• Fibers and Polymers
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• v.2 no.1
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• pp.144-147
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• 2001

The HVI properites and Mantis single fiber tensile properties were analyzed to evaluate the relationship between fiber and bundle tensile properties. For this study, a new method has been developed for estimating the modulus and toughness of cotton fiber bundles directly from the HVI tenacity-elongation curves. The single fiber tensile properties were shown to be translated well into the bundle tensile properties. The single fiber breaking elongation was found to be the most significant contributing factor to bundle tensile properties. The bundle breaking elongation and toughness were shown to increase as the single fiber breaking elongation increased. The bundle modulus increased as the single fiber breaking elongation and/or standard deviation of single fiber breaking elongation decreased.

• Journal of Mechanical Science and Technology
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• v.15 no.7
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• pp.823-830
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• 2001

The single fiber pull-out technique has been commonly used to characterize the mechanical behavior of fiber/matrix interface in fiber reinforced composite materials. In this study, an improved analysis considering the effect of thermal residual stresses in both radial and axial directions is developed for the single fiber pull-out test. It is found to have the pronounced effects on the stress transfer properties across the interface and the interfacial debonding behavior.

• Journal of Ocean Engineering and Technology
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• v.12 no.3 s.29
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• pp.31-41
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• 1998

Single fiber fragmentation technique was used to evaluate the change of interfacial properties by degradation of fiber tensile strength in the fiber reinforced composites. The influences of fiber tensile strength on the interfacial properties have been evaluated by the fragmentation specimens(weak fiber samples) of glass fiber/epoxy resin that was made using the pre-degraded glass fiber in distilled water at $80^{circ}C$ for specified periods. The effects of the immersion time on the interfacial properties in the distilled water at $80^{circ}C$ also have been evaluated by the fragmentation specimens(original fiber samples) of glass fiber/epoxy resin that was made using the received glass fiber. As the result, the tensile strength of glass fiber was decreased with the increasing of the treatment time in the distilled water at $80^{circ}C$ and the interfacial shear strength was independent of the change of the glass fiber strength in the single fiber fragmentation test. But in the durability test using the single fiber fragmentation specimen, interfacial shear strength decreased with the increasing of the immersion time in distilled water ar $80^{circ}C$. And it turned out that the evaluating of interfacial shear strength using original fiber tensile strength was valuable in the durability test for the water environment by the single fiber fragmentation technique.

• International Journal of Aeronautical and Space Sciences
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• v.9 no.2
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• pp.18-33
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• 2008

This paper presents design optimization of a new Active Twist Rotor (ATR) blade and conducts its aeroelastic analysis in forward flight condition. In order to improve a twist actuation performance, the present ATR blade utilizes a single crystal piezoelectric fiber composite actuator and the blade cross-sectional layout is designed through an optimization procedure. The single crystal piezoelectric fiber composite actuator has excellent piezoelectric strain performance when compared with the previous piezoelectric fiber composites such as Active Fiber Composites (AFC) and Macro Fiber Composites (MFC). Further design optimization gives a cross-sectional layout that maximizes the static twist actuation while satisfying various blade design requirements. After the design optimization is completed successfully, an aeroelastic analysis of the present ATR blade in forward flight is conducted to confirm the efficiency in reducing the vibratory loads at both fixed- and rotating-systems. Numerical simulation shows that the present ATR blade utilizing single crystal piezoelectric fiber composites may reduce the vibratory loads significantly even with much lower input-voltage when compared with that used in the previous ATR blade. However, for an application of the present single crystal piezoelectric actuator to a full scaled rotor blade, several issues exist. Difficulty of manufacturing in a large size and severe brittleness in its material characteristics will need to be examined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1384-1392
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• 2002

