• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.2
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• pp.130-137
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• 2016

Non-destructive testing methods for composite materials (e.g., carbon fiber-reinforced and glass fiber-reinforced plastic) have been widely used to detect damage in the overall industry. This study detects defects using optical infrared thermography. The transient heat transport in a solid body is characterized by two dynamic quantities, namely, thermal diffusivity and thermal effusivity. The first quantity describes the speed with thermal energy diffuses through a material, whereas the second one represents a type of thermal inertia. The defect detection rate is increased by utilizing a lock-in method and performing a comparison of the defect detection rates. The comparison is conducted by dividing the irradiation method into reflection and transmission methods and the irradiation time into 50 mHz and 100 mHz. The experimental results show that detecting defects at 50 mHz is easy using the transmission method. This result implies that low-frequency thermal waves penetrate a material deeper than the high-frequency waves.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1232-1240
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• 2005

The purpose of this paper is that investigates the dynamic behavior characteristic of W.T.S (wind turbine system) and carries out the evaluation analysis during operating W.T.S. To investigate the dynamic behavior characteristic of W.T.S, the experiments to measure vibration of the blade from the attached accelerometer on the flap and edge section of the blade that is one of the most important elements of dynamic characteristic of W.T.S are performed. Natural frequency and mode shape are calculated with commercial program ( ANSYS) using the measured vibration acceleration that receives the signal with F.F.T Analyzer from the accelerometer For validation of these experiments, the finite element analysis is performed with commercial F.E.M program (ANSYS) on the basis of the natural frequency and mode shape. The results indicate that experimental values have good agreements with the finite element analysis.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.283-290
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• 2019

In global competition manufacturing companies have to produce modern, new constructions from advanced materials in order to increase competitiveness. The aim of my research was to develop a new composite cellular plate structure, which can be primarily used for structural elements of road, rail, water and air transport vehicles (e.g. vehicle bodies, ship floors). The new structure is novel and innovative, because all materials of the components of the newly developed structure are composites (laminated Carbon Fiber Reinforced Plastic (CFRP) deck plates with pultruded Glass Fiber Reinforced Plastic (GFRP) stiffeners), furthermore combines the characteristics of sandwich and cellular plate structures. The material of the structure is much more advantageous than traditional steel materials, due mainly to its low density, resulting in weight savings, causing lower fuel consumption and less environmental damage. In the study the optimal construction of a given geometry of a structural element of a road truck trailer body was defined by single- and multi-objective optimization (minimal cost and weight). During the single-objective optimization the Flexible Tolerance Optimization method, while during the multi-objective optimization the Particle Swarm Optimization method were used. Seven design constraints were considered: maximum deflection of the structure, buckling of the composite plates, buckling of the stiffeners, stress in the composite plates, stress in the stiffeners, eigenfrequency of the structure, size constraint for design variables. It was confirmed that the developed structure can be used principally as structural elements of transport vehicles and unit load devices (containers) and can be applied also in building construction.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1345-1350
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• 2014

This paper presented analysis methods for adapting E-glass fiber/epoxy composite (GFRP) materials to an automotive leaf spring. It focused on the static behaviors of the leaf spring due to the material composition and its fiber orientation. The material properties of the GFRP composite were directly measured based on the ASTM standard test. A reverse implementation was performed to obtain the complete set of in-situ fiber and matrix properties from the ply test results. Next, the spring rates of the composite leaf spring were examined according to the variation of material parameters such as the fiber angles and resin contents of the composite material. Finally, progressive failure analysis was conducted to identify the initial failure load by means of an elastic stress analysis and specific damage criteria. As a result, it was found that damage first occurred along the edge of the leaf spring owing to the shear stresses.

• Journal of the Korean Society for Precision Engineering
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• v.26 no.3
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• pp.81-87
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• 2009

Lightweight board has been used for manufacturing various fields of automotive interior trims for years. The GMPU board was constructed with glass fiber mat, honeycomb and polyurethane foamed using polyol and isocyanate materials which were sprayed by robot that is interlocked foaming machine. For more lightweight and cost reduction this paper shows how to optimize GMPU process parameters that related to foaming condition, robot position and robot velocity for polyurethane weight. The results show that flexural strength and modulus of board's specimens were evaluated by robot velocity and moving pattern. Based on that, a innovative process was developed for more lightweight and cost reduction.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.11
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• pp.1604-1611
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• 2003

The experimental investigation of a coal splitter used in the 500㎿(e) boilers of fossil power plant is carried out to validate the design criteria. To predict air flow and the amount of particles at the exit, velocity and the weight of particles are measured on test planes using the coal splitter model with two-dimensional phase doppler particle analyzer and the glass fiber filter. It is found that the position of guide plate influences significantly both flow rates of gas and particle at the exit. Gas flow rate was a linear function of the guide plate, whereas particle flow rate was a exponential function of it.

• 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.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.813-815
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• 1998

In order to analyse the degradation process of epoxy/glass fiber for outdoor condition, FRP laminate was exposed to the wavelength of ultraviolet rays and evaluated by comparing contact angle, surface resistivity, surface potential decay, and ESCA spectrum respectively. Finally, We can conclude that the degradation phenomena on the surface of epoxy composites are dominated by the induction of ester and carboxyl groups.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1231-1235
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• 2010

The tensile failure behavior of polymer matrix composite materials was investigated with the aid of a nondestructive evaluation (NDE) technique. The materials, E-glass fiber reinforced epoxy matrix composites, which are applicable to carbody materials in railway vehicles to reduce weight, were used for this investigation. In order to explain stress-strain behavior of polymer matrix composite sample, the infrared thermography technique was employed. A high-speed infrared (IR) camera was used for in-situ monitoring of progressive damages of polymer matrix composite samples during tensile testing. In this investigation, the IR thermography technique was used to facilitate a better understanding of damage evolution, fracture mechanism, and failure mode of polymer matrix composite materials during monotonic loadings.

• Journal of Korean Society for Atmospheric Environment
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• v.10 no.E
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• pp.325-331
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• 1994

Organic extracts of diesel- exhaust particulates were analyzed for mutagenicity using Ames Salmonella typhimurium assay system. An experimental diesel microbus used was drived on the chassis dynamometer according to CVS-75 mode. The samples were taken from the mixed gases in a dilution tunnel. With a high-volume air sampler equipped with double filter holders, particulate matters were collected on a teflon-coated glass fiber filter placed behind a activated carbon filter. After ultrasonic extraction with benzene- ethanol and evaporation to dryness, the residue was dissolved in dimethylsulfoxide. Each sample was tested toward 2 strains, TA100 and TA98 by the pre-incubation method in the absence and presence of S-9mix. Average concentration of diesel- exhaust particulates was about 116.6mg/m$^3$, and 44.1~62.2 ％ to the total weight of particulates, consisted of organic matters. The mutagenicities of diesel- exhaust particulate organic matters were 4,512 and 2,205 revertants/m$^3$ toward TA100 without and with S-9mix, respectively. Those toward TA98 were 13,367 and 3,715 revertants/m$^3$, respectively.