우 유리섬유묶음의 절단시 나타나는 진폭 기울기와 유사하여 시편의 수직방향파괴시 발생하는 신호의 주 음향방출원은 유리섬유파괴로 추정할 수 있다.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.35-41
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• 2017

The use of engineering plastics in automotive components is increasing with the trend towards improving the car strength and reducing weight. Among the different choices of materials, engineering plastic emerged as the necessary material for achieving lower costs, reduced weight and improved production efficiency. To produce the automotive parts, it is important to predict defect and validation of injection molding prior to design. Injection molding analysis and structural analysis are widely applied as a part of the design process when developing automotive parts. Injection molding analysis, in particular, involves a highly complicated mechanism that requires deep knowledge of polymer properties as well as an analytic approach different from that used for a general isotropic material when the molded material is used as a structural material. This is because the parts made of polymer have pre-stress factors such as intrinsic deformation and residual stress. The most important factors for injection molded plastic products are injection molding condition and cavity design, taking into account ease of molding, mass production and application. Despite optimal injection molding conditions and cavity design, however, glass fiber orientation is critically linked to strength reduction. The application of injection molding and structural coupled analysis provides a low-cost solution for product molding and structural validation, all prior to the actual molding. The purpose of this study involves the validation, pre-study, and solution of defect in injection-molded polymer automotive parts using the simulation software for injection molding and structural coupled analysis. Finally, this thesis provides validation of an injection molding and structural coupled analytic mechanism that can demonstrate the effect of glass fiber orientation on mechanical strength. Design improvement ideas for the injection molded product of PPS (Poly Phenylene Sulfide)+40% glass fiber are also suggested.

• 한국전산유체공학회지
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• 제16권1호
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• pp.22-29
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• 2011

In this study, the glass fiber drawing from a silica preform in the furnace for the optical fiber manufacturing process is numerically simulated by considering the radiative heating of cylindrically shaped preform. The one-dimensional governing equations of the mass, momentum, and energy conservation for the heated and softened preform are solved as a set of the boundary value problems along with the radiative transfer approximation between the muffle tube and the deformed preform shape, while the furnace heating is modeled by prescribing the temperature distribution of muffle tube. The temperature-dependent viscosity of silica plays an important role in formation of preform neck-down profile when the glass fiber is drawn at high speed. The calculated neck-down profile of preform and the draw tension are found to be reasonable and comparable to the actual results observed in the optical fiber industry. This paper also presents the effects of key operating parameters such as the muffle tube temperature distribution and the fiber drawing speed on the preform neck-down profile and the draw tension. Draw tension varies drastically even with the small change of furnace heating conditions such as maximum heating temperature and heating width, and the fine adjustment of furnace heating is required in order to maintain the appropriate draw tension of 100~200 g.

• Journal of the Korean Wood Science and Technology
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• 제41권1호
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• pp.51-57
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• 2013

직물형 유리섬유 조합에 따른 보강 집성재의 볼트 접합부 전단 성능을 알아보기 위하여 인장형 전단시험을 실시하였다. 보강재는 직물형 유리섬유로서 유리섬유 배열 형태는 평직형과 능직형을 사용하였다. 보강 집성재는 5층으로 직물형 유리섬유의 삽입 위치와 조합 형태를 달리하여 층재 사이에 삽입 적층시켜 제작하였다. 인장형 전단 시험편은 강판 삽입형로서 끝면거리 7D에 직경 12, 16 mm의 볼트로 접합하였다. 체적비 1% 직물형 유리섬유 보강 집성재의 경우 12 mm 볼트 접합부의 항복 전단내력은 집성재 외층부보다 내층부를 보강한 시험편에서 10% 큰 값을 나타내었다. 체적비 2% 직물형 유리섬유 보강 집성재의 항복 전단내력은 12 mm 볼트 접합부의 경우 각층재 사이에 삽입 적층시킨 시험편이 보강하지 않은 접합부보다 약 22% 향상되었으며, 16 mm 볼트 접합부의 항복 전단내력은 약 20% 향상되었다.

