• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.237-240
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• 2002

Amino terminated polyetherimide(ATPEI) has been synthesized by bisphthalic anhydride arid m-phenylenediamine, after that characterized by differential scanning calorimetry(DSC), thermogravimetric analyzer(TGA). Fourier transform (FT-IR) spectroscopy and gel permeation chromatography(GPC). ATPEI was blend to improve the toughness of bisphenol-A type epoxy resin which was cured by nadic methyl anhydride(NMA). The fracture toughness and the molphology of the toughened epoxy resin was evaluated. The toughness of ATPEI modified epoxy resin was higher than that of the PEI modified epoxy resin. In addtion, carbon fiber/ATPEI modified epoxy resin composites were fabricated and the mechanical properties of the resulted composites were investigated.

• Composites Research
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• v.28 no.6
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• pp.361-365
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• 2015

The influence of MWCNTs on fracture toughness properties of MWCNTs/Nickel-Pitch Fibers/epoxy composites (MWCNTs/Ni-PFs/epoxy) was investigated according to MWCNTs content. Nickel-Pitch-based carbon fibers (Ni-PFs) were prepared by electroless nickel-plating. The surface properties of Ni-PFs were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS). The fracture toughness of MWCNTs/Ni-PFs/epoxy was assessed by critical stress intensity factor ($K_{IC}$) and critical strain energy release rate ($G_{IC}$). From the results, it was found that the fracture toughness properties of MWCNTs/Ni-PFs/epoxy were enhanced with increasing MWCNTs content, whereas the value decreased above 5 wt.%. MWCNTs content. This was probably considered that the MWCNTs entangled with each other in epoxy due to an excess of MWCNTs.

• Composites Research
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• v.28 no.6
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• pp.389-394
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• 2015

The sound absorption coefficient and sound transmission loss of graphite intercalation compound (GIC) included epoxy composites were investigated. Epoxy resin was infused into the expanded GIC and the impedance tube method was employed to measure the sound absorption coefficient and sound transmission loss. Scanning electron microscopy photographs showed uniform distribution of the GIC in the epoxy matrix. The surface density of epoxy/GIC (20 wt%) composites decreased about 56% compared to that of pure epoxy. The sound absorption coefficient of composites increased about 3 times at the frequency range of 500~1000 Hz compared to the pure epoxy. The sound transmission loss of composites decreased with increasing the GIC content and it is attributed to the increase of pores in the composites.

• Journal of Powder Materials
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• v.30 no.4
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• pp.346-355
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• 2023

Epoxy-based composites find extensive application in electronic packaging due to their excellent processability and insulation properties. However, conventional epoxy-based polymers exhibit limitations in terms of thermal properties and insulation performance. In this study, we develop epoxy-based siloxane/silica composites that enhance the thermal, mechanical, and insulating properties of epoxy resins. This is achieved by employing a sol-gel-synthesized siloxane hybrid and spherical fused silica particles. Herein, we fabricate two types of epoxy-based siloxane/silica composites with different siloxane molecular structures (branched and linear siloxane networks) and investigate the changes in their properties for different compositions (with or without silica particles) and siloxane structures. The presence of a branched siloxane structure results in hardness and low insulating properties, while a linear siloxane structure yields softness and highly insulating properties. Both types of epoxy-based siloxane/silica composites exhibit high thermal stability and low thermal expansion. These properties are considerably improved by incorporating silica particles. We expect that our developed epoxy-based composites to hold significant potential as advanced electronic packaging materials, offering high-performance and robustness.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1237-1240
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• 2010

The mechanical properties of multiwalled carbon nanotubes (MWNTs)-reinforced epoxy matrix composites with different weight percentages of MWNTs have been investigated. Also, the morphologies and failure behaviors of the composites after mechanical tests are studied by SEM and TEM analyses. As a result, the addition of MWNTs into the epoxy matrix has a remarkable effect on the mechanical properties. And the fracture surfaces of MWNTs/epoxy composites after flexural strength tests show different failure mechanisms for the composites under different nanotube contents. Also, a chemical functionalization of MWNTs can be a useful tool to improve the dispersion of the nanotubes in an epoxy system, resulting in increasing the mechanical properties of the composite materials studied.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.497-502
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• 2003

