• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1546-1553
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• 2005

In this study, geotextiles was applied on the selected track-bed, which is relatively economical and efficient way to prevent the problem of mud-pumping and settlement. Field testing sections from Mock-haeng to Dong-ryang in the Chung-buk lines in Korea were selected to investigate the state of track and roadbed. And three places were chosen among 1,700 spots where mud-pumping was frequently occurred and maintenance required. At the curved section with radius of 500m between Mock-haeng and Dong-ryang, we divided this testing site into 5 section and 4 different types of geotextile were installed and left the last section with no reinforcement. Total length of the test site was 200m and individual length of each site was 40 m. In order to understand the state and the strength of prepared roadbed, stiffness and physical properties of the roadbed soil were evaluated and analyzed. Also, after the installation, mud-pumping, settlement of elastic or plastic sleeper, failure of track, wheel-loads, lateral force and earth pressures were investigated.

• Composites Research
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• v.29 no.6
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• pp.363-368
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• 2016

This study performed a nonlinear finite element crash analysis of guardrail structures using supports made of composite materials. In this study, we used a new [0/90/90/0] laminated Boron fiber composite for resisting the crash effects. Based on the improved ground-structure interaction model, appropriate ground properties to the support were determined. In particular, the complex crash mechanism of guardrails was studied using various parameters. The parametric studies are focused on the various effects of car crash on the structural performance and thickness of supports. The numerical results for various parameters are verified by comparing those using existing steel materials.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.734-743
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• 2005

In this study, geotextiles was applied on the selected track-bed, which is relatively economical and efficient way to prevent the problem of mud-pumping and settlement. Field testing sections from Mock-haeng to Dong-ryang in the Chung-La lines in Korea were selected to investigate the state of track and roadbed. And three places were chosen among 1,700 spots where mud-pumping was frequently occurred and maintenance required. At the curved section with radius of 500m between Mock-haeng and Dong-ryang, we divided this testing site into 5 section and 4 different types of geotextile were installed and left the last section with no reinforcement. Total length of the test site was 200m and individual length of each site was 40 m. In order to understand the state and the strength of prepared roadbed, stiffness and physical properties of the roadbed soil were evaluated and analyzed. Also, after the installation, mud-pumping, settlement of elastic or plastic sleeper, failure of track, wheel-loads, lateral force and earth pressures were investigated.

• Journal of Power System Engineering
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• v.19 no.4
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• pp.17-23
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• 2015

Because of the energy resources shortage and global pollution, the wind power systems have been developed consistently. Among the components of the wind power system, the rotor blades are the most important component. Generally it is made of GFRP material. Recently, GFRP material has been replaced by CFRP composite material in the blade which has an aerodynamic profile and twisted tip. However the failures has occurred in the trailing edge of the blade by the severe wind loading. Thus, tougher material than CFRP material is needed as like the aramid fiber. In this study, we investigated the mechanical behaviors of the blade using aramid fiber composites about wind speed variation. One-way FSI (fluid-structure interaction)analysis for the wind rotor blade was conducted. The structural analyses using the surface pressure loading resulted from wind flow field analysis were carried out. The results and analysis procedure in this paper can be utilized for the best strength design of the blade with aramid fiber composites.

• International Journal of Highway Engineering
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• v.14 no.5
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• pp.21-29
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• 2012

PURPOSES: This study is to investigate the mechanical performance of the fiber reinforced lean concrete with respect to different types of fibers. METHODS: Increased vehicle weight and other causes from the exposed conditions have accelerated the deteriorations of road pavement. A new multi-functional composite pavement system is being developed recently in order to extend service life and upgrade the pavement. A variety of tests were conducted before and after hardening of the concrete. RESULTS: From the test results, it was found that the use of different types of fibers did not affect the compressive strength development. This might be due to the inherent property of the lean concrete. When steel fibers were used relatively greater flexural strength and flexural fracture toughness were developed. Also addition of fly ash by replacing a part of Portland cement the fracture toughness was slightly increased. CONCLUSIONS: It has been known that the addition of fibers and use of mineral admixture can be positively considered in the development of multi-functional composite pavement system as its required mechanical performance is obtained.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2007.11a
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• pp.93-102
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• 2007

