• 한국재료학회지
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• 제20권3호
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• pp.148-154
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• 2010

It is necessary to develop new methods to prevent catastrophic failure of structural material in order to avoid accidents and conserve natural and energy resources. Design of intelligent materials with a self-diagnosing function to prevent fatal fracture of structural materials was achieved by smart composites consisting of carbon fiber tows or carbon powders with a small value of ultimate elongation and glass fiber tows with a large value of ultimate elongation. The changes in electrical resistance of CF-GFRP/GFRP (carbon fiber and glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased abruptly with increasing strain, and a tremendous change was seen at the transition point where carbon fiber tows were broken. Therefore, the composites were not to monitor damage from the early stage. On the other hand, the change in electrical resistance of CP-GFRP/GFRP (carbon powder dispersed in glass fiber-reinforced plastics/glass fiber-reinforced plastics) composites increased almost linearly in proportion to strain. CP-GFRP/GFRP composites are superior to CF-GFRP/GFRP composites in terms of their capability to monitor damage by measuring change in electrical resistance from the early stage of damage. However, the former was inferior to the latter as an application because of the difficulties of mass production and high cost. A method based on monitoring damage by measuring changes in the electrical resistance of structural materials is promising for improved reliability of the material.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2001년도 추계학술대회(한국공작기계학회)
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• pp.155-160
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• 2001

In the use of glass fiber reinforced plastics(GFRP) it is often necessary to cut the components, but the cutting of GFRP is often made difficult by the delamination of the compositions and short tool life. Experimental investigation was conducted to evaluate the chip formation of the glass fiber reinforced plastics during orthogonal cutting. The chip formation process, cutting force, and thrust force were studied. The chip formation processes were studied through the use of quick-stop device. Chip-tool contact areas were obtained with the use of the quick-stop device, and observed using optical microscopy after polishing. Cutting force and thrust force were measured through the use of the tool dynamometer.

• 콘크리트학회지
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• 제10권4호
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• pp.101-111
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• 1998

본 논문의 목적은 전단내력이 부족한 R/C보에 CFS(Carbon Fiber Sheets), CFRP(Carbon Fiber Reinforced Plastic), GFRP(Glass Fiber Reinforced Plastics)를 이용해 전단보강을 할 경우에 보의 역학적 거동특성을 규명하기 위한 것이다. 본 논문의 목적을 달성하기 위하여 총 19개의 시험체가 제작되었으며, 실험변수로는 전단스팬비, 보강재료, 보강방법, 보강간격 및 방향을 산정하였다. 본 논문의 실험결과, FRP를 이용해 전단내력이 부족한 R/C보에 보강을 하였을 경우 약 50~70%정도의 보강효과를 나타내었다. 또한 소성이론에 근거한 철근콘크리트보의 전단강도 예측모델을 개발하였고 실험치와의 비교를 통해 개발된 모델의 적합성을 검증하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.7-11
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• 2000

In this paper was studied on the mechanical characteristics of Glass Fiber Reinforced Plastics(GFRP) of the steel bar it is to replace. The advantage of FRP such as high strength, low weight and chemical inertness or noncorrosiveness can be fully exploited. GFRP bar were successfully fabricated at l0mm nominal diameters of solid and hollow types using a pultrusion method. Tensile and bending specimens from this bar were tested and compared with behavior of GFRP rebar and steel bar.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.199-205
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• 2001

This paper describes the design methodology, manufacturing process, rebar tensile and bending properties. Braidtrusion is a direct Composite fabrication technique utilizing an in-line braiding and pultrusion process. The produced Composite rebar exhibits ductile stress-strain behavior similar to that of conventional steel bar. Various rebar diameters ranging from modeling scale(3m) to full-scale prototype of 9.5mm have been produced Glass Fiber Reinforced Plastics(GFRP) rebar were successfully fabricated at $\phi$8.5mm and $\phi$9.5mm nominal diameters of soild and hollow type using a braidtrusion process. Tensile and bending specimens were tested and compared with behavior of stress-strain of GFRP rebar and steel bar.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1216-1224
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• 1996

In the use of glass fiber reinforced plastics it is often necessary to cutting the components, but the cutting GFRP is often made difficult by the delamination of composites and the short tool life. In this paper, the machinability of GFRP by mean of tool materials and type was experimentally investigated. By proper selection of cutting tool material and type excellent machining of this workpiece is achieved. The surface quality relate closely with the feed rate and cutting tools.

