• Computers and Concrete
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• 제11권6호
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• pp.531-539
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• 2013

An experimental investigation of mechanical properties of jute fiber-reinforced concrete (JFRC) has been reported for making a suitable construction material in terms of fiber reinforcement. Two jute fiber reinforced concretes, called jute fiber reinforced normal strength concrete (JFRNSC) and jute fiber-reinforced high-fluidity concrete (JFRHFC), were tested in compression, flexure and splitting tension. Compressive, flexural and splitting tensile strengths of specimens were investigated to four levels of jute fiber contents by volume fraction. From the test results, Jute fiber can be successfully used for normal strength concrete (NSC) and high-fluidity concrete (HFC). Particularly, HFC with jute fibers shows relatively higher improvement of strength property than that of normal strength concrete.

• 전기학회논문지
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• 제62권2호
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• pp.219-227
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• 2013

This paper reported a study on the thermal, mechanical and electrical insulation properties of epoxy/mica composites. To investigate the effect of mica content, glass transition temperature, mechanical properties such as tensile and flexural strength, and insulation breakdown properties for epoxy composites with various contents of mica. The effect of insulation thickness on insulation breakdown property was also studied. It was observed that tensile and flexural strength decreased with increasing mica content, while elastic modulus increased as the mica content increased. AC insulation breakdown strength for all epoxy/mica composites was higher than that of neat epoxy and that of the system with 20 wt% mica was 14.4% improved. As was expected, insulation breakdown strength at $30^{\circ}C$ was far higher than that at $130^{\circ}C$, and it was also found that insulation breakdown strength was inversely proportion to insulation thickness.

• 대한전기학회논문지
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• 제34권8호
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• pp.323-330
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• 1985

Dielectric loss tangent and ac dielectric strength of GFRP (Glass Fiber Reinforced Plastics, G-10)was investigated as parameters of mechanical and thermal stresses, in order to study the basic dielectrical characteristics of composite insulating materials. The dielectric loss tangent was increased and the ac dielectric strength was decreased with increase in the mechanical stresses beyond the mechanical yield point on account of fiber-matrix debonding, but the dielectric constant was not varied sigificantly. the dielectric strength of G-10 was about 2 MV/cm and the dielectric constant was about 4.8.

• Geomechanics and Engineering
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• 제36권2호
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• pp.145-156
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• 2024

The mechanical properties of the concrete-frozen soil interface play a significant role in the stability and service performance of construction projects in cold regions. Current research mainly focuses on the precast concrete-frozen soil interface, with limited consideration for the more realistic cast-in-place concrete-frozen soil interface. The two construction methods result in completely different contact surface morphologies and exhibit significant differences in mechanical properties. Therefore, this study selects silty clay as the research object and conducts direct shear tests on the concrete-frozen soil interface under conditions of initial water content ranging from 12% to 24%, normal stress from 50 kPa to 300 kPa, and freezing temperature of -3℃. The results indicate that (1) both interface shear stress-displacement curves can be divided into three stages: rapid growth of shear stress, softening of shear stress after peak, and residual stability; (2) the peak strength of both interfaces increases initially and then decreases with an increase in water content, while residual strength is relatively less affected by water content; (3) peak strength and residual strength are linearly positively correlated with normal stress, and the strength of ice bonding is less affected by normal stress; (4) the mechanical properties of the cast-in-place concrete-frozen soil interface are significantly better than those of the precast concrete-frozen soil interface. However, when the water content is high, the former's mechanical performance deteriorates much more than the latter, leading to severe strength loss. Therefore, in practical engineering, cast-in-place concrete construction is preferred in cases of higher negative temperatures and lower water content, while precast concrete construction is considered in cases of lower negative temperatures and higher water content. This study provides reference for the construction of frozen soil-structure interface in cold regions and basic data support for improving the stability and service performance of cold region engineering.

• 대한기계학회논문집A
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• 제26권3호
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• pp.570-575
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• 2002

It is well-known that the bond strength between CFRP(Carbon Fiber Reinforced Plastic) and aluminum is significantly affected by the surface treatment of the CFRP and the aluminum. This study investigates the surface treatment of CFRP to improve the T-peel strength of CFRP/aluminum composites. The surface of %CFRP([0^0]_{14})$ was treated by the ion assisted reaction method under oxygen environment. T-peel strength tests were performed based on the procedure of ASTM D1876-95. The T-peel strength of surface-treated CFRP/aluminum composites was compared with that of untreated CFRP/aluminum composites. The results showed that the T-peel strength of surface-treated CFRP/aluminum composites was about 5.5 times higher than that of untreated CFRP/aluminum composites. SEM examination showed that the improvement of T-peel strength was attributed to the uniform spread and fracture of epoxy adhesive.

