• Journal of the Society of Disaster Information
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• v.11 no.2
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• pp.235-243
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• 2015

The methods to improve the protection and explosion-proof performance of concrete structures include the backside reinforcement or concrete material property improvement and the addition of structural members or supports to increase the resistance performance, but they are inefficient in terms of economics and structural characteristics. This study is about the basic study on the fiber composite panel cover, and the nano-composite material and adhesive as the filler, to maximize the specific performance of each layer and the protection and explosion-proof performance as the composite panel component by improving the tensile strength, light weight, adhesion and fire-proof performances. The fiber composite panel cover (aramid-polyester ratios of 6:4 and 6.5:3.5) had a 2,348 MPa maximum tensile strength and a 1.8% maximum elongation. The filler that contained the nano-composite material and adhesive had a 4 MPa maximum tensile shear adhesive strength. In addition, the nano-composite filler was 30% lighter than the normal portland cement

• Journal of the Korean Geosynthetics Society
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• v.12 no.1
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• pp.63-72
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• 2013

The structural stability of fill dam largely depends on the engineering behavior of rock materials used as main zone for dam construction and it is necessary to understand well the stress-strain characteristics of fill materials as well as shear strength property. In addition, the numerical analysis of fill dam requires a thorough study for calibrating material properties and parameters of a coarse-grained soil constitutive model. In this paper, large triaxial test results for Buhang-dam fill materials are analyzed and constitutive model parameters are calibrated based on the test results. It is shown that MD constitutive model is capable to predict the stress-strain behavior of dense and loose coarse-grained soils used for Buhang-dam construction based on the comparison study between the experimental test result and numerical simulation.

• Polymer(Korea)
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• v.24 no.5
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• pp.589-598
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• 2000

In this study, various unsaturated polyester (UPE) resins were prepared from the condensation polymerization of mixtures of saturated (isophthalic acid : IPA) and unsaturated (maleic anhydride : MA) dibasic acids with propylene glycol (PG), neopentyl glycol (NPG). The critical surface tension (Υ$_{c}$) for the surface characteristics of a solid were estimated by Zisman plot, and the structure-property relationship was investigated by measuring the rheology of resins. The values of Υ$_{c}$ for glass of solid were 30.5 mNㆍm$^{-1}$ for UPE resin liquids. As the content of NPG in a PG/NPG glycol mixture increased, both the contact angle and the surface tension of the UPE resin liquids were found to decrease. The dynamic viscoelasticities of UPE resins with different glycol molar ratios were also measured. Shear rate dependence of viscosity and angular frequency dependence of storage, and loss modulus tended to decrease with increasing NPG content.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.615-619
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• 2012

Recently, ultrafine grained (ufg, typically 100 > d > 500 nm) Ti-Fe eutectic materials have been highlighted due to their extraordinarily high strength and good abrasion resistance compared to conventional coarse grained (cg, d > $1{\mu}m$) materials. However, these materials exhibit limited plastic strain and toughness during room temperature deformation due to highly localized shear strain. Several approaches have been extensively studied to overcome such drawbacks, such as the addition of minor elements (Sn, Nb, Co, etc.). In this paper, we have investigated the influence of the addition of Gd and Y contents (0.3-1.0 at.%) into the binary Ti-Fe eutectic alloy. Gd and Y are chosen due to their immiscibility with Ti. Microstructural investigation reveals that the Gd phase forms in the eutectic matrix and the Gd phase size increases with increasing Gd content. The improvement of the mechanical properties is possibly correlated to the precipitation hardening. On the other hand, in the case of Ti-Fe-Y alloys, with increasing Y contents, primary phases form and lamellar spacing increases compared to the case of the eutectic alloy. Investigation of the mechanical properties reveals that the plasticity of the Ti-Fe-Y alloys is gradually improved, without a reduction of strength. These results suggest that the enhancement of the mechanical properties is closely related to the formation of the primary phase.

• Korean Journal of Human Ecology
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• v.16 no.5
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• pp.979-986
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• 2007

The purpose of this study is to investigate the dyeability, and the hand of soybean/cotton blended fabric after dyeing with natural and synthetic dyes. Soybean/cotton blended fabrics dyed with extracted solution from turmeric, sappan wood, gardenia and synthetic dyes(weak-acid dyes, reactive dyes, direct dyes). The hand value of soybean/cotton blended fabrics dyed with 6 different dyes was measured using Kawabata Evaluation System. The results are as follows; 1. The K/S value of the soybean/cotton blended fabric dyed with sappan wood extracts was the highest. 2. The color fastness of the soybean/cotton blended fabric dyed with reactive dyes was excellent. The fastness to the light of the same fabric was much better than the other fabrics. 3. Linearity of load-extension and tensile energy of the soybean/cotton blended fabric dyed with sappan wood extracts showed very high. Shear stiffness of the soybean/cotton blended fabric dyed with weak-acid dyes was much higher than that of fabric of dyed with reactive dyes. Bending property of the fabrics dyed with natural colorants(sappan wood, gardenia) showed very high, but that the fabric dyed with reactive dyes was very poor. 4. In the primary hand value, stiffness and anti-drape stiffness of the fabric dyed with weak-acid dyes showed the highest. Fullness and softness of the fabric dyed with weak-acid dyes showed very low.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.149-156
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• 2003

