• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.813-821
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• 2002

Glass fiber reinforced PET matrix composite was manufactured by rapid press consolidation technique as functions of temperature, pressure and time in pre-heating, consolidation and solidification stages. The optimal manufacturing conditions for this composite were discussed based on the void content, tensile, interlaminar shear and impact properties. In addition, the levels of crystallinity with various manufacturing conditions were measured using differential scanning calorimetry to investigate the mechanical properties of this composite material as a function of crystallinity. Among many processing parameters, the mold temperature and the cooling rate after forming were found to be the most critical factors in determining the level of crystallinity and mechanical properties. The level of crystallinity affects the tensile properties to some degree. However, impact properties are affected much more. It also affects the degree of ductility, which determines the impact energy of this material.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.1
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• pp.45-49
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• 2003

Tensile strength of the woven glass fiber reinforced PET (Poly-Ethylene-Terephthalate) matrix composite manufactured by rapid press consolidation technique was investigated and evaluated. During pre-heating, consolidation and solidification stages, the optimal manufacturing conditions for this composite were discussed based on the void content and tensile properties depending on vacuum condition. It is found that the effect of vacuum condition during preheating gives a substantial difference on the strength as well as microstructure. It is also found that the failure micromechanism shows several energy absorption processes enhancing fracture toughness.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.248-256
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• 2017

Groundwater drawdown was pointed out as one of the causes of induced settlement on high speed railways, especially concrete track. In this study, the effect of groundwater variation on settlement was evaluated through a comparison of field measurements with numerical analysis results. A trial and error method, i.e., repeated numerical analyses by changing material properties, was used to calibrate the model. The model was applied to investigate the effect of groundwater drawdown, thickness of soft layer, and embankment height on residual settlement after concrete track completion. A soft layer thicker than 4m would result in more than 30mm of settlement; a detailed analysis of groundwater behavior thus should be conducted from the design stage to construction.