• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.149-149
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• 2003

This paper presents the work peformed in a program developing composite material which properties satisfy structural and thermal requirements for aircrafts and spacecrafts. In the aerospace vehicle structures, the specific strength of the materials is one of the important requirements and this is why polymer matrix composite material with reinforced carbon fiber is widely used. However, the mechanical properties of the composite material have been known to be dependent on processing and this difficulties in evaluation have caused a lot of mechanical tests for each batch.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1356-1363
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• 2009

The aim of this research is to construct eigenfrequency optimization codes for plates with Arbitrary Rank Microstructures. From among noise factors, resonance sound is main reason for floor's solid noise. But, Resonance-elusion design codes are not fixed so far. Besides, The prediction of composite material's capability and an resonance elusion by controlling natural frequency of plate depend on designer's experiences. In this paper, First, using computer program with arbitrary rank microstructure, variation on composite material properties is studied, and then natural frequency control is performed by plate topology optimization method. The results of this study are as followed. 1) Programs that calculate material properties along it's microstructure composition and control natural frequency on composite material plate are coded by Homogenization and Topology Optimization method. and it is examined by example problem. 2) Equivalent material properties, calculated by program, are examined for natural frequency. In this paper, Suggested programs are coded using $Matlab^{TM}$, Feapmax and Feap Library with Homogenization and Topology Optimization method. and Adequacy of them is reviewed by performing the maximization or minimization of natural frequency for plates with isotropic or anisotropic materials. Since the programs has been designed for widely use. If the mechanism between composite material and other structural member is identified, extension application may be possible in field of structure maintenance, reinforcement etc. through application of composite material.

• Composites Research
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• v.36 no.3
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• pp.193-198
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• 2023

Currently, there are many discussions about composite materials and 3D printed composite material to weight reduction of ships. A test was conducted to confirm the applicability of the 3D printed composite material to ships and offshore structures by linking the 3D printing technology with excellent productivity and the composite material with corrosion resistance and lightweight characteristics in salt water environments. In order to apply the 3D printed composite material used in this paper to ships and offshore structures, the temperature environmental effects that can be exposed in the marine environment should be considered. Therefore, the tensile test was conducted with specimen of Carbon + Onyx, Carbon + Nylon, HSHT glass + Onyx, HSHT glass + Nylon material in low temperature (-50℃), room temperature (20℃), and high temperature (50℃) environments that can be exposed to the marine environment. As a result of the tensile test, the carbon + onyx specimen showed the highest tensile strength and the HSHT glass + onyx specimen showed the highest tensile strain. In addition, by analyzing the tested specimens, the failure mode of the 3D printed composite material specimens exposed to various temperature environments was analyzed.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.245-248
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• 2005

During manufacturing thick composite cylinders, large thermal residual stresses are developed and induce catastrophic interlaminar failures. Since the residual stresses are dependent on many process parameters, such as temperature distribution during cure, cure shrinkage, winding tension, and migration of fibers, calculation of the residual stresses is very difficult. Therefore a radial-cut method have been used to measure the residual stresses in the composite cylinders. But the conventional radial-cut method needs to know numerous material properties which are not only troublesome to obtain but also vary with change of fiber arrangement during consolidation. In this paper, a new radial-cut method with cut-cylinder-bending test was proposed and the measured residual stresses were compared with calculated thermal residual stresses. It was found that the new radial-cut method which does not need to know any of material properties gave better estimation of residual stresses regardless of radial variation of material properties. Additionally, interlaminar tensile strength could be obtained by the cut-cylinder-bending test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1989.06a
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• pp.63-65
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• 1989

Piezoelectric BaTiO$_3$-polymer composite were investigated for dielectric and piezoelectric properties with the barium titanate active particle size. Under the condition of the same density and ceramic volume ratio of composite, the dielectric and piezoelectric constant of composite are increasing as the ceramic particle size in composite are increasing. The surface layer model was quoted to explain these phenomena in our system and experimentally confirmed. The connectivity parameter of modified cube model of composite was calculated from the dielectric constant variation as their particle size. The connectivity parameter X and Y were 77.8% and 98.9% respectively. It means that the barium titanate particle distribution in composite nearly approach to the parallel mode. It was experimentally confirmed that the surface layer has low dielectric and nonferroelectric properties. Dielectric constant and thickness of surface layer were calculated from the equivalent circuit of composite.

• Steel and Composite Structures
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• v.26 no.1
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• pp.1-15
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• 2018

This study reported, the effect of random variation in system properties on bending response of single wall carbon nanotube reinforced composite (SWCNTRC) plates subjected to transverse uniform loading is examined. System parameters such as the SWCNT armchair, material properties, plate thickness and volume fraction of SWCNT are modelled as basic random variables. The basic formulation is based on higher order shear deformation theory to model the system behaviour of the SWCNTRC composite plate. A C0 finite element method in conjunction with the first order perturbation technique procedure developed earlier by the authors for the plate subjected to lateral loading is employed to obtain the mean and variance of the transverse deflection of the plate. The performance of the stochastic SWCNTRC composite model is demonstrated through a comparison of mean transverse central deflection with those results available in the literature and standard deviation of the deflection with an independent First Order perturbation Technique (FOPT), Second Order perturbation Technique (SOPT) and Monte Carlo simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.155-161
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• 2000

In this paper, we studied the relation between heat-treatment temperature of ferrite and electromagnetic wave absorbing properties of ferrite-rubber composite. The heat-treatment temperatures of ferrite are 1200 and $1300^{\circ}C$, 2 hr. As s result. it has been shown that the optimum heat-treatment temperature of ferrite for electromagnetic wave absorber are related to the chemical composition. And, we can control electromagnetic wave absorbing properties of ferrite-rubber composite by the control of heat-treatment temperature of ferrite.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1990.10a
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• pp.86-87
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• 1990

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.512-513
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• 2007

Carbon/polymer based composite electrodes were fabricated by using Super p. Black(SPB) as a conductor and polyvinylidene fluoride (PVDF) as a binder. This type of composite electrode are considered as excellent candidates for heating film and variable resistor applications. Aim of this work is the study of the Mechanical and Electrical properties on composite electrode by the contents of SPB and MWCNT, respectively. The composite electrode having 10~15 wt% of SPB show good electrical and mechanical properties. Mechanical and electrical properties are increased by the addition of MWCNT into the composite electrode.

• Transactions on Electrical and Electronic Materials
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• v.10 no.3
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• pp.97-101
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• 2009

The use of a filler material in epoxy composite materials is an essential condition for reducing the unit cost of production and reinforcing mechanical strength. However, the dielectric strength of insulators decreases rapidly due to interactions between the epoxy resin and filler particles. In contrast to existing composite materials, nano-composite materials have superior dielectric strength, mechanical strength, and enduring chemical properties due to an increase in the bond strength of the polymer and nano material, It is reported that nano-fillers provide new characteristics different from the properties of the polymer material. This study is to improve the insulation capability of epoxy resins used in the insulation of a power transformer apparatus and many electronic devices mold. To accomplish this, the additional amount of nano-$SiO_2$ to epoxy resin was changed and the epoxy/$SiO_2$ nano composite materials were made, and the fundamental electrical properties were investigated using a physical properties and an analysis breakdown test. Using allowable breakdown probability, the optimum breakdown strength for designing an electrical apparatus was determined. The results found that the electrical characteristics of the nano-$SiO_2$ content specimens were superior to the virgin specimens. The 0.4 wt% specimens showed the highest electrical properties among the specimens examined with an allowable breakdown probability of 20 %, which indicates stable breakdown strength in insulating machinery design.