The development and maintenance of a sound bond are essential requirements of concrete repair and replacement. The bond property of a overlay to its substrate concrete during the lifetime is one of the most important performance requirements which should be quantified. A standard or a verified bond strength measurement method is required at field for screening, selecting materials and quality control for overlay or repair materials, but no test method has been adopted as a standard. In this study, a concrete pull off bond strength measurement method for field application is proposed and evaluated. This study compares the splitting tensile test, slant shear test, nipple pipe direct tensile test, flexural adhesion test, briquette tensile test, jumbo nail pull-out test and core pull-off test with their test procedures. From these comparison and investigation, core pull-off test is selected as a main topic of this study because of it's suitability for in situ testing, simplicities in field application and clearness at interface boundary condition. Thus, the proposed core pull off test is evaluated to be the most appropriate method for field application in a simple manner. The fracture surface and fracture mode could be easily determined by visual observation of failure surface of the field specimen. The core pull off test was found to be sensitive to surface condition and latex contents at latex modified concrete.

• Journal of the Korea Convergence Society
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• v.8 no.3
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• pp.185-190
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• 2017

This study investigates the bending stress, shear stress and deformation energy happening at the inner fiber structure when the bending moment is applied to he specimen with flat shape composed of carbon fiber. As CFRP is composed of innumerable fibers with multi-axes, the stress under bending condition can be effectively distributed. Theses stresses is shown to increase again at the starting point as this angle of $60^{\circ}$. Therefore, the condition at the stacking angle of $60^{\circ}$ is seen to become most adequate under the state where the bending stress happens. On the basis of this study result, the damage property by the bending at the plate due to stacking angle was examined through the analytic approach. it is thought that this study can be devoted to the safe design for damage prevention and durabilty improvement. Also, the esthetic sense can be shown as the designed factor of shape with flat plate is grafted onto the convergence technique.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.85-90
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• 2014

Ag paste has been used in the front electrode of the Si-solar cell. It is composed by Ag powder, glass frit, binder, solvent and dispersant. The role of the binder and the solvent is to make a flow and a printing property. However, it was not enough to report the printing properties with the variation of binder in the controled viscosity. In this study, we selected 3 kinds of typical binder which were used as binder for the paste in the industry, such as Ethyl cellulose, Hydroxypropyl cellulose and Acrylic. Ag pastes using these were prepared, controled viscosity and printed on the SiNx coated Si wafer. In the 'A paste' used Acrylic binder, printed hight was highest and 'H paste' used Hydroxypropyl cellulose binder was lowest. Because 'H paste' was high viscosity due to the molecular weight, the solvent was added in the paste to control the viscosity. Therefore, the content of solid was lower in 'H paste'. The relative pattern width which is related to the spreading of paste was the best in the case of 'H paste' and 'EH paste' at $30^{\circ}C$. It is thought that the optimization of the relative pattern width is possible for a paste by the controling shear thinning phenomenon. In the case of 'A paste', though printing hight was best, the pattern width was dependant on the temperature.

• Composites Research
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• v.23 no.6
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• pp.61-66
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• 2010

In this paper, the variation of mechanical properties of T800 carbon/epoxy composites according to the forming pressure, which was referred to previous studies on a filament winding process, were investigated. The specimens of all the tests were fabricated by an autoclave de-gassing molding process controlling forming pressure (absolute pressures of 0.1MPa, 0.3MPa, 0.7MPa including vacuum) and water jet cutting after fabricating composite laminates. Various tensile tests were performed for in-plane properties and interlaminar properties were also measured by using Iosipescu test jig. Fiber volume fraction was measured to correlate the property variation and the forming pressure. This properties are expected to be utilized in the design of Type III pressure vessel for hydrogen vehicles which uses the same carbon fiber (T800 carbon fiber) for the filament winding process.

• Composites Research
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• v.33 no.4
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• pp.213-219
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• 2020

Recently, global facing environmental issues have been raised caused by plastic waste. Hence, increasing the demand for interest in environmentally friendly materials. In this row, research on engineering composite materials also replacing the synthetic reinforcement by introducing natural fibers. However, focus on the strength and interfacial adhesion between matrix and reinforcement is very essential in natural fiber composite, which is insufficient in the literature. There are number of approaches for improving the mechanical strength of the composites, one of the common methods is to reinforce additive nanoparticles. The present investigation, bio-additives were synthesized utilizing bio-waste, cheap, bio-degradable sea-weed powder that could replace expensive nanomaterials and reinforced into the CFRP composite through Hand lay-up followed by a vacuum process. Mechanical properties were evaluated and analyzed through microanalysis. The results concluded that synthesized additives are effective for improving mechanical properties such as tensile, flexural, impact, and shear strength. Overall, the results confirmed that the fabricated composites have potential applications in the field of engineering applications.