Single fiber pull-out technique has been commonly used to characterize the mechanical behavior of interface in fiber reinforced composite materials. An improved analysis considering the effects of transversely isotropic properties of fiber and the effects of thermal residual stresses in both radial and axial directions along the fiber/matrix interface is developed for the single fiber pull-out test. Although the stress transfer properties across the interface is not much affected by considering the transversely isotropic properties of fiber, interfacial debonding is notably encouraged by the effect. The interfacial shear stress that plays an important role in interfacial debonding is very much affected by the component of axial thermal residual stress in the bonded region, which can induce a two-way debonding mechanism.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.663-664
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• 2006

In the electronic, medical, aerospace and automobile industries, many products and parts are manufactured by joining. Recently, as these get smaller, micro joining is becoming more and more important. In this study, micro wire-to-micro wire parallel joining was performed using single mode fiber laser. Maximum power of the fiber laser is 100 W. The CCD(Charge- Coupled Device, CCD) camera to observe the specimen was made up. The objective was applied to micro joining system to make a small spot size of laser beam. In order to control the target position, micro-multi-axis-stage was set up. This paper presents results for the single mode fiber laser joining of micro wires.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.89-96
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• 2007

A volume integral equation method (VIEM) is applied for the effective analysis of plane elastostatic problems in unbounded solids containing single isotropic inclusion of two different shapes considering composite fiber volume fraction. Single cylindrical inclusion and single square cylindrical inclusion are considered in the composites with six different fiber volume fractions (0.25, 0.30, 0.35, 0.40, 0.45, 0.50). Using the rule of mixtures, the effective material properties are calculated according to the corresponding composite fiber volume fraction. The analysis of plane elastostatic problems in the unbounded effective material containing single fiber that covers an area corresponding to the composite fiber volume fraction in the bounded matrix material are carried out. Thus, single fiber, matrix material with a finite region, and the unbounded effective material are used in the VIEM models for the plane elastostatic analysis. A detailed analysis of stress field at the interface between the matrix and the inclusion is carried out for single cylindrical or square cylindrical inclusion. Next, the stress field is compared to that at the interface between the matrix and the single inclusion in unbounded isotropic matrix with single isotropic cylindrical or square cylindrical inclusion. This new method can also be applied to general two-dimensional elastodynamic and elastostatic problems with arbitrary shapes and number of inclusions. Through the analysis of plane elastostatic problems, it will be established that this new method is very accurate and effective for solving plane elastic problems in unbounded solids containing inclusions considering composite fiber volume fraction.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.04a
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• pp.388-399
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• 2003

Light losses in optical fibers are investigated by a fiber optic OTDR (Optical Time Domain Reflectometry) sensor system to develop fiber optic probes for structural strain measurement. The sensing fibers are manufactured 3 kinds of fibers: one is single mode fiber, and second is multimode fiber, and the third is low-cladding-index fiber. Fiber bending tests are performed to determine the strain sensitivity according to the strain of gage length of optical fibers. In the result of this experiments, the strain sensitivity of the single mode fiber was shown the highest value than others. The fiber optic strain probe was manufactured to verify the feasibility of the structural strain measurement. In this test, the fiber optic strain probe of the OTDR sensor could be easily made by the single mode fiber.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10b
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• pp.291-292
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• 2003

Although the tensile strength of textile materials are determined by that of their components, it is well known that the tensile strength of fiber bundles and yams is not accurately predicted from that of single-fibers by simple averaging methods or mathematical calculations, because of variations in their strength. Therefore, there have been attempts to interpret the bundle strength from that of its elements by the stochastical approach. (omitted)

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.201-204
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• 1999

Polarization mode dispersion (PMD) restrict the bend-width of single mode optical filer, and it is important parameter in the optical fiber having long-length. Although fiber has perfect circular symmetry, fiber bending, twisting and laws governing manufacture cause additional Polarization mode dispersion. The effect of polarization mode dispersion in general single mode fiber of long length is discussed in this paper. Measurement of PMD with random mode coupling were conducted in two kind of fibers using different laws governing manufacture and interferometric method.