• 한국기계가공학회지
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• 제21권9호
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• pp.12-20
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• 2022

Delamination and burr defects are important problems in drilling fiber reinforced plastics. A method for measuring FRP drilling defects has been studied. Delamination and burr factors were defined as the relative length or area. Using these factors, the effects of tool shape and drilling conditions on delamination and burr were studied. In this study, the defects that occur when drilling a glass-carbon fiber hybrid composite were compared in terms of three factors. In the glass-carbon fiber hybrid composite, the effects of the feed rate and tool point angle on the delamination and burr factors were similar to those in previous studies. The diameter of the tool did not affect the defect factor. A circular burr was generated in a drill tool with a point angle of 184°, and a relatively small deburring factor was observed compared with a tool with a point angle of 140°.

• 한국기계가공학회지
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• 제16권5호
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• pp.157-165
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• 2017

The high-pressure resin transfer molding (HP-RTM) technology has been commercialized for fast production of fiber reinforced composite materials. The high-pressure mixing head was one of the most core component of the HP-RTM process. In this study, a mixing head was systematically designed, manufactured and evaluated. This mixing head was composed of a nozzle, a mixing chamber, a cleaning piston part, and an internal mold release part. In actual, a straight-type structure was newly designed instead of the conventional L-type structure for improving the maximum mixing pressure and mixing ratio precision. The performance of mixing head was showed maximum mixing pressure of 15.22MPa and mixing ratio precision of 0.12%. CFRP molding experiments were successfully obtained a 6~11 laminating carbon sheet using HP-RTM presses and specimen molds.

• 대한기계학회논문집A
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• 제26권3호
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• pp.553-559
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• 2002

Carbon-fiber which has very small radial dimension makes us difficult to measure it's properties. So in this paper, we suggest a simple method to measure the thermal conductivity of a carbon-fiber's and carbon-fiber-reinforced-plastics(CFRP) laminates. The thermal conductivity of CFRP laminates was measured experimentally at the same time analytically. The experimental model is based on the one-dimensional analysis of fin sample because CFRP laminates has a thin geometric configuration. The analytical model to measure the thermal conductivity of carbon-fiber is expressed by use of mean-field model which is based on Eshelby's elliptical inclusion problem. Therefore the thermal conductivity of angle-ply laminates can be computed by use of effective longitudinal and transverse thermal conductivities of unidirectional composite of the constituents.

• Tribology and Lubricants
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• 제36권3호
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• pp.133-138
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• 2020

In this paper, we present an experimental investigation of the friction coefficient and wear area change of carbon/epoxy and E-glass/epoxy composites depending on the fiber direction (0°/90°). We compared the results of the case where the sliding direction is parallel to the fiber direction (0°) with that of the case where it is perpendicular to the fiber direction (90°). The ball-on-plate wear test equipment was used to cause wear in both directions. Two types of specimens were prepared with thicknesses of 3 mm-one made of carbon fiber reinforced plastic composite (CFRP) and the other of glass fiber reinforced plastic composite (GFRP). A normal force of 20 N was applied to the specimen and the sliding speed was 10 mm/s and the sliding distance was set to 20 m to perform the wear test. The CFRP demonstrates superior tribological characteristics compared to the GFRP. This outcome is attributed to graphitization of carbon, which serves as solid lubricating particles. In addition, both CFRP and GFRP are worn more in the 90° direction than in the 0° direction. This is due to the greater occurrence of fiber breakage and separation in the 90° direction than in the 0° direction. This study is expected to be utilized as basic data for understanding the friction and wear characteristics of CFRP and GFRP composites along the fiber direction and to apply the appropriate material.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.180-183
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• 2001

Glass fiber reinforced plastic(CFHP) tent pole fabricated by the pultrusion process with unidirectional glass fiber is two times as heavy as aluminum tent pole owing to the low specific modulus The first objective of this research is the design the high strength and light weight tent pole compete with. the second is the develope glass fiber carbon fiber hybrid tent pole pultrusion process. the third is the evaluate the mechanical properties of the hybrid tent pole compare to these of the duralumin tent pole.

