Han-Yong Jeon

Dimensional stability of cotton-spandex interlock structures under relaxation

In this study, dimensional characteristics of core spun cotton/spandex interlock structures with high, medium and low tightness factors were studied under dry-, wet-, and full relaxation conditions. Results are compared with those for similar fabrics knitted from 100 % cotton. Dimensional characteristics of samples of core-spun cotton/spandex and cotton are measured by considering the changing of course-, wale- densities and stitch densities under dry, wet and full relaxation conditions. Based on these data, dimensional constants (U-values) were predicted under 95 % significance level. Higher U-values are reported with cotton/spandex interlocks than 100 % cotton and under full relaxation, cotton/spandex shows the U-values with lesser CV%. Stitch density growth is linearly correlated with tightness factor for both interlock material structures. Excellent resiliency property of cotton/spandex yarns increases tightness factors at machine off state and during relaxation states. Cotton/spandex interlock structures show more prominent co-relationship with their tightness factors on their dimensional parameters.

Evaluation of pullout and drainage properties of geosynthetic reinforcements in weathered granite backfill soils

The main aim of this research is to systematize the reinforced-earth wall system using the geosynthetic reinforcements in the weathered granite backfill soils containing relatively large amount of fines with low permeability. As a staged endeavor to accomplish this purpose, laboratory pullout tests and finite element modeling are carried out focusing on the analysis of friction characteristics associated with interaction behaviors of the geosynthetic reinforcements composed of geogrid with outstanding tensile resistance and geotextile with a sufficient drainage properties. In addition, drainage effects of the geotextile laid below the geogrid are examined based on the analysis of finite difference numerical modeling. From the present investigation, it is concluded that the geosynthetic reinforcements in the weathered granite backfills can be used to achieve combined effects of the reduction of deformations and the increase of tensile resistance, together with drainage effects.

Performance Evaluation of Isotropic Spunbonded Geotextiles for Vacuum Consolidation

In this study, the performance of isotropic spun-bonded geotextiles, which are used in vacuum consolidation,was tested both in the laboratory and in the field. Two kinds of isotropic spun-bonded geotextiles were prepared. One was a matrix/binder structure using low-melting polyethylene terephthalate (PET) copolymer (co-PET) fibers forweb bonding. The other consisted of sheath/core (co-PET/PET) fibers. Through the index test, it was seen that the performanceof the sheath/core structure isotropic spun-bonded geotextiles was better for use with vacuum consolidationthan the matrix/binder structure isotropic spun-bonded geotextiles. However, the drainage performance test, which simulatesa construction environment, showed that the sheath/core structure isotropic spun-bonded geotextiles were unstable. The matrix/binder isotropic spun-bonded geotextiles showed better results for the drainage test and the field testresults for the matrix/binder isotropic spun-bonded geotextiles showed that they were suitable for use with vacuum consolidation.

Evaluation of Engineering Performance of Wet-Laid Nonwoven Fabrics Using Three-Component Fiber Blending

c2016 The Korean Fiber Society Abstract: In this study, polyarylate nonwoven fabrics were manufactured by a wet-laid process by using viscose rayon and amorphous PET fiber as binding fibers. The engineering performance was evaluated after calendering to obtain a compact structure. From the polyarylate wet-laid nonwoven fabrics, it was confirmed that polyarylate fiber and binding fibers were mixed evenly. Through calendering, the permeability and pore size of the wetlaid nonwoven fabrics were significantly reduced owing to the compact structure. The bending strength and tensile strength increased through calendering, but the tensile elongation decreased. From an analysis of the tensile properties, monolayer wet-laid nonwoven fabrics showed better evenness than multilayer wet-laid nonwoven fabrics. In addition, multilayer wet-laid nonwoven fabrics showed a higher anisotropy than monolayer wet-laid nonwoven fabrics.

Study of Properties for Compatibility and Composition of PLA/PMMA/PBAT Blends

필요하다[1−7]. 예를 들어 PVA, PMMA, PC는 PLA와 높은 상용성을 보여 블렌딩 시 첨가제가 필요하지 않으나[1,2,4] PP, PBAT는 비 상용성이므로 첨가제가 필요하다[6−9]. 그 중 PMMA(poly methyl methacrylate)는 PLA와 상용 성이 높은 범용 고분자 중 하나이고[10−13], PBAT(poly butylene adipate-co-terephthalate)는 생분해성 고분자이며 높은 충격강도와 연신율을 가지고 있어 PLA/PMMA, PLA/ PBAT 블렌딩 연구가 많이 진행되고 있다. 하지만 PBAT는 PLA와 비상용성을 갖기 때문에 상용화제 첨가와 같은 방 법이 필요하다[8,9]. 기존 연구에서는 PLA/PBAT 블렌드의 상용화제로 PLA-g-MA가 많이 사용되어 왔다[8]. 상용화

Prediction and Interpretation of Hydraulic Permeability for Nonwoven Fabrics Considering Hypothetical 2-D Layer

The permeability defined by Darcy’s law indicates the degree of ability that a fluid can flow through nonwoven media under a differential pressure in laminar flow. The permeability generally indicates the specific permeability or absolute permeability. On the other hand, if the fluid is water, the permeability indicates the hydraulic conductivity or permeability coefficient. The permeability is one of the important properties for nonwoven media and a prediction of the permeability acts as a bridge between the manufacturing technology and performance requirements. Because capillary channel theory aims to make the flow of fluid easier and more understandable, many models are based on capillary channel theory. On the other hand, the theory has a limitation in that it is unsuitable for high porosity media. In this study, a very thin downstream layer, which was suggested by Lifshutz [9], was introduced to derive a prediction model of hydraulic permeability. Needle-punched and spunbonded nonwoven fabrics with various basis weights were used in the cross-plain water permeability test. From this ‘thin layer’ model, reasonable agreement between the predicted and experimental results was obtained.

Resistance Evaluation of Geomembrane for Water Barrier Application by Puncture Strength

This study focused on the protection effect of geosynthetics installed on geomembrane to resist against puncture load. For this, a puncture unit was used and model test was conducted with various types of puncture load created by different shapes of the puncture tools. The puncture resistance of the installed geosynthetics as protective material for the geomembrane was_varied depending on the types of the geosynthetics and the puncture load. When a single cone shape of puncture tool was used, the protection effect of single cone used on all kinds of geosynthetics is lower than those of other puncture tools. Finally, geocomposite showed the best protection effect against the all puncture tools.

Analysis of Environmental Condition Effects of Waste Landfill on Geomembrane Performance

The effects of acidic and alkaline solutions to be considered waste on the chemical resistance of high density polyethylene (HDPE) geomembranes (GMs) were evaluated. Damaged and intact smooth/textured specimens were immersed in acidic, alkaline and distilled water (pH=4, 12, 8 and 7), and incubated at 20, 40, 60 and 80 °C respectively. Tensile stress of specimens was periodically determined by constant rate of load tensile testing apparatus while polymer structure was examined by a scanning electro-microscope. Damaged HDPE GMs showed excellent acidity-resistance as intact HDPE GMs. High temperature imparted flexibility in HDPE GMs which in turn showed lower tensile strength.