• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.812-819
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• 1996

This study was performed to quantify microscopically morphological characteristics of cotton fiber to identify parameters for quality evaluation using image analysis . The image of each fiber was captured by a Pc-based color imaging system using a conventional microscope. Ends of individual cotton fibers were glued on a microscope slide without any tension or straightening. A modified watershed technique was implemented to identify individual convolution segments, which were defined as sections of the fiber bordered by two neighboring convolutions. Length, area and perimeter of each convolution segment were measured directly from the image . Average width, shape factor and number of convolution segments in mm were calculated from the measured parameters. The performance of the image analysis algorithm was compared with visual varieties of cotton . The image analysis results agreed with visual inspection in 89.6% of the tested images.

• Transactions of Materials Processing
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• v.6 no.4
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• pp.346-356
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• 1997

The fiber orientation distribution and interface bonding in hot extrusion process have an effect on the maechanical properties of metal matrix composites(MMC's). Aluminium alloy matrix composites reinforced with alumina short fibers are fabricated by compocasting method. MMC's billets are extruded at high temperature through conical and curved shaped dies with various extrusion ratios and temperature. This present study was directed to describe the systematic correlation between extrusion die shape and subsequent results such as fiber breakage, fiber orientation and tensile strength to hot extruded MMC's billet. Extrusion load, tensile strength and hardness for variation of extrusion ratios and temperature are investigated to examine mechanical properties of extruded MMC's SEM fractographs of tensile specimens are observed to analyze the fracture mechanism.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.85-86
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• 2017

Fiber reinforced concrete as a construction material has been widely used. Fibers, as the reinforced component, the physical properties and the distribution influence the engineering properties of the composite. To illustrate the engineering properties, fiber distribution and orientation are necessary. Steel fibers can be easily captured by X-ray, but it is difficult them to express being numerical because they don't show as perfect circular shape on the grinding face. To get the more exact information for this, the numerical method for the orientation and distribution of fibers have to be more elaborately. This paper presents a possible method which makes the calculate for orientation possible.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.104-113
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• 1993

Characteristics of fiber-reinforced thermoplastic sheet depend on the quantity and shape of fibers. During a molding process of composites, the fiber-maxtrix separation and fober orientation are caused by the flow during the molding process. As a result, the product tends to be nonhomogeneous and anisotropic. Hence, it is very important to clarify the relations between separation-orientation and molding conditions. The correlation between the separation and the orientation have to be clarified for designing the fiber structure. In this paper, the degree of nonhomogeneity which is a measure of the separation is obtained using one-dimensional rectangular shaped part compression molding. And the orientation function is defined and measured by the image processing using soft X-rayed photograph and image scammer. Correlation between the degree of nonhomogeneity and the orientation function is discussed.

• Macromolecular Research
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• v.16 no.7
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• pp.644-650
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• 2008

This study examined the effect of nanoclays on the shape memory behavior of polyurethane (PU) in fibrous form. A cation was introduced into the PU molecules to disperse the organo-nanoclay (MMT) into poly($\varepsilon$-caprolactone) (PCL)-based PU (PCL-PU). The MMT/PCL-PU nanocomposites were then spun into fibers through melt-processing. The shape memory performance of the spun fibers was examined using a variety of thermo-mechanical tests including a new method to determine the transition temperature of shape memory polymers. The MMTs showed an improved the fixity strain rate of the MMT /PCL- PU fibers but a slight decrease in their recovery strain rate. This was explained by the limited movement of PU molecules due to the presence of nanoclays. The shape memory performance of the MMT/PCL-PU fibers was not enhanced significantly by the nanoclays. However, their recovery power was improved significantly up to a strain of approximately 50%.

• Computers and Concrete
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• v.11 no.2
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• pp.149-167
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• 2013

The complete stress-strain behavior of steel fiber reinforced concrete in compression is needed for the analysis and design of structures. An experimental investigation was carried out to generate the complete stress-strain curve of high-performance steel fiber reinforced concrete (HPSFRC) with a strength range of 52-80 MPa. The variation in concrete strength was achieved by varying the water-to-cementitious materials ratio of 0.40-0.25 and steel fiber content (Vf = 0.5, 1.0 and 1.5% with l/d = 80 and 55) in terms of fiber reinforcing parameter, at 10% silica fume replacement. The effects of these parameters on the shape of stress-strain curves are presented. Based on the test data, a simple model is proposed to generate the complete stress-strain relationship for HPSFRC. The proposed model has been found to give good correlation with the stress-strain curves generated experimentally. Inclusion of fibers into HPC improved the ductility considerably. Equations to quantify the effect of fibers on compressive strength, strain at peak stress and toughness of concrete in terms of fiber reinforcing index are also proposed, which predicted the test data quite accurately. Compressive strength prediction model was validated with the strength data of earlier researchers with an absolute variation of 2.1%.

