• Korean Journal of Materials Research
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• v.23 no.7
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• pp.366-372
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• 2013

Flexible polyurethane/clay porous nanocomposite foams were synthesized using natural and organically modified montmorillonite clays such as bentonite, closite 10A and closite 30B. The content of nanoclays was varied from 1 to 5 wt% of polyol. Dispersion of clay in Polyurethane(PU) matrix was investigated by X-ray diffraction(Cu-$K{\alpha}$ rays of wavelength $1.54{\AA}$) using an X-ray diffractometer. Also, we determined that the thermal resistance of PU foam increased with added clay, compared to that of pure PU foam. The cell size and the fraction of open cells of the precursor foam were controlled by the addition of clay to the polyurethane foam. Modified clays were found to be more efficient cell openers than the unmodified clay. In addition, the tensile strength and elongation of the polyurethane/clay porous nanocomposites were examined. Increasing clay content increased the mechanical properties of the composites, such as tensile strength, and elongation at break. However, increasing the content over 5 wt% deteriorated the properties of the composites. We found that the nanofillers(bentonite, closite 10A and closite 30B) improved the thermal stability of the nanocomposite foam. The nanocomposite foam containing 3 wt% of closite 30B exhibited the best tensile strength and thermal stability.

• Journal of Soil and Groundwater Environment
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• v.7 no.1
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• pp.41-51
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• 2002

Recently, domestic waste landfills are constructed sometimes on seashore area to provide large landfill area. In order to strengthen the foundation of landfills and to prevent the infiltration of leachate through the bottom, many cases of constructing cement hardened liners on seashore clays are found. In these cases, it is possible to have cracks in the hardened liners due to settlement with waste load since the stiffness of the hardened liner Is greater than that of clay liners. In this study, the capability of Self-Sealing and Self-Healing (SSSH) liner made with a seashore clay in the metropolitan landfill to prevent the percolation of water and leachate is examined using flexible-wall permeameter test and using uniaxial compression test. Applicability of SSSH to weathered granitic soil is also examined for self-sealing capabilities. The result of Flexible permeameter test for SSSH with the seashore clay showed that permeability obtained was lower than permeability criteria of Korean waste management law. The permeability and strength characteristics of SSSH with granitic soil and bentonite showed better results than with the seashore clay.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.3
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• pp.31-41
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• 2019

More than 90% of roadway in the world are paved as asphalt concrete pavement due to its excellent properties compared with other paving materials; excellent riding quality, flexibility, anti-icing property and easy maintenance-ability. In this study, to make best use of the softer property of the asphalt mixture, the flexible sand asphalt mixture (FSAM) was developed for pedestrian ways. The mix design was conducted to prepare FSAM using PG64-22 asphalt, screenings (sand) less than 5mm, crumb rubber, hydrated lime and limestone powder without coarse aggregate. The deformation strength ($S_D$), indirect tensile strength (ITS) and tensile strength ratio (TSR) tests were conducted to make sure durability of FSAM performance. The impact energy absorption and flexibility were measured by drop-boll test and the resilient modulus ($M_R$) test. The impact energy absorption of FSAM was compared with normal asphalt pavement, concrete pavement, stone and concrete block for pedestrian way. As a result of drop-boll test, FSAM showed higher impact energy absorption compared with other paving materials with the range of 18% to 43%. Impact energy absorption of FSAM increased with increasing test temperature from 5 to $40^{\circ}C$. The results of $M_R$ test at $5^{\circ}C$ showed that the flexibility of FSPA was increased further, because the $M_R$ value of the sand asphalt was measured to be 38% lower than normal dense-graded asphalt mixture (WC-1). Therefore, it was concluded that the FSAM could provide a high impact absorbing characteristics, which would improve walking quality of the pedestrian ways.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.67-67
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• 2012

Graphene, two-dimensional one-atom-thick planar sheet of carbon atoms densely packed in a honeycomb crystal lattice, exhibits fascinating electrical properties, such as a linear energy dispersion relation and high mobility in addition to a wide-range optical absorption and high thermal conductivity. Graphene's outstanding tensile strength allows graphene-based electronic and photonic devices to be flexible, bendable, or even stretchable. Recently many groups have reported high performance electronic and optoelectronic devices based on graphene materials, i.e. field-effect transistors, gas sensors, nonvolatile memory devices, and plasmonic waveguides, in which versatile properties of graphene materials have been incorporated into a flexible electronic or optoelectronic platform. However, there are several fundamental or technological hurdles to be overcome in real applications of graphene in electronics and optoelectronics. In this tutorial we will present a short introduction to the basic material properties and recent progresses in applications of graphene to electronics and optoelectronics and discuss future outlook of graphene-based devices.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.3
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• pp.250-258
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• 2018

Free Standing Hybrid Riser (FSHR) is comprised of vertical steel risers and Flexible Jumpers (FJ). They are jointly connected to a submerged Buoyancy Can (BC). There are several factors that have influence on the behavior of FSHR such as the span distance between an offshore platform and a foundation, BC up-lift force, BC submerged location and FJ length. An optimization method through a parametric study is presented. Firstly, descriptions for the overall arrangement and characteristics of FSHR are introduced. Secondly, a flowchart for optimization of FSHR is suggested. Following that, it is described how to select reasonable ranges for a parametric study and determine each of optimal configuration options. Lastly, numerical analysis based on this procedure is performed through a case study. In conclusion, the relation among those parameters is analyzed and non-dimensional parametric ranges on optimal arrangements are suggested. Additionally, strength analysis is performed with variation in the configuration.