• Carbon letters
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• 제17권1호
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• pp.33-38
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• 2016

In the present study, exfoliated graphite nanoplatelets (xGnP) with different particle sizes were coated onto polyacrylonitrile-based carbon fibers by a direct coating method. The flexural properties, interlaminar shear strength, and the morphology of the xGnP-coated carbon fiber/phenolic matrix composites were investigated in terms of their longitudinal flexural strength and modulus, interlaminar shear strength, and by optical and scanning electron microscopic observations. The results were compared with a phenolic matrix composite counterpart prepared without xGnP. The flexural properties and interlaminar shear strength of the xGnP-coated carbon fiber/phenolic matrix composites were found to be higher than those of the uncoated composite. The flexural and interlaminar shear strengths were affected by the particle size of the xGnP, while the particle size had no significant effect on the flexural modulus. It seems that the interfacial contacts between the xGnP-coated carbon fibers and the phenolic matrix play a role in enhancing the flexural strength as well as the interlaminar shear strength of the composites.

• Steel and Composite Structures
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• 제24권4호
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• pp.383-390
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• 2017

This paper highlights the experimental and numerical investigations performed on a tubular T-joint fabricated from circular hollow sections under axial compressive loads applied at the brace. Tests were performed on a reference joint and the joint wrapped with Carbon Fiber Reinforced Polymer (CFRP). The Nitowrap EP carbon fiber with Nitowrap 410 resin serve as a composite material is used for wrapping the T-joint. Schematic diagram of the fabricated tubular joint for the experimental test setup, along with the experimental and numerical results are presented. After performing these experiments, it has been demonstrated that the joint wrapped with CFRP has a better strength and lesser deflection than a reference joint. Finite element analysis carried out in Ansys reveals that the results were in good correlation with the experimental values.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.408-410
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• 2012

본 연구에서는 수지 인장시편과 스트랜드 인장시편을 적용하여 탄소섬유/에폭시 복합재의 고온에서의 특성을 조사하였다. 연구결과에 따르면 수지시편의 인장강성은 수지의 유리전이 온도에 근접해감에 따라 서서히 감소하지만 스트랜드 인장시편의 인장강성은 상온에서의 인장강성을 유지한다. 수지시편과 스트랜드 시편의 인장강도는 온도가 유리전이 온도에 근접할수록 급격한 감소를 나타내었다.

• 한국안전학회지
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• 제34권6호
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• pp.1-6
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• 2019

Carbon fiber has excellent specific strength, corrosion resistance and heat resistance. And p-Aramid fiber has high toughness and heat resistance and high elasticity, and is used in various fields such as industrial protective materials, bulletproof helmets and vests, as well as industrial fields. However, carbon fiber is relatively expensive, and is susceptible to brittle fracture behavior due to its low fracture strain. On the other hand, the aramid fiber tends to decrease in elastic modulus and strength when applied to the epoxy matrix, but it is inexpensive and has higher elongation and fracture toughness than carbon fiber. Thus the twill hybrid carbonaramid fiber reinforced composite laminate composite was investigated for a delamination fracture toughness under Mode I loading by 2 kinds of MBT and MCC deduction. The specimen was fabricated with 20 hybrid fabric plies. The initial crack was made by inserting the teflon tape in the center plane with a₀/W=0.5 length. The results show that SERR(Strain Energy Release Rate) as the critical and stable delamination fracture toughness were 0.09 kJ/㎡, 0.386 kJ/㎡ by MBT deduction, and 0.192 kJ/㎡, 0.67 kJ/㎡ by MCC deduction, respectively.

• Steel and Composite Structures
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• 제34권2호
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• pp.299-308
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• 2020

This study aims to carry out the experimental and numerical investigation on the flexural behavior of sandwich honeycomb composite (SHC) beams reinforced with novel triaxially woven fabric composite skins. Different stacking sequences of the carbon fiber reinforcement polymer (CFRP) laminate; i.e., 0°-direction of TW (TW0), 0°-direction of UD (UD0), and 90°-direction of UD (UD90) were studied, from which the flexural behavior of SHC beam behaviors reinforced with TW0/UD0 or TW0/UD90 novel laminated skins were compared with those reinforced with UD0/90 conventional laminated skins under four-point loading. Generally, TW0/UD0 SHC beams displayed the same flexural stiffness as UD0/90 SHC beams in terms of load-deflection relationships. In contrast, TW0/UD90 SHC beams showed a 70% lower efficiency than those of UD0/90 SHC. Hence, the TW0/UD0 laminate arrangement is more effective with a mass reduction of 39% compared with UD0/90 for SHC beams, although their stiffness and shear strength are practically identical.