• 한국안전학회지
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• 제16권3호
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• pp.135-142
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• 2001

본 연구에서는 복합소재인 GFRP(Glass Fiber Reinforced Polyester)의 2차원 절삭공정에서 주파수 스팩트럼과 절삭 메커니즘과의 연관성에 관하여 논의한다. 해석방법으로는, 공정중 발생하는 절삭력 신호를 FFT에 의해 주파수 분석하고 주파수 스팩트럼과 다양한 칩형성 메커니즘과의 연관관계를 모델링한다. 특히, 섬유경사각(Fiber orientation angle), 절삭변수 그리고 공구형상이 절삭 메커니즘에 미치는 영향을 평가하였다.

• 대한치과교정학회지
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• 제45권3호
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• pp.130-135
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• 2015

Objective: In our previous study, glass-fiber-reinforced plastics (GFRPs) made from polycarbonate and glass fibers were prepared for esthetic orthodontic wires using pultrusion. These laboratory GFRP wires are more transparent than the commercially available nickel-titanium wire; however, an investigation of the color stability of GFRP during orthodontic treatment is needed. Accordingly, in the present study, the color stability of GFRP was assessed using colorimetry. Methods: Preparation of GFRP esthetic round wires (diameter: 0.45 mm [0.018 inch]) using pultrusion was described previously. Here, to investigate how the diameter of fiber reinforcement affects color stability, GFRPs were prepared by incorporating either $13-{\mu}m$ (GFRP-13) or $7-{\mu}m$ glass (GFRP-7) fibers. The color changes of GFRPs after 24 h, and following 1, 2, and 4 weeks of coffee immersion at $37^{\circ}C$, were measured by colorimetry. We evaluated the color stability of GFRPs by two evaluating units: the color difference (${\Delta}E^*$) and National Bureau of Standards (NBS). Results: After immersion, both GFRPs showed almost no visible color change. According to the colorimetry measurements, the ${\Delta}E^*$ values of GFRP-13 and GFRP-7 were 0.73-1.16, and 0.62-1.10, respectively. In accordance with NBS units, both GFRPs showed "slight" color changes. As a result, there were no significant differences in the ${\Delta}E^*$ values or NBS units for GFRP-13 or GFRP-7. Moreover, for both GFRPs, no significant differences were observed in any of the immersion periods. Conclusions: Our findings suggest that the GFRPs will maintain high color stability during orthodontic treatment, and are an attractive prospect as esthetic orthodontic wires.

• International Journal of Safety
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• 제3권1호
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• pp.1-5
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• 2004

This study discusses frequency analysis based on autoregressive (AR) time series model, and the characterization of surface quality in orthogonal cutting of a fiber-matrix composite materials. A sparsely distributed idealized composite material, namely a glass reinforced polyester (GFRP) was used as workpiece. Analysis method employs a force sensor and the signals from the sensor are processed using AR time series model. The experimental correlations between the fiber pull-out and AR model coefficients are then established.

• 대한기계학회논문집A
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• 제20권11호
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• pp.3433-3440
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• 1996

This paper was investigation of the stres corrosion cracking(SCC) mechanism and the properties of corrosion fracture surface of glass fiber reinforced plastics(GFRP) produced by hand lay up(HLU) method in synthetic sea water. Test material is GFRP, that was used vinylester type epoxy acrylate resin and an unsaturated polyester as the matrix and the chopped strand mat(CSM) type E-glss fiber as the reinforcement. The slow strain rate test(SSRT) was performed on dry, wet and saturated wet specimens in sea water. Here the pH concentration of synthetic sea water was 8.2 and the strain rate is 1 x $10^{-6}$($sec^{-1}$) and test temperature ranges varied from $-60^{\circ}C$ to $80^{\circ}C$. It could be confirmed the fact that wet specimens tested at a particular test temperature ranges were appeared the eviences of SCC such as con-planar, mirror and hackle zone. Moreover, SCC of GFRP in sea water was characterised by falt fracture surfaces with only small amounts of fiber pull-out, in partial.