Biocomposite was organized with biodegradable polymer and natural fiber that has potential to be used as replacement for glass fiber reinforced polymer composite with the benefits of low cost, low density, acceptable specific strength, biodegradability, etc. Until now, non-wood fibers have been used as reinforcements of biocomposite which are all plant-based fibers. The present study focused on investigating the fabrication and characterization of biocomposite reinforced with red algae fiber. The bleached red algae fiber(BRAF) showed very similar crystallinity to the cellulose. It has high stability against thermal degradation (maximum thermal decomposition temperature of 359.3$^{\circ}C$) and thermal expansion. Biocomposites reinforced with BRAF have been fabricated by a compression molding method and their mechanical and thermal properties have been studied. The storage modulus and the thermomechanical stability of PBS matrix are markedly improved with reinforcing the BRAF. These results support that the red algae fiber can be used as an excellent reinforcement of biocomposites as "green-composite" or "eco-composite".

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.9
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• pp.2782-2791
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• 1996

The effective longitudinal shear modulus(LSM) of continuous composites is studied theoretically and numerically using 3-phase unit cell model. Circular, hexagonal and rectangular shapes of reinforced fiber are considered to predict the shear modulus as a function of elastic modulus of each phase and volume fraction of interphase and reinforced fiber. It is found that rectangular fiber shape in low fiber volume fraction($v_f$<30%) and circular fiber shape in high volume fraction($v_f$>40%) shows the higher longitudinal shear modulus. Also the obtained values of LSM for rectangular array and by numerical analysis are higher than those of hexagonal array and by theoretical analysis respectively. The reinforcing effects of interphase are more significant in cases of higher fiber volume fraction and circular fiber shape. Not only the spatial distribution and shape of reinforcing fiber but also the volume of interphase have a pronounced effects on the overall LSM. It is also found that the tangent moduous of 2-and 3-phase polymer matrix composites is insensitive to the shape and distribution of reinforcing fibers.

• Composites Research
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• v.30 no.6
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• pp.399-405
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• 2017

We manufactured the long fiber-reinforced thermoplastic prototype of under cover using in-line compounding technology, and investigated the formability, mechanical properties and durability of the prototype of under cover. We manufactured the injection mold for the prototype through injection molding analysis and consideration of weight reduction. We investigated the formability of the prototype by evaluating the residual length and dispersion of fiber, and also tested the mechanical properties such as flexural strength, stiffness and impact strength. We investigated the durability of the prototype by the Key-Life Test(KLT) method which is generally used for the automotive interior parts.

• Journal of Korean Association for Spatial Structures
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• v.15 no.2
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• pp.69-77
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• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) has a outstanding tensile hardening behaviour after a crack develops, which gives ductility to structures. Existing shear strength model for fiber reinforced concrete is entirely based on crack opening behavior(mode I) which comes from flexural-shear failure, not considering shear-slip behavior(mode II). To find out the mode I and mode II behavior on a crack in UHPFRC simultaneously, maximum shear strength of cracked UHPFRC is investigated from twenty-four push-off test results. The shear stress on a crack is derived as variable of initial crack width and fiber volume ratio. Test results show that shear slippage is proportional to crack opening, which leads to relationship between shear transfer strength and crack width. Based on the test results a hypothesis is proposed for the physical mechanics of shear transfer in UHPFRC by tensile hardening behavior in stead of aggregate interlocking in reinforced concrete. Shear transfer strength based on tensile hardening behavior in UHPFRC is suggested and this suggestion was verified by comparing direct tensile test results and push-off test results.

• Journal of the Society of Disaster Information
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• v.10 no.3
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• pp.388-395
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• 2014

In this paper, usability and use force on the structure and does not have a big impact on the development of existing materials developed using materials to their full impact/blast resistant Complex configuration on the panel that can be implemented. Each material of the characteristics so that they can exert in layers of layer formed panels in layers. Structure of the general structure is to keep strength and endurance, maintenance and minimize the damage can be utilized for knee brace to do basic research, for creating the panel.