• Electrical & Electronic Materials
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• v.8 no.4
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• pp.434-442
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• 1995

To improve dielectric and mechanical properties of insulating composite by plasma surface treatment, new plasma surface treatment process is designed with concentric and hemi-circle electrodes system. the plasma, which is generated between anode and cathode, is induced to the upper side of the electrode system and treats the surface of the insulators. The optimal surface treatment condition is that pressure : 0.5[torr], flux density : 100[gauss], discharge current : 500[mA] and treatment time : 3 minutes. The composite filled with glass cloth surface-treated by plasma shows the improvement in electric and mechanical properties, comparing non- and coupling agent treated samples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.9
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• pp.788-795
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• 2008

To understand the tensile behaviors of GFRP at low temperature, three types of specimen have been used in this study. Tensile properties and fracture mechanisms for three orthogonal orientations of plain weave glass fabric reinforced epoxy resin laminate were investigated at temperature range of about -30 to $15^{\circ}C$. The tensile properties of axial and edge type specimen decrease slightly with decreasing temperature to $-20^{\circ}C$. However, at $-30^{\circ}C$ the decreases in the tensile properties increased considerably. Below $-20^{\circ}C$, thickness type specimen showed a marked decreases in the tensile properties. It was obvious that the fracture manner of thickness type specimen was adhesive failure at above $-10^{\circ}C$ and a mixed adhesive and cohesive failure at below $-20^{\circ}C$.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.3
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• pp.15-21
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• 2009

The anisotropic mechanical properties were measured for the three orthogonal orientations of plain weave glass fabric reinforced epoxy resin laminate. In tensile and flexural tests, axial and edge type specimens failed by pull-out of warp and fill yarns, respectively. In contrast, the thickness type specimens failed by adhesive failure process. Longitudinal cracking occurred in several of the edge type specimens during tensile test. That cracking caused pop-in in the stress-strain curve. Defects induced by improper coupon machining caused that cracking.

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.5
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• pp.409-417
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• 2003

Cure monitoring can be used to improve the quality and productivity of thermosetting resin matrix composite products during their manufacturing process. In this work, the sensitivity of dielectrometry was improved by adequate separation the efforts of sensor and externals on the measured signal. A new algorithm to obtain the degree of cure during dielectric cure monitoring of glass/polyester and glass/epoxy composites was developed by employing a function of both temperature and dissipation factor, in which five cure monitoring parameters were used to calculate the degree of cure. The decreasing pattern of dissipation factor was compared with the relationships between the degree of cure and the resin viscosity. The developed algorithm might be employed for the in situ cure monitoring of thermosetting resin composites.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.2
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• pp.44-50
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• 2010

The behaviour of Modular GFRP(Glass Fiber Reinforced Polymers) decks for use in deteriorated bridge decks replacement are investigated experimentally in this study. As for the performance evaluation of bridge decks, experimental studies on the 3 test specimens with 1/5 scale of full size were carried out. Three specimens were sandwich plates with box tube cores. The constituents of bridge decks were glass fiber preforms and epoxy resin. The experimental results of all the specimens were summarized for maximum strength, stiffness and deformation capacity. A finite element analyses were compared to verify validity of experimental results.

• Composites Research
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• v.15 no.6
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• pp.30-37
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• 2002

A stiffness model has been proposed to predict elastic constants of twisted yam composites. The model is based upon the unit cell structure, the coordinate transformation, and the volume averaging of compliance constants for constituent materials. For the correlation of analytic results with experiments, composite samples of various yam twist angles were tested, and strength and Young's modulus under tensile, compressive, and shear loading have been obtained. The sample was fabricated by the RTM process using glass yarns and epoxy resin. The correlations of elastic constants showed relatively good agreements. The model provides the predictions of the three-dimensional engineering constants, which are valuable input data for the analytic characterization of textile composites made of twisted yam.

