• Composites Research
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• v.28 no.3
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• pp.104-111
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• 2015

In this work, a structural design on 500W class horizontal axis wind turbine blade using natural-fibre composite is performed. The structural design result of flax composite blade is compared with the result of glass composite blade. The structural design of the wind turbine blade is carried out using the simplified methods such as the netting rule and the rule of mixture. The structural safety of the designed blade structure is investigated through the various load cases, stress, deformation and buckling analyses using the commercial FEM. The structural test of the manufactured prototype blade was performed to confirm the structural analysis results including strains, natural frequencies and deformations. According to the comparison results, it was confirmed that the analysis results are well agreed with the experimental results.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.7-12
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• 2003

When the wind turbine is used in cold regions, the mechanical properties and dimension stability of the blade will be changed. The proposal of this paper is to test the durability of the blade for wind turbine. It is necessary to select the most comfortable materials and fabrication processes for more stable wind turbine blade in cold regions. To select the most comfortable materials and processes, the static strength has to know through the tensile static tests at the severe condition as cold regions. First, the tensile static specimens made by RIM (Resin injection molding) process & vacuum bagging process with reinforcement materials and resin. Tensile static tests were carried out on three laminate lay-ups (carbon prepreg, carbon fiber dry fabric and glass fiber dry fabric) at different test temperature($24^{\circ}$, $-30^{\circ}$), determining properties such as the mechanical strength, stiffness and strain to failure. At different test temperature, in order to test the tensile strengths of these specimens used the low temperature chamber. Next, the results of this test were compared with each other. Finally, the most comfortable materials and fabrication processes can select based on these results. The results show the changes in the static behavior of three laminate lay-ups at different test temperatures. At low temperatures, the static strengths are higher than the ones at room temperature.

• Composites Research
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• v.15 no.1
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• pp.21-31
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• 2002

To overcome the disadvantages of conventional excavation technology various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so far developed have some drawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM (Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

• Composites Research
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• v.27 no.3
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• pp.96-102
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• 2014

In this study, we fabricated jute fiber reinforced polylactic acid (PLA) composite in the form of sandwich panel structure which includes core foam of chopped jute fiber reinforced PLA and outer skin layer of continuous glass fiber reinforced PLA. Flexural properties of the composite were assessed for different jute fiber weight fractions. Density of the core foam ranged from 0.31 to 0.67 $g/cm^3$ and void content fraction 0.51 to 0.71. The maximum flexural strength was 92.7 MPa at 12.5 wt.% of jute fiber content, and the maximum flexural modulus was 7.58 GPa at 30.0 wt.%. Cost analysis was also conducted. The cost to enhance the flexural strength of the applied structure was estimated to be $0.010USD/m^3/MPa$ for 12.5 wt.% fiber content.

• Composites Research
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• v.30 no.1
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• pp.21-25
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• 2017

The aim of this study is to fabricate composite bone plates consisted of unidirectional biodegradable glass fibers (BGF) and polylactic acid (PLA) and evaluate the performance of the composite bone plates according to the temperature ($50.0^{\circ}C$) of PBS (Phosphate Buffer Saline) solution and exposure time (0~3 weeks). Mechanical characteristics, such as bending stiffness, flexural strength, water uptake and mass loss, were investigated and the results showed that mechanical properties of the plates decreased as soaking duration increased due to loss of composite material.

• Composites Research
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• v.14 no.2
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• pp.13-21
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• 2001

Substituting composite structures for conventional metallic structures has many advantages because of higher specific stiffness and specific strength of composite materials. In this work, one-piece driveshafts composed of carbon/epoxy and glass/epoxy composites were designed and manufactured for a rear wheel drive automobile satisfying three design specifications, such as static torque transmission capability, torsional buckling and the fundamental natural bending frequency. Single lap adhesive joint was used to join the composite shaft and the aluminum yoke. The torque transmission capability of the adhesively bonded composