• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.639-644
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• 2000

Prestressing steels are susceptible to corrosion, which is considered the major reason in the deterioration of prestressed concrete structures. To solve this problem, many research have been made to utilize new type of tendons. FRP tendons have many advantages compared to steel tendons. However, FRP tendons have some disadvantages, such as no plastic behavior. This study focused on the flexural behavior of prestresssed concrete beams which is fabricated by post-tensioning method with CFRP (Carbon Fiber Reinforced Plastic) tendons. Th results drawn from the study, prestressed concrete beams with CFRP tendons have higher flexural cracking load, flexural yielding load, and flexural fracture load. While displacement at the fracture stage is lower compared to prestressed concrete beams with steel tendon. Excessive steel reinforcement lead lower ductility index. So, appropriate reinforcement guideline is needed. Further more, prestressed concrete beams with CFRP tendons can have sufficient ductility index when ruptured by crushing of concrete or used unbonded tendon. Therefore, the best design method for prestressed concrete beams with CFRP tendons is over-reinforcement, and use of unbonded tendon.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.6
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• pp.439-445
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• 2016

Carbon fiber reinforced plastic (CFRP) composites have been widely used due to their great strength, stiffness and light weight. However, due to its anisotropy and inhomogeneous properties the machining process of CFRP composites is typically more complex than that of regular metals. Since there are many defects, such as delamination and tool wear during the machining process of CFRP composites, the optimization of this process is essential in improving the productivity. In this study, orthogonal machining of CFRP composites was performed to identify the machining characteristics of these materials. In addition, an experimental observation of delamination was investigated through the use of scanning electron microscopy (SEM). In these experiments, the cutting forces were measured and analyzed to determine the difference between machining of CFRP composites and metals. The comparison between the numerical models and experimental results was performed in terms of the maximum cutting forces.

• Journal of Power System Engineering
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• v.18 no.4
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• pp.78-84
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• 2014

The estimation of deformation and strain for the twill-weave carbon fiber reinforced plastic composite(CFRP) during the test with a digital image correlation system were implemented experimentally. The carbon fiber reinforced plastic composites have been developed as the edge technology materials. The plain, twill and satin weave types are commonly used for the CFRP composites. Thus, it is essential to find the deformation characteristics for those types of CFRP more easily. Especially the DIC method can express the visual strain distributions at the full range of the interested areas in the structures. In this study, the mechanical properties of twill-weave CFRP composite and the variation of strains in a full field of the specimen were estimated. The experiments were performed under a tensile loading and 3-point bending test with strain gages. Futhermore the DIC deformation results were estimated for the comparison. The results showed the deformation and strain contours visually well in all region of the interested areas and so usefulness for the safety control of the structures.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.3
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• pp.8-13
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• 2020

Carbon fiber-reinforced plastics (CFRPs) are extremely strong and light fiber-reinforced plastics containing carbon fibers. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and rigidity are required, such as in the aerospace, automotive, and ship superstructure industries. In CFRP drilling, the tool performance greatly varies depending on the tool shapes, cutting conditions, and diamond coating. This study developed a new type of tungsten carbide drill with multi-blade edges to evaluate the surface quality of CFRP materials according to the coating thickness of diamond-coated drills. Experiments on tool wear, surface roughness, and burr formation were conducted. The bore exit quality of a 12 mμ -coated drill was better than that of a 6 mμ -coated drill. The superior effects of the 12 mμ -coated drill and the good surface quality of CFRP were also demonstrated.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.4
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• pp.402-410
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• 1996

Recently carbon fiber reinforced plastic(CFRP) has been used structural materials in corrosive environment such as for water, chemical tank and chemical pipes. However, mechanical properties of such materials may change when CFRP are exposed to corrosive environment for long periods of time. Therefore, it is important to understand the effect of moisture absorption on mechanical properties of the CFRP. In this study, degradation behavior of immersed carbon fiber/epoxy resin composite material was investigated using acoustic emission(AE) technique. Fracture toughness test are performed on the compact tension(CT) test specimens that are pilled by two types of laminates $[0^{\circ}_2$/$90^{\circ}_2]_3s$ and $[0^{\circ}_2$/$90^{\circ}_2]_6s$During the fracture toughness test, AE test was carried out to monitor the damage of CFRP by moisture absorption. In spite of the change of moisture absorption rate, the fracture toughness of CFRP was not change. As immersion time increased, AE event count numbers decreased in low amplitude range of AE for amplitude distribution histogram. The event in low amplitude range was known to be generated by debonding of matrix-fiber interface. Therefore, decrease of AE event count numbers in low amplitude range represents that debonding of matrix-fiber interface which was probably generated by moisture absorption.

