• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.35-38
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• 2003

In this paper, we investigated the electric and acoustic properties of piezoelectric composites, which were fabricated using polymer and piezoelectric ceramics, when the volume fraction of PZT varies. Practically, the shrinkage rate of polymer is an important factor in ultrasonic transducer fabrication. When 10 wt% filler A was added into polymer(Epofix), the lowest shrinkage was resulted. The electromechanical coupling factor($k_t$) of the fabricated piezoelectric composites showed its highest when the volume fraction PZT was 0.6. It decreased if the volume fraction was higher than the value. The relative permittivity and acoustic impedance of piezoelectric composites decreased linearly when PZT volume fraction was decreased. The lowest acoustic impedance was 3.2 when the volume fraction of PZT was 0.2.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.59-62
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• 2003

Kinds, shapes and fraction ratios of fibers have influence on properties of HPFRCC(High-Performance Fiver Reinforced Cementitious Concrete ) like bending strength, strain capacity and fracture toughness. For example, hydrophilic fibers have different chemical bond strength from hydrophobic fibers, fiber shapes influence on fiber pull-out and rupture, and fiber volume fraction influence on bending strength. In this study, to estimate influences of kinds, shapes and fraction ratios of fibers, we make HFRCC with 3 kind of fiber in various volume fraction of fiber and compare cracking, bending strength and fracture toughness. As the results, bending strength of HPFRCC was increased as fiber volume fraction was Increase and fiber tensile strength was increase, and strain capacity and fracture toughness of HFRCC was higher in fiber pull-out fracture than in fiber rupture fracture. And HFRCC showing pseudo strain hardening has higher fiber reinforce efficiency than others.

• Progress in Superconductivity and Cryogenics
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• v.18 no.3
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• pp.6-9
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• 2016

The enhancement of mechanical properties of coated conductor (CC) tapes in practical application are usually achieved by reinforcing through lamination or electroplating metal layers on either sides of the CC tape. Mechanical or electromechanical properties of the CC tapes have been largely affected by the lamination structure under various loading modes such as tension, bending or even cyclic. In this study, the influence of brass laminate volume fraction on electromechanical properties of RCE-DR processed Gadolinium-barium-copper-oxide (GdBCO) CC tapes was investigated. The samples used were composed of single-side and both-side laminate of brass layer to the Cu-stabilized CC tape and their $I_c$ behaviors were compared to those of the Cu-stabilized CC tape without external lamination. The stress/strain dependences of $I_c$ in laminated CC tapes under uniaxial tension were analyzed and the irreversible stress/strain limits were determined. As a result, the increase of brass laminate volume fraction initially increased the irreversible strain limit and became gradual. The corresponding irreversible stress limit, however, showed no difference even though the brass laminate volume fraction increased to 3.4. But the irreversible load limit linearly increased with the brass laminate volume fraction.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.3
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• pp.454-460
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• 2015

The present study is undertaken to evaluate the effect of volume fraction on the results of Charpy impact test for the rubber matrix filled with nano sized silica particles composites. The Charpy impact tests are conducted in the temperature range $0^{\circ}C$ and $-10^{\circ}C$. The range of volume fraction of silica particles tested are between 11% to 25%. The critical energy release rate $G_{IC}$ of the rubber matrix composites filled with nano sized silica particles is affected by silica volume fraction and it is shown that the value of $G_{IC}$ decreases as volume fraction increases. In regions close to the initial crack tip, fracture processes such as matrix deformation, silica particle debonding and delamination, and/or pull out between particles and matrix which is ascertained by SEM photographs of Charpy impact fracture surfaces.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.3
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• pp.85-94
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• 2006

Practially useful method of steel fiber for construction work is presented in this study. The most important purpose of this study is to develop a model which can predict mechanical behavior of the structure according to aspect ratio and volume fraction of steel fiber. Experiments on compressive strength, elastic modulus, and splitting strength were performed with self-made cylindrical specimens of variable aspect ratios and volume fractions. The experiment showed that compressive strength was not in direct proportion to volume fraction which doesn't seem to have great influence over compressive strength. However, splitting strength showed almost direct proportion to aspect ratio and volume fraction. Improvement of optimal efficiency was confirmed when the aspect ratio was 70. Experiments on flexural strength, fracture energy, and characteristic length were carried out with self-manufactured beams with notch. As a result, increases of flexural strength, fracture energy, and characteristic length according to increase of volume fraction tend to be prominent when aspect ratio is 70. The steel fiber improves concrete to be more ductile and tough. Moreover, regression analysis was the performed and predictable model was developed after determining variables. With comparison and analysis of suggested estimated values and measured data, reliance of the model was verified.