• 대한치과보철학회지
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• 제42권3호
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• pp.280-293
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• 2004

Statement of problem. Glass fiber post is one of recent developments to accommodate esthetic restoration for endodontically treated teeth. This has many advantages over conventional post system in physical properties, esthetic factor, risk of root and restoration fracture, adhesion to core, radiopacity, removal and retrievabilty, biocompatibility and chemical stability. Purpose. This in vitro study was to evaluate the most suitable type of resin core for the glass fiber post through surveying the fracture modes and the maximum load that fractures the tooth. Material and methods. 50 sound maxillary premolars restored with glass fiber posts($ParaPost^{(R)}$ Fiber White) and different types of resin cores(ParaCore, $Z100^{TM}$, $Rebilda^{(R)}$ and $Admira^{(R)}$) were prepared and loaded to faiure in a universal test machine. The maximum fracture load and fracture mode were investigated in the specimens that were restored with resin and those of metal cast and core. With the data, Wilcoxon rank sum test was used to validate the significance between the test groups, and Tukey' s studentized range test was used to check if there is any significant statistical difference between each test group. Every analysis was approved with 95% reliance. Results. On measuring the maximum fracture load of teeth specimens, there was a significant difference between the maximum fracture loads of the tooth specimens. ParaCore showed the highest mean maximum fracture load followed by $Z100^{TM}$. And, the distribution of fracture mode of tooth specimens showed generally Type D, the three parted fracture of the core around the post was mostly seen(62.5%), and specifically, ParaCore showed 90% and $Z100^{TM}$ showed 100% Type D fracture. Conclusion. Referring to the values of maximum fracture load and mean compressive fracture load, ParaCore and $Z100^{TM}$ had high values and are recommended as tooth colored resin core material for glass fiber post. CLINICAL IMPLICATIONS. This study was carried out intending to be of aid in selecting the appropriate resin core for the glass fiber post. The dual cure type composite resin ParaCore and light cure type composite resin $Z100^{TM}$ have good properties and are recommended as tooth colored resin core material for glass fiber post.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1322-1325
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• 2005

The main objectives of this research work are to develop conductive glass fiber woven roving and carbon fiber unidirectional fabric composite materials and to determine their electromagnetic shielding effectiveness(EMSE). Epoxy is the matrix phase and glass, carbon fiber are the reinforcement phase of the composite material. Carbon black are incorporated as conductive fillers to provide the electromagnetic shielding properties of the composite material. The amount of carbon black in the composite material is varied by changing the carbon black composition, woven roving and unidirectional (fabric) structure. The EMSE of various fabric composites is measured in the frequency range from 300MHz to 800MHz. The variations of EMSE of woven roving and unidirectional composites with fabric structure, metal powder composite are described. Suitability of conductive fabric composites for electromagnetic shielding applications is also discussed.

• 한국전산유체공학회지
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• 제18권4호
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• pp.69-73
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• 2013

Mass manufacturing of optical fiber includes the process of very thin glass fiber drawing by heating and softening the high purity silica preform and applying the draw tension on the softened tip of preform neck-down profile in a draw furnace. In this computational study, this process is numerically modeled with simplified geometry of the draw furnace which is comprised of essential parts such as concentric graphite heater, muffle tube, and insulation surrounding the heater. The iterative computational scheme is employed between one-dimensional model of neck-down profile prediction and two-dimensional axisymmetric thermo-fluid CFD computation of radiative heating and working gas convection. The computational results show the experimentally observed neck-down profile in heated section of preform, while yielding the reasonable values of draw tension and heater wattage. Also, this study analyzes and discusses the effects of heating conditions such as heater length and temperature on several important aspects of glass fiber drawing process.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.609-614
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• 1997

Recently, many researchers have performed R&D about strengthening of R/C with steel plates, carbon fiber sheets. aramid fiber sheets and glass fiber sheets, and so on. However most of research were limited in study of flexural strengthening of R/C beams. This paper shows the results of an experimental study on shear reinforcement of deep beams using Glass Fiber Sheet in relation to shear-span ratio. strengthening orientation and anchorage. The results prove that shear failure is governed by reinforced orientation. adherence and anchorage. Additional anchorage of fibers does not only cause the improvement in the internal resistance, but also control the brittle shear failure of specimen after reaching the maximum load.

• Advances in concrete construction
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• 제6권1호
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• pp.29-45
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• 2018

This paper investigates the effect of inclusion of glass fibers on mechanical and fracture properties of binary blend geopolymer concrete produced by using fly ash and ground granulated blast furnace slag. To study the effect of glass fibers, the mix design parameters like binder content, alkaline solution/binder ratio, sodium hydroxide concentration and aggregate grading were kept constant. Four different volume fractions (0.1%, 0.2%, 0.3% and 0.4%) and two different lengths (6 mm, 13 mm) of glass fibers were considered in the present study. Three different notch-depth ratios (0.1, 0.2, and 0.3) were considered for determining the fracture properties. The test results indicated that the addition of glass fibers improved the flexural strength, split tensile strength, fracture energy, critical stress intensity factor and critical crack mouth opening displacement of geopolymer concrete. 13 mm fibers are found to be more effective than 6 mm fibers and the optimum dosage of glass fibers was found to be 0.3% (by volume of concrete). The study shows the enormous potential of glass fiber reinforced geopolymer concrete in structural applications.