• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.155-156
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• 2012

• Structural Engineering and Mechanics
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• v.18 no.1
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• pp.21-40
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• 2004

In this paper, we modify the L-L model (Li et al. 2003) and extend the application of this model to concrete confined by both steel reinforcement and CFRP. Thirty-six concrete cylinders with a dimension of ${\varphi}30{\times}60$ cm were tested to verify the effectiveness of the proposed model. The experimental test results show that different types of steel reinforcement have a great effect on the compressive strength of concrete cylinders confined by steel reinforcement, but the different types of steel reinforcement have very little effect on concrete cylinders confined by both steel reinforcement and CFRP. Compared with the stress-strain curves of confined concrete cylinders, we can conclude that the proposed model can provide more effective prediction than others models.

• Design & Manufacturing
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• v.16 no.2
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• pp.1-6
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• 2022

As environmental regulations are strengthened, automobile manufacturers continuously research lightweight structures based on carbon fiber reinforced plastic (CFRP). However, it is difficult to see the effect of strength reinforcement when using a single CFRP material. To improve this, a hybrid laminate in which CFRP is mixed with the existing body structural steel was proposed. In this paper, CFRP patch reinforcement is applied to each compression/tensile action surface of a 22MnB5 metal sheet, and it was evaluated through a 3-point bending experiment. Progressive failure was observed in similar deflection on bending deformation to each one-sided reinforced specimen. After progressive failure, the tensile reinforced specimen was confirmed to separate the damaged CFRP patch and 22MnB5 sheet from the center of the flexure. The compression reinforced specimen didn't separate that CFRP patch and 22MnB5, and the strength reinforcement behavior was confirmed. In the compression reinforced specimen, damaged CFRP patches were observed at the center of flexure during bending deformation. As a result of checking the specimen of the compression reinforcement specimen with an optical microscope, It is confirmed that the damaged CFRP patch and the reinforced CFRP patch overlapped, resulting in a concentrated load. Through the experimental results, the 22MnB5 strength reinforcement characteristics according to the reinforcement position of the CFRP patch were confirmed.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.377-385
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• 2003

Flexural characteristics of the R.C beams strengthened with newly-developed grid-type carbon fiber plastics(CFRP-GRIDS) were investigated. The tests were conducted under the four-points load to the failure to investigate the strengthening effects of CFRP-GRIDS on the beams. Results showed that initial cracks appeared in the boundary layers of fibers embedded in the newly-placed mortar concrete slowly progressed to the direction of supports and showed fracture of fiber plastics and brittle failure of concrete in compression in sequence after the yielding of steel reinforcement. Accordingly, the appropriate area of Grid-type carbon-fiber plastics in the strengthening design of deteriorated RC structures should be limited and given based on the ultimate strength design method to avoid the brittle failure of concrete structures.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.8
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• pp.122-128
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• 2001

The objective of the present study was to investigate the characteristics of the friction and wear according to the amount of ion-irradiation for the carbon fiber reinforced plastic(CFRP). Unidirectional carbon fiber reinforced composites were fabricated with epoxy resin as a matrix and carbon fiber as a reinforcement, and its surface was modified by the ion-assisted reaction. When the amount of ion-irradiation was $1{\times}10^{16}$ ions/$cm^2$, the friction coefficients of composites were about 0.1 and the wear mode was stable, whereas, the friction coefficient of non-treatment composites were about 0.16 and the wear mode was very unstable. But if the amount of ion-irradiation was $5{\times}10^{16}$ ions/$cm^2$, the friction coefficients were higher rather than that of $1{\times}10^{16}$ ions/$cm^2$. Consequently, the amount of ion-irradiation was not in proportion to the friction coefficients, and it was conformed that the optimal conditions would exist between broth of them.