• Journal of Korean Association for Spatial Structures
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• v.5 no.2 s.16
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• pp.65-71
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• 2005

The reinforced concrete becomes deteriorated. In strengthening of reinforced concrete structure, it is recently useing FRP. In research, flexural strengthening of reinforced concrete beam can be Efficient design. But shear srengthening og reinforced concrte beam can't be Efficient design by variable cause. The purpose of this study is to investigate the shear resisting effect of filling-up CFRP in reinforced concrete beams with web reinforced. Ten specimens were manufactured and tested. In the test result, it was analysis. The main variables in the test were a space of web reinforcement and a direction of CFRP.

• Applied Chemistry for Engineering
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• v.34 no.5
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• pp.515-521
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• 2023

In this study, waste carbon fiber obtained by pyrolysis of carbon fiber reinforced plastic (CFRP) was used to produce carbon fluoride through vapor phase fluorination and recycled as a reducing electrode material for lithium primary batteries. First, the physicochemical properties of the waste carbon fiber obtained by pyrolysis were determined, and the structural and chemical properties of carbon fluoride were analyzed to evaluate the effect of vapor phase fluorination on the waste carbon fiber. XRD analysis confirmed that the hexagonal network carbon laminated structure (002 peak) of the waste carbon fiber was gradually converted into a carbon fluoride structure (CF_X, 001 peak) as the temperature of gas phase fluorination increased. The discharge capacity of the lithium primary battery produced using this carbon fluoride was up to 862 mAh/g. This was compared to the discharge capacity of carbon fluoride-based Li-ion batteries made of other carbon materials. These results suggest that carbon fluoride made from waste CFRP-based carbon fibers can be used as a reducing electrode material for Li-ion batteries.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1078-1085
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• 2022

Fouling organisms attached to a ship not only greatly increase the resistance of the ship as they grow on the hull but also cause disturbances in local marine ecosystems as they move with the ship. Accordingly, the International Maritime Organization has started discussing the removal of biofouling and evaluation of cleaning performance to prevent the migration of hull-fouling species. In this study, specimens of FRP(Fiber Reinforced Plastic), HDPE(High Density Polyethylene), and CFRP(Carbon Fiber Reinforced Plastic) materials used for small ship construction were cured in Gyeokpo Port (Jeonlakbuk-do) for about 80 days. Then, attached organism removal experiments were performed using a water jet nozzle. The results show that seaweeds, such as laver, were removed when the distance between the nozzle and the specimen was 1.8 cm and the pressure was 100 bar. Furthermore, it was confirmed that the cleaning of barnacles was possible only when the pressure was 200 bar or more.

• Composites Research
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• v.29 no.6
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• pp.342-346
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• 2016

Carbon fiber reinforced plastic (CFRP), one of lightweight materials, is the fiber structure using carbon fiber. It is the composite material that has the characteristics of carbon and plastic. As for the fiber structure, it has the great strength due to fiber direction. CFRP for woven type is used mostly as such a CFRP with lightweight. Woven type is more stable when compared with unidirectional type. On the other hand, woven type is highly priced. Therefore, this study aims to analyze the fiber structure of unidirectional CFRP. In this study, as the stacking angle [0/X/-X/0], X is the variable. This is unidirectional CFRP in which the angle phase of X has been reversed and stacked. By using such a unidirectional CFRP, the analysis model which had a crack at the center as the form of panel with the thickness of 2 mm was used. On analysis, the load is applied on the upper and lower parts being connected with a pin. The damage in the area near center crack was investigated. As for the analysis model, 3D surface model was designed by using CATIA. For CFRP stacking, the stacking direction was determined by using ACP in ANSYS program and the analysis model with two stacks was made. Afterwards, the structural analysis was carried out.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.3
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• pp.589-596
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• 2018

Transportation or structure has the important role at clothing, food, and housing at modern society. If even the small crack happens and propagates at transportation or structure, the parts are fractured and they can cause a disaster. CT specimen was used in order to investigate the damage trend due to the crack propagation at this study to prevent this situation. As the material of CT specimen, the unidirectional carbon fiber reinforced plastic of the composite material in the limelight nowadays. The laminate angle designated in order of [60/-60/60/-60] was applied to the specimen model with the unidirectional fiber. As the analysis condition, the forced displacement was applied to the hole of upper part after fixing the hole of lower part. At the result of this study, the equivalent stress and shear stress was shown to be higher in order of the structural steel, copper, titanium and aluminum. This study result is thought to be utilized usefully at verifying the damage of CT specimen made of inhomogeneous material.