• Carbon letters
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• v.3 no.3
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• pp.127-132
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• 2002

Unidirectional polymer composites were prepared using high-strength carbon fibers as reinforcement and phenolic resin as matrix precursor with keeping fiber volume fraction at 30, 40, 50 and 60% respectively. These composites were carbonized at $1000^{\circ}C$ and graphitised at $2600^{\circ}C$ in the inert atmosphere. The carbonized and graphitised composites were characterized for mechanical properties as well as microstructure. Microscopic studies were carried out of the polished surface of carbonized and graphitised composites after etching by chromic acid, to understand the effect of fiber volume fraction on oxidation at fiber-matrix interface. It is found that the flexural strength in polymer composites increases with fiber volume fraction and so does for the carbonised composites. However, the trend was found to be reversed in graphitised composites. In all the carbonized composites anisotropic region has been observed at fiber-matrix interface which transforms into columnar type microstructure upon graphitisation. The extension of strong and weak columnar type microstructure is function of fiber volume fraction. SEM microscopy of the etched surface of the sample reveal that composites containing 40% fiber volume has minimum oxidation at the interface, revealing a strong interfacial bonding.

• 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.

• Advances in concrete construction
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• v.13 no.5
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• pp.367-376
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• 2022

Theoretical study of vibration distinctiveness of rotating cylindrical are examined for three volume fraction laws viz.: polynomial, exponential and trigonometric. These laws control functionally graded material composition in the shell radius direction. Functionally graded materials are controlled from two or more materials. In practice functionally graded material comprised of two constituent materials is used to form a cylindrical shell. For the current shell problem stainless steel and nickel are used for the shell structure. A functionally graded cylindrical shell is sanctioned into two types by interchanging order of constituent materials from inner and outer side for Type I and Type II cylindrical shell arrangement. Fabric composition of a functionally graded material in a shell thickness direction is controlled by volume fraction law. Variation of power law exponent brings change in frequency values. Influence of this physical change is investigated to evade future complications. This procedure is capable to cater any boundary condition by changing the axial wave number. But for simplicity, numerical results have been evaluated for clamped- simply supported rotating cylindrical shells. It has been observed from these results that shell frequency is bifurcated into two parts: one is related to the backward wave and other with forward wave. It is concluded that the value of backward frequency is some bit higher than that forward frequency. Influence of volume fraction laws have been examined on shell frequencies. Backward and forward frequency curves for a volume fraction law are upper than those related to two other volume fraction laws. The results generated furnish the evidence regarding applicability of present shell model and also verified by earlier published literature.

• Composites Research
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• v.26 no.4
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• pp.218-222
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• 2013

This study demonstrated that a slag, an industrial solid waste, can be used as a structural reinforcement. The mechanical properties(tensile strength and Elastic modulus) of slag reinforced composite(SRC) was investigated as functions of slag particle size (8~12 ${\mu}m$ and 12~16 ${\mu}m$) and volume fraction (0-40 vol.%). In order to investigate the interface and a degree of particle dispersion which have an effect on mechanical properties, optical microscopic images were taken. The results of tensile tests showed that the tensile strength decreased with an increase in slag volume fraction and particle size. The elastic modulus increased with an increase in slag volume fraction and particle size except for 30 vol.% SRC. The tensile strength decreased with an increase in slag particle size. The microscopic picture showed SRC has fine degree of particle dispersion at low slag volume fraction. SRC has a good interface at every volume fraction. However particle cluster was incorporated with an increase in slag volume fraction.

• Korean Journal of Materials Research
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• v.29 no.4
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• pp.211-220
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• 2019

In this study, three kinds of bainitic steel plates are manufactured by varying the chemical compositions and their microstructures are analyzed. Tensile and Charpy impact tests are performed at room and low temperature to investigate the correlation between microstructure and mechanical properties. In addition, heat affected zone (HAZ) specimens are fabricated by a simulation of welding processes, and the HAZ microstructure is analyzed. The base steel that has the lowest carbon equivalent has the highest volume fraction of acicular ferrite and the lowest volume fraction of secondary phases, so the strength is the lowest and the elongation is the highest. The Mo steel has a higher volume fraction of granular bainite and more secondary phases than the base steel, so the strength is high and the elongation is low. The CrNi steel has the highest volume fraction of the secondary phases, so the strength is the highest and elongation is the lowest. The tensile properties of the steels, namely, strength and elongation, have a linear correlation with the volume fraction of secondary phases. The Mo steel has the lowest Charpy impact energy at $-80^{\circ}C$ because of coarse granular bainite. In the Base-HAZ and Mo-HAZ specimens, the hardness increases as the volume fraction of martensite-austenite constituents increases. In the CrNi-HAZ specimen, however, hardness increases as the volume fraction of martensite and bainitic ferrite increases.