• 한국재료학회지
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• 제28권10호
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• pp.601-609
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• 2018

To study the effects of graphite shape and the composite fabricating method on the mechanical properties of graphite/copper (Gr/Cu) composites, a copper composite using graphite flakes or graphite granules as reinforcing phases is fabricated using mechanical mixing or electroless plating method. The mechanical properties of the Gr/Cu composites are evaluated by compression tests, and the compressive strength and elongation of the Gr/Cu composites using graphite granules as a reinforcing phase are compared with those of Cu composites with graphite flakes as a reinforcing phase. The compressive yield strength or maximum strength of the Gr/Cu composites with graphite granules as a reinforcing phase is higher than that of the composites using graphite flakes as a reinforcing phase regardless of the alignment of graphite. The strength of the composite produced by the electroless plating method is higher than that of the composite material produced by the conventional mechanical mixing method regardless of the shape of the graphite. Using graphite granules as a reinforcing phase instead of graphite flakes improves the strength and elongation of the Gr/Cu composites in all directions, and reduces the difference in strength or elongation according to the direction.

• 한국염색가공학회지
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• 제31권4호
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• pp.354-362
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• 2019

In order to apply thermoplastic composites using PETG resin to various industrial fields such as bicycle frames and industrial parts, it is necessary to verify the impact resistance, durability and mechanical properties of the manufactured composite materials. To improve the mechanical properties, durability and impact resistance of PETG resin, an amorphous resin, in this study, compound and injection molding process were carried out using various additives such as TiO2, carbon black, polyolefin elastomer, and PETG amorphous resin. The thermal and mechanical properties of the thermoplastic composites, and the Charpy impact strength. The analysis was performed to evaluate the characteristics according to the types of additives. DSC and DMA analyzes were performed for thermal properties, and tensile strength, flexural strength, and tensile strength change rate were measured using a universal testing machine to evaluate mechanical properties. Charpy impact strength test was conducted to analyze the impact characteristics, and the fracture section was analyzed after the impact strength test. In the case of POE material-added thermoplastic composites, thermal and mechanical properties tend to decrease, but workability and impact resistance tend to be superior to those of PETG materials.

• Structural Engineering and Mechanics
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• 제46권2호
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• pp.295-322
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• 2013

Steel fiber reinforced self-compacting concrete (SFRSCC) is a relatively new composite material which congregates the benefits of self-compacting concrete (SCC) technology with the profits derived from the fiber addition to a brittle cementitious matrix. Steel fibers improve many of the properties of SCC elements including tensile strength, toughness, energy absorption capacity and fracture toughness. Modification in the mix design of SCC may have a significant influence on the SFRSCC mechanical properties. Therefore, it is vital to investigate whether all of the assumed hypotheses for steel fiber reinforced concrete (SFRC) are also valid for SFRSCC structures. Although available research regarding the influence of steel fibers on the properties of SFRSCC is limited, this paper investigates material's mechanical properties. The present study includes: a) evaluation and comparison of the current analytical models used for estimating the mechanical properties of SFRSCC and SFRC, b) proposing new relationships for SFRSCC mixtures mechanical properties. The investigated mechanical properties are based on the available experimental results and include: compressive strength, modulus of elasticity, strain at peak compressive strength, tensile strength, and compressive and tensile stress-strain curves.

• 대한건축학회논문집:구조계
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• 제35권5호
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• pp.153-160
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• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• 한국재료학회지
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• 제14권8호
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• pp.579-586
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• 2004

A study on the effects of oxide growth on the mechanical properties degradation of pure zirconium and Zircaloy-4 is carried out with high temperature tensile tests. It is found that the mechanical properties can deteriorate with the oxide growth less than $1\%$ of total specimen cross section, especially at $300\~400^{\circ}C$ that is zirconium alloy cladding temperature during the nuclear reactor operation. It is also revealed that Young's modulus changes little but yield strength and tensile strength drop down to $20\% and 40\%$ of the room temperature strength, respectively, in the temperature range. Fractographic analysis shows that the number of dimples decreases and fractured surface becomes smooth with increasing oxide thickness.