• Journal of Energy Engineering
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• v.24 no.3
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• pp.128-134
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• 2015

This research is that analyze multi-body system that have flexible and rigid body. Transfer robots are widely used mainly in automobile industry owing to its capability to handle heavy parts with high speed in wide range of movement. For the transfer robots to widen the application area, a new three-axis mechanism with heavy payload has been recently developed in consideration of the strength and stiffness. For the purpose, transient dynamic analysis is carried out to find the component position yielding a certain time. Though this research, we can analysis stress distribution and deformation of robot component.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.32-39
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• 2015

With the simplicity of process and high reliability in chip or package bonding, epoxy solder paste (ESP) has been recently considered as a competitive bonding material. The ESP material is composed of solder powder and epoxy formulation which can remove oxide layers on the surface of solder powder and pad finish metal. The bonding formed using ESP shows outstanding bonding strength and suppresses electrical short between adjacent pads or leads owing to the reinforced structure by cured epoxy after the bonding. ESP is also expected to suppress the formation and growth of whisker on the pads or leads. With the mentioned advantages, ESP is anticipated to become a spotlighted bonding material in the assembly of flexible electronics and electronic modules in automotive vehicles.

• Advanced Composite Materials
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• v.18 no.1
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• pp.77-93
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• 2009

This paper investigated the damage transition mechanism between the fiber-breaking mode and the fiber-avoiding crack mode when the fiber-length is reduced in the unidirectional discontinuous carbon fiber-reinforced-plastics (CFRP) composites. The critical fiber-length for the transition is a key parameter for the manufacturing of flexible and high-strength CFRP composites with thermoset resin, because below this limit, we cannot take full advantage of the superior strength properties of fibers. For this discussion, we presented a numerical model for the microscopic damage and fracture of unidirectional discontinuous fiber-reinforced plastics. The model addressed the microscopic damage generated in these composites; the matrix crack with continuum damage mechanics model and the fiber breakage with the Weibull model for fiber strengths. With this numerical model, the damage transition behavior was discussed when the fiber length was varied. The comparison revealed that the length of discontinuous fibers in composites influences the formation and growth of the cluster of fiber-end damage, which causes the damage mode transition. Since the composite strength is significantly reduced below the critical fiber-length for the transition to fiber-avoiding crack mode, we should understand the damage mode transition appropriately with the analysis on the cluster growth of fiber-end damage.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.1
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• pp.46-51
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• 1999

The most important effect of refining is believed as the internal fibrillation. The internal fibrillation is the separation of the fiber wall into several lamellae. The internal fibrillation results in fiber swelling as water penetrates the fiber wall. The increase in paper strength as a result of refining was due to delamination which made the fiber more flexible. Pulp fibers are refined to 20, 40, and 70$^{\circ}$SR freeness at Valley beater. Changes of Physical paper properties are analyzed depending on fiber wall thickness and fiber's collapse index at 2.5 and 5.6kg$_f$ refining load. At same $^[\circ}$SR freeness with 2.5kg$_f$ refining load, fiber wall thickness is increased further than at high 5.6kg$_f$ refining load. With higher fiber wall thickness by lower intensity refining load, higher internal fibrillation, flexibility, collapsability of fibers are achieved. Those effects improve WRV, tensile strength, and burst strength. Tear strength shows opposite trend to tensile and burst strength as usual.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.3
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• pp.35-44
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• 1985

This research explored the effects of abrasion, laundering, and abrasion/laundering interaction upon wear of 15 durable nonwoven fabrics. Wear was measured in terms of changes in tensile strength and stiffness. The test materials consisted of nine different dry-laid commercial interfacing fabrics of various fiber contents and six spunbonded poyester and polypropylene fabrics. Three fixed levels of abrasion and four fixed levels of laundering made up the 3$\times$4 factorial analysis used for the experiment and the analysis of variance. Findings revealed that abrasion had a greater effect than laundering on strength and stiffness of the tested fabrics. Laundering seemed related to the particular fibers used and to the fixation quality of fiber bonds. Spunbonded webs performed better than dry-laid webs in retaining tensile strength Stiffness change occurred more readily than strength change. Lighter, flexible, stretchable fabrics seemed less easily abraded than heavier, stiff, less stretchable fabrics. The interfacing fabrics of 70/20/$10\%$ nylon/polyester/rayon blends with high crosswise stretchability effectively resisted wear caused by abrasion and laundering. Further research is recommended to study the effects of longer abrasion periods and additional laundering cycles o,1 wear qualities of nonwoven fabrics. Additional factors such as amount and fixation methods of bonding agents, the effect of shear distortion, seam construction, and drycleaning solvents could also be studied.