• Textile Coloration and Finishing
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• v.23 no.3
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• pp.210-218
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• 2011

The structure of kapok fiber was characterized using FTIR and $^{13}C$-NMR spectrometers, elemental analyzer, x-ray diffractometer, SEM and IMT I-Solution ver 7.5. The kapok has a hollow tube shape and is composed of cellulose I with crystallinity of 47.95%. To develop novel oil-sorbent materials necessary to avoid the environmental pollution by spilled oil, the oil absorption capacity of various fibers such as kapok, polypropylene(PP), acryl, bamboo, cotton, rayon and wool fibers is compared in this study. The kapok fiber had the highest oil absorption capacity among the fibers and its water absorption capacity was the least. The kapok fiber selectively absorbed significant amounts of oils (43g/g of fiber for kerosene, 65g/g of fiber for soybean oil), which might be due to higher hydrophobicity of the kapok fiber, suggesting that kapok fiber may have high potential as excellent oil-absorbent materials.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.11
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• pp.1509-1517
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• 1997

Charged and uncharged particle motions and collection characteristics around a bipolar charged rectangular shape electret fiber are studied numerically. Particle inertia, fluid drag, Coulomb force and polarization force are considered to predict the particle motion around the electret fiber. The effects of particle sizes, flow velocities, number of charges and polarities are also systematically investigated. For small size particles, the single fiber collection efficiency is greatly dependent on the charge polarity and the number of charges on a particle. However, particles larger than 5.mu.m do not show charging effect on collection efficiencies in the flow velocity ranges from 1.5 cm/s to 150 cm/s when the maximum charges are within +5 to -10. The results show that a strong electric field gradient at the corner of the bipolar charged fiber plays a very important role on collecting particles regardless of its charge polarity because of the polarization force. It also shows that the most penetrating particle size for a single electret fiber decreases as the flow velocity increases and the number of charges of a particle decreases.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.4
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• pp.317-326
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• 2022

This research performed single fiber pull-out test to evaluate the effect between fineness modulus of cement composites and the fiber bond performance (bond strength and pull-out energy). A synthetic fiber (polypropylene) and a steel fiber (hooked ends type) were inserted in the middle of dog bone shape specimens which were designed with fine aggregates of F. M. 1.96, 2.69, 3.43. The experiment results showed bond strength and pullout energy of synthetic fiber are improved as fineness modulus of cement composites increases. It is considered that the frictional resistance between synthetic fiber and cement composite increases as fineness modulus of cement composite increases and consume more energy while pull out the fiber from cement composite. However bond performance of steel fiber which resist pull out by mechanical behavior is less effected on fineness modulus of cement composite. It is considered that the mechanical fixedness of hooked ends exerts a greater effect on the pullout resistance than the frictional resistance between the cement composite and the steel fiber so F. M. of fine aggregate has a relatively small effect on the pullout resistance with the steel fiber.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.72-83
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• 2022

This paper studied the effect on the microstructure, electrical properties, and compressive strength of cement mortar containing carbon fiber (CF) and steel fiber (SF), which are conductive materials. The resistivity of conductive fiber-reinforced cement mortar (FRCM) was measured using the 4-probe method, and the compressive strength was measured based on the compression test. Their performance was compared and reviewed with plain mortar (PM). Furthermore, the surface shape and composition of the fracture surface of the conductive FRCM were analyzed using a scanning electron microscope (SEM) and an energy disperse X-ray spectrometer (EDS). The results showed that the resistivity gradually increased as the curing time increased in all specimens, whereas the resistivity decreased significantly as the fiber volume fraction increased. Adding steel fibers up to 1.25% did not affect the resistivity of cement mortar considerably. On the contrast, the resistivity of carbon fiber was somewhat decreased even at low contents (ie, 0.1 to 0.3%), and thereafter, it was significantly decreased. The percolation threshold of the conductive CFRCM containing CF used in this experiment was 0.4%, and it is judged to be the optimum carbon fiber dosage to maximize the conductive effect while maintaining the compressive strength performance as much as possible. For the surface shape and composition analysis of conductive FRCM, the fracture surface was observed through SEM-EDS. These results are considered to be very useful in establishing the microstructure mechanism of reinforcing fibers in cement mortars.