• Tribology and Lubricants
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• v.18 no.1
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• pp.61-67
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• 2002

The objective of the present study was to investigate the characteristics of the friction and wear according to the amount of ion-irradiation for the carbon fiber reinforced plastic (CFRP). Unidirectional carbon fiber reinforced composites were fabricated with epoxy resin as a matrix and carbon fiber as a reinforcement, and its surface was modified by the ion-assisted reaction. When the amount of ion-irradiation was $1{\times}10^{16}$ $ions/cm^{2}$. the friction coefficients of composites were about 0.1 and the wear mode was stable. whereas, the friction coefficient of non-treatment composites were about 0.16 and the wear mode was very unstable. But if the amount of ion-irradiation was $5{\times}10^{16}$ $ions/cm^{2}$, the friction coefficients were higher rather than that of $1{\times}10^{16}$ $ions/cm^{2}$ Consequently. the amount of ion-irradiation was not in proportion to the friction coefficients, and it was conformed that the optimal conditions would exist between both of them.

• Composites Research
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• v.34 no.1
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• pp.35-46
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• 2021

This paper aims to reduce weight by replacing the reinforcements of the B-pillar used in vehicles with CFRP(Carbon Fiber Reinforced Plastics) and GFRP(Glass Fiber Reinforced Plastics) from the existing steel materials. For this, it is necessary to secure structural stability that can replace the existing B-pillar while reducing the weight. Existing B-pillar are composed of steel reinforcements of various shapes, including a steel outer. Among these steel reinforcements, two steel reinforcements are to be replaced with composite materials. Each steel reinforcement is manufactured separately and bonded to the B-pillar outer by welding. However, the composite reinforcements presented in this paper are manufactured at once through compression and injection processes using patch-type CFRP and rib-structured GFRP. CFRP is attached to the high-strength part of the B-pillar to resist side loads, and the GFRP ribs are designed to resist torsion and side loads through a topology optimization technique. Through structural analysis, the designed composite B-pillar was compared with the existing B-pillar, and the weight reduction ratio was calculated.

• Composites Research
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• v.24 no.5
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• pp.34-38
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• 2011

Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90's. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.675-678
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• 2001

In this paper, an investigation was performed on the dynamic interlaminar fracture toughness of CFRP(carbon fiber reinforcement plastics). Specimens used in this experiment are CF/EPOXY laminated plates. In this experiments, Split Hopkinson s Bar test was applied to dynamic and notched flexure test. The mode II fracture toughness of each unidirectional CFRP was estimated by the analyzed deflection of the specimen and J-integral with the measured impulsive load and reactions at the supported points. As an experimental result, the vibration amplitude of 〔$0_{10}F_4/0_{10}$〕laminates appear more than that of 〔0_{10}/F_2/0_{10}$〕laminates for the J-integral and displacement velocity at a measuring point. Also, it is thought that the dynamic fracture toughness of two kind specimen with the increase of displacement velocity becomes great at a measuring point with in range of measurement.

• Steel and Composite Structures
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• v.29 no.5
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• pp.635-645
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• 2018

Beam-column joints play a significant role in static and dynamic performances of reinforced concrete frame structures. This study contributes a numerical approach of topologically optimal design of carbon fiber reinforced plastics (CFRP) to retrofit existing beam-column connections with crack patterns. In recent, CFRP is used commonly in the rehabilitation and strengthening of concrete members due to the remarkable properties, such as lightweight, anti-corrosion and simplicity to execute construction. With the target to provide an optimal CFRP configuration to effectively retrofit the beam-column connection under semi-failure situation such as given cracks, extended finite element method (X-FEM) is used by combining with multi-material topology optimization (MTO) as a mechanical description approach for strong discontinuity state to mechanically model cracked structures. The well founded mathematical formulation of topology optimization problem for cracked structures by using multiple materials is described in detail in this study. In addition, moved and regularized Heaviside functions (MRHF), that have the role of a filter in multiple materials case, is also considered. The numerical example results illustrated in two cases of beam-column joints with stationary cracks verify the validity, benefit and supremacy of the proposed method.