• Journal of the Korean Society for Nondestructive Testing
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• v.27 no.5
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• pp.409-416
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• 2007

In accordance with the increased usage of reinforcing materials such as carbon fibers and glass fibers, delamination detection between concrete and the reinforcing material is needed as such delaminations may be a major cause for strength reduction or failure of a structure. In this work, 15 GHz center frequency with 10 GHz band width horn antenna was used to detect delamination between concrete and carbon fibers or glass fibers. The specimens measured $600\;(length)\;{\times}\;600\;(width)\;{\times}\;100\;(thickness)\;mm$, and glass fibers and carbon fibers with a thickness of 1.5 mm were attached on the specimens' surfaces using epoxy. In addition, artificial delaminations of size $50\;(length)\;{\times}\;50\;(width)\;mm$ were placed in the middle of the specimen with thickness of 2, 4, 6 mm respectively together with a 2 mm delamination projecting upwards from the surface of the concrete. Therefore a total of 8 specimens were used, 4 specimens for glass fiber reinforced concrete and 4 for carbon fiber reinforced concrete, containing delaminations as described above. The experiment results were derived by using the difference of area under the curved graph. According to experimental results artifical delaminations were identified in both fiber reinforced and carbon reinforced specimens and these results could contribute to further development of delamination detection technology.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.421-431
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• 2007

The main purpose of this study is to develop a sprayed FRP repair and strengthening method, which is a new technique for strengthening the existing concrete structures by mixing one of the carbon or glass chopped fibers and one of the epoxy or vinyl ester resins with high-speed compressed air in open air and randomly spraying the mixture onto the concrete surface. At present, the sprayed FRP repair and strengthening method using the epoxy resin has not been fully discussed. In order to investigate the material property of the sprayed FRP, this study carried out tensile tests of the material specimens, which were changed with the combinations of various variables including the length of chopped fiber and the mixture ratio of chopped fiber and resin. These variables were set to have the equal material strength, compared with that of one layer of the FRP sheet. As a result, the optimal length of glass and carbon chopped fibers was fumed out to be 38 mm, and the optimal mixture ratio between chopped fiber and resin was also turned out to be 1 : 2 from each variable. And also, the thickness of the sprayed FRP to have the equal strength to one layer of the FRP sheet was finally calculated. In is study, a series of experiments were carried out to evaluate the strengthening effects of flexural beams, shear beams and damaged beams strengthened with the sprayed FRP method, respectively. The results revealed that the strengthening effects of the flexural and shear specimens were reasonably similar to those of the FRP sheet, and the developed Sprayed FRP technique is able to be used as a strengthening scheme of existing RC building.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.352-356
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• 2014

PDMS modified epoxy resin with epoxy group (EMPDMS) was prepared from the reaction of ${\alpha},{\omega}$-aminopropylpolydimethylsiloxane and diglycidyl ether of bisphenol-A (DGEBA) based epoxy resin, and PDMS modified epoxy hybrid compound (EMPDMSH) was prepared by introducing alkylesteraminopropyl alkoxy silane to EMPDMS. Their structures were characterized using FT-IR, $^1H$-NMR and $^{29}Si$-NMR. Coating materials were prepared by mixing EMPDMSH base and solvent. Physical properties of the coating materials coated on epoxy/glass fiber composite film were measured according to the content of PDMS in EMPDMSH. Contact angle of coating film was increased 30 to 71 degree. Adhesive property of coating film was 5B degree better then epoxy or acrylate coating materials, and surface roughness was decreased as increasing in EMPDMSH.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.6
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• pp.39-44
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• 2005

Due to mismatch of thermal expansion coefficients between aluminum sheet and glass/epoxy sheet, thermal residual stresses generally appear in the FML. These stresses will affect the yield and fatigue strength of the FML. The numerically determined residual stresses in the Fiber-Metal-Laminates(FML) have been compared to the residual stresses measured from the curvature and tensile test methods. These two experimental methods have been developed for assessing the influence of residual stress in FML. Post-stretching process has been applied to remove the thermal residual stress and reverse the stress distribution. After post-stretching process, the residual stress has been measured from experiments. The results obtained show that analytical and experimental data are well agreed. The thermal residual stress can be removed by post-stretching process and it will increase the yield strength of FML.