This study intends to provide the analytical and experimental damping characterization of carbon nanotube/epoxy composites. A constitutive model based on continuum mechanics is employed to describe epoxy and the perfectly bonded and partially bonded nanotubes. An interfacial stick-slip between the nanotubes and epoxy is considered to characterize the damping of the composites. For experimental estimation, beam-type specimens are prepared with a variation of nanotube concentration from 0.5% to 2% in weight. An ultrasonic agitation method is employed for enhancing the nanotube dispersion within epoxy. Damping of the composites is characterized in terms of the strain and the nanotube concentration. Results show that the nanotube concentration significantly affects the damping characteristics of the nanocomposites. A good correlation is found between the analytical prediction based on the stick-slip and the experimental measurements.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.557-563
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• 2010

Mode II interlaminar fracture toughness was measured and fractured surfaces were observed of carbon/epoxy and glass/epoxy woven fabric composites for carbody structure. Woven fabric carbon/epoxy and glass/epoxy composites that made with prepreg and epoxy resin(RS1222) are used in carbody structure of Korean tilting train(TTX) and low floor bus. ENF(End Notched Flexure) specimens having $120mm{\times}20m{\times}5mm$ shape and 35mm initial crack were made with each composites and three point bending tests according to ASTM D790 were conducted for these specimens. Crack lengths in tests were recorded using optical microscope and digital camcorder. NL(Non Linear), 5% offset and Max. load points in load -displacement curves were checked and mode II interlaminar fracture toughness of these points were calculated and compared. Fractured surfaces of specimens were observed using optical microscope and mode II delamination behavior of each composites was discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.796-802
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• 2016

In order to develop an electrical insulation material for gas GIS (insulation switch gear) spacer, 4 types of epoxy/micro-alumina (40, 50, 60, 70 wt%) composites and 9 types of epoxy/nano-alumina (1, 3, 5 g)/micro-alumina (40, 50, 60, 70 wt%) composites were prepared and tensile test was carried out. In here, nano-alumina was previously surface-treated with GDE (glycerol diglycidyl ether). As micro-alumina and GDE-treated nano-alumina contents increased, tensile strength increased and the highest value was shown in the system with 3 g GDE-treated nano-alumina.

• Proceedings of the Korean Society of Computer Information Conference
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• 2011.06a
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• pp.351-354
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• 2011

The electrical degradation phenomena of epoxy composites to be used as a molding material for transformers were studied. The electrets were first manufactured by applying high voltages to five kinds of specimens given a mixing rate, and then TSC(Thermally Stimulated Current) values at the temperature range of $-160{\sim}200[^{\circ}C]$ were measured from a series of experiments. The behaviour of carrier and its origin in epoxy composites were examined, respectively. And various effects of electrical degradation on epoxy composites were also discussed in this study.

• Steel and Composite Structures
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• v.33 no.2
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• pp.299-306
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• 2019

The natural fibre composites are termed as bio-composites. They have shown a promising replacement to the current carbon/glass fibre reinforced composites as environmental friendly materials in specific applications. Natural fibre reinforced composites are potential materials for various engineering applications in automobile, railways, building and Aerospace industry. The natural fibre selected to fabricate the composite material is plant-based fibre e.g., sisal fibre. Sisal fibre is a suitable reinforcement for use in composites on account of its low density, high specific strength, and high hardness. Epoxy is a thermosetting polymer which is used as a resin in natural fibre reinforced composites. Hand lay-up technique was used to fabricate the composites by reinforcing sisal fibres into the epoxy matrix. Composites were prepared with the unidirectional alignment of sisal fibres. Test specimens with different fibre orientations were prepared. The fabricated composites were tested for mechanical properties. Impact test, tensile test, flexural test, hardness test, compression test, and thermal test of composites had been conducted to assess its suitability in industrial applications. Scanning electron microscopy (SEM) test revealed the microstructural information of the fractured surface of composites.