• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.09a
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• pp.43-46
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• 2001

The DC dielectric breakdown of epoxy composites used for transformer was experimented and then its data were simulated by Weibull distribution equation in this study. The more hardener increased the stronger breakdown strength at low temperature because of cross-linked density by the virtue of ester radical, and the breakdown strength of specimens with filler was lower than it of non-filler specimens because it was believed that the adding filler formed interface, charges were accumulated in it, the molecular mobility was raised, the electric field was concentrated, electrons were accelerated and then electron avalanche was early accomplished. From the analysis of Wei bull distribution equation, it was confirmed that as the allowed breakdown probability was· given by 0.1[%], the value of 'applied field was needed to be under 17.20[kV/mm].

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.3
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• pp.167-173
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• 1998

In order to estimate the life time of epoxy composites used for modeling material of transformer, the AC breakdown experiments of it were experimented and then the AC breakdown data were also simulated by Weibull distribution equation in this study. The life time of H100F65 specimen was the shortest and it of SH100F65 specimen was the longest, and as the AC voltage was applied to specimen for 50[min], the breakdown probability of each specimen was 31.2[%], 17.00[%], 84.36[%] and 12.35[%], respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.32-32
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• 2010

A epoxy/multilayered silicate nanocomposite was prepared by a new AC electric application method and micro silica particle was poured into the nanocomposite in order to prepare epoxy/micro-and-nano- mixed composites (EMNC). Electric insulation breakdown strength was measured in a sphere-sphere electrode system designed for the prevention of edge breakdown and the data were estimated by Weibull plot. As the exfoliated silicate nano-plates were homogeniously dispersed in the micro silica particles, the insulation property was higherd.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1386-1388
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• 2003

In this study. the fatigue behavior of cracked aluminum repaired by unidirectional graphite/epoxy composites was experimentally investigated. The aluminum used was 7075-T6 and the patch used was four plied unidirectional ([0]$_4$) composites. The composite patch was adhesively bonded to the cracked aluminum using secondary bonding procedure. Two different specimens of cracked aluminum and cracked aluminum repaired with patch were used in the fatigue tests. Load ratio and the frequency applied in the fatigue tests were 0 and 10 Hz, respectively. The results showed that the fatigue behavior of cracked aluminum was improved by repairing the cracked area with composite patch. Specifically, the specimen repaired by composite patch showed 30% more improved fatigue behavior than regular specimen.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.758-763
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• 2000

Dielectric strength of insulators made of epoxy composites rapidly decreases due to ageing to interfaces between the matric resin and filler particles. The adhesion variation of interfaces caused by moisture absorption also alters electrical properties that are the basic characteristics of insulators, particularly, in outdoor use. In this paper, electrical properties of epox/SiO$_2$composites were investigated at boiling absorption condition to observe the influences of moisture. In order to analyze the basic physical properties of samples, scanning electron microscopy and DC, AC and impulse voltage dielectric strength were measured. Also, the breakdown time of samples was measured under AC 6[kV] applied voltage, and the variation of lifetime was verified by using Weibull distribution function.

• Proceedings of the KIEE Conference
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• 2000.11c
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• pp.485-487
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• 2000

Dielectric strength of insulators made of epoxy composites rapidly decreases due to ageing to interfaces between the matrix resin and filler particles. The adhesion variation of interfaces caused by moisture absorption also alters electrical properties that are the basic characteristics of insulators, particularly, in out door use. In this paper, electrical properties of epoxy/$SiO_2$ composites were investigated at boiling absorption condition to observe that influence of moisture. The breakdown time of samples were measured under AC 6[kV] applied voltage, and the variation of lifetime was varified by using Weibull distribution function.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.526-528
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• 1999

Epoxy resin has been used as matrix resin of advanced composites owing to ideally suitable properties and inherent physical and chemical properties for electrical and electronic insulation In this paper, in order to evaluate the performance of epoxy composites for out door insulation, variations of tracking resistance were investigated on the moisture absorption aging condition. Also, IPN methods were introduced in order to improve performance for out door use. As a result, it was confirmed that tracking resistance were degraded with boilling time. But, it was confirmed that specimen of IPN structure and KC-335 have the better tracking resistance properties than SIN structure by moisture absorption aging

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.360-363
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• 1997

The method of estimating life time of epoxy composites which be widely used for transformers has been studied in this paper. The breakdown properties of specimens are observed by appling high AC voltage at the room temperature from a series of the experiments. Afterwards, the breakdown time was determined under the constant voltage below the lowest breakdown voltage. Also, V-t properties were found out using weibull distribution widely used in the applications of discrete data for estimating life time of epoxy composites and life exponent n was gained properly. when life exponent is gained is found out, the tong breakdown life time at used voltage can be estimated from breakdown experiments in short time using reverse law of n power.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.53-56
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• 2002

External low-velocity impact loadings onto the composites cause reduction of stiffness and/or strength. The reductions indicate that internal(external) damages were developed within the composites. These damages could be matrix cracking, fiber/matrix debonding, or delamination between layers. In previous studies, damage evaluation have been done by applying secondary mechanical loading such as buckle-driven compressive, or fatigue, or flexural loadings. An evaluation method by applying indentation loadings on the composites was proposed. The load-displacement curves obtained from the indentation testing provided the extent of damages within the composites due to impact loadings.

• Composites Research
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• v.26 no.3
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• pp.165-169
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• 2013

This work presents the tensile properties and water uptake behavior of plasma treated abaca fibers reinforced epoxy composites. The composites were prepared by vacuum assisted resin transfer molding. The effects of treatment on tensile properties and sorption characteristics of abaca fiber composites in distilled water and salt solution at room temperature were investigated. The tensile strength of the composites increased with plasma treatment. With plasma treatment, an improvement of 92.9% was obtained in 2.5 min exposure time in plasma. This is attributed to high fiber-matrix compatibility. Less improvement on tensile properties of hybrid treatment of sodium hydroxide and plasma was obtained. However, both treatments reduced overall water uptake in distilled water and salt solution. Hydrophilicity of the fibers decreased upon plasma and sodium hydroxide treatment, which decreases water uptake.