• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.336-341
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• 1998

Steel fiber reinforced concrete(SFRC) is a composite material possessing many physical and mechanical properties which are distinct from unreinforced concrete. The use of steel fiber reinforcement to improve the flexural and tensile strengths, extensibility and toughness of ordinary cement concrete is well known at present, but reinforcement of polymer concrete with steel fibers has been hardly reported untill now. The objective of this study was to improve the properties of the polymer concrete by addition of steel fibers. In this paper steel fiber reinforced polymer concrete is prepared with various steel fiber contents and aspect ratio($\ell$ /d), and their mechanical properties were investigated experimentally.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.154-159
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• 1999

In this paper we present tile results of an experimental investigation on the physical and mechanical properties of carbon fiber grid, polymer mortar, and carbon fiber grid reinforced plain concrete flexural members. In order to repairing and reinforcing damaged and/or deteriorated existing concrete structural members, new materials have been developed and utilized in the construction industries. But the physical and mechanical behaviors of the material are not well understood. To use the material effectively various aspects of the material must be throughly investigated analytically as well as experimentally. In this investigation we found the physical and mechanical properties of carbon fiber grid and polymer mortar which are directly utilized in the repair and reinforcement design of damaged or deteriorated concrete structures. In addition, we also investigate the strengthening effect of carbon fiber grid on the plain concrete flexural test specimens. It was found that the material can be used to repair and strengthen the concrete structures effectively.

• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.4
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• pp.73-81
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the compaction and compressive strength properties of stress-strain, elastic modulus and fracture mode CSG materials reinforced polypropylene fiber. Polypropylene fiber widely used for concrete reinforcement is randomly distributed into cemented sand. The two types of polypropylene fiber (monofillament and fibrillated fiber) were used and fiber fraction ratio was 0, 0.2 %, 0.4 %, 0.6 % and 0.8 % by the weight of total dry soil. The effect of fiber fraction ratio and fiber shape on compaction and compressive strength were investigated. The optimum moisture contents (OMC) of CSG material increased as fiber fraction increased and the dry density of CSG material decreased as fiber fraction. Also, the maximum increase in compressive strength was obtained at 0.4 % content of monofillament and fibrillated fiber. CSG material behaviour was controlled not only by fiber fraction but also fiber distribution, fiber shape and fiber type.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.3
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• pp.90-95
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• 2000

Today fiber composite materials are routinely used in such wide applications as ships automobiles aircraft space vehi-cles containers sporting goods and appliances. The current knowledge of machining glass fiber reinforced polyester com-posites unfortunately is inadequate for its optimum utilization in many applications. Therefore This paper deals with drilling characteristic of glass fiber reinforced polyester composites. In the drilling of glass fiber reinforced polyester the quality of the cut surfaces is strongly dependent on the drilling parameters. drilling tests were carried out on glass fiber reinforced polyester using standard HSS tools. The material containing random chopped strand fibers and woven roving was fabricated by hand lay-up The entrance and exit surface of the holes was examined. The cutting force was also mea-sured to analyze the drilling characteristics,.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.651-658
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• 2002

A series of experimental study are performed to evaluate the shear strength and friction properties of fiber-mixed soil as backfill material in reinforced earth wall. In order to evaluate the properties of shear strength the big-size direct shear tests are carried out and on the friction properties, the shear friction tests and the pull-out tests are performed. In the results, when the mixed ratio of the net type fiber is 0.2%, the reinforcement effect was better than the others. Also the reinforcement effect of the net type fiber was larger than that of the line type fiber.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.6
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• pp.799-804
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• 2011

CFRP(Carbon Fiber Reinforced Plastics) has been used many industries aerospace, automobile, medical device and building material industries, etc. Because it is lighter than other metals and has good properties, such as rigidity, strength and wear. CFRP may be cured integrity. However, it needs postprocessing similar to drilling or endmilling for shape cutting and combination of various material. In this paper, tool dynamometer and accelerometer used to signal analysis for machining properties under various cutting conditions and tool shape changes. In addition, microscope used to verify the machined CFRP surface. As the results, it was found that the cutting force and the vibration were decreased in the increasing of cutting edge (2-flute < 4-flute < composite tool), and the good machined surface can be obtained in this experiments.

• Korean Journal of Materials Research
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• v.20 no.3
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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.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.908-912
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• 1996

FRMLs consist of thin sheets of high strength metal, which are laminated using a structural adhesive and high strength fibers. ARALL(Aramid-fiber Reinforced Aluminum alloy Laminates) of FRMLs is a new class of hybrid material. HERALL(Heracron Reinforced Aluminum Laminate) i.e. domestic ARALL is made of homemade aramid fibers, adhesives and adhesive technique. Domestic aramid fiber is Heracron manufactured by KOLON and domestic adhesive is epoxy resin manufactured by Han Kuk Fiber. In this study, Fatigue crack propagation behavior was examined in a 2024-T3 aluminum alloy/aramid-fiber epoxy 3/2 laminated composites, HERALL and ARAL $L^{ⓡ}$-2 LAMINATE comparing with 2024-T3 aluminum alloy. The extrinsic toughening mechanisms in HERALL and ARALL were examined, the crack bridging behavior of fibers was analyzed by new algorithm, which measures crack bridging stress, and the crack bridging zone length was measured.

• Journal of the Korean Wood Science and Technology
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• v.43 no.5
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• pp.652-660
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• 2015

To study the bearing characteristics of glass fiber reinforced glulam for structural design, bearing strength tests were performed. Bearing loads were applied in the direction parallel to the grains, and the holes were prepared in such a way that the bolts would bear and support all the layers. The yield bearing strengths of the glass fiber reinforced glulam were found to be similar to those of the non-reinforced glulam, and were almost constant regardless of increases in bolt diameter. The ratio of the experimental yield bearing strength to the estimated bearing strength according to the suggested equation of the Korea Building Code and National Design Specification was 0.91~1.03. For the non-reinforced glulam and the sheet glass fiber reinforced plastic glulam, the maximum bearing load was measured according to the splitting fracture of specimens under bolt. The textile glass fiber reinforced glulam underwent only an embedding failure caused by the bearing load. The failure mode of reinforced glulam according to bearing load will influence the failure behavior of bolted connection, and estimating the shear yield strength of the bolted connection of the reinforced glulam is necessary, not only by using the bearing strength characteristics but also using the fracture toughness of the reinforced glulam.

• Computers and Concrete
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• v.18 no.5
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• pp.999-1018
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• 2016

Enhanced tensile properties of fiber reinforced concrete make it suitable for strengthening of reinforced concrete elements due to their superior corrosion resistance and high tensile strength properties. Recently, the use of fibers as strengthening material has increased motivating the development of numerical tools for the design of this type of intervention technique. This paper presents numerical analysis results carried out on a set of concrete beams reinforced with short fibers. To this purpose, a database of experimental results was collected from an available literature. A reliable and simple three-dimensional Finite Element (FE) model was defined. The linear and nonlinear behavior of all materials was adequately modeled by employing appropriate constitutive laws in the numerical simulations. To simulate the fiber reinforced concrete cracking tensile behavior an approach grounded on the solid basis of micromechanics was used. The results reveal that the developed models can accurately capture the performance and predict the load-carrying capacity of such reinforced concrete members. Furthermore, a parametric study is conducted using the validated models to investigate the effect of fiber material type, fiber volume fraction, and concrete compressive strength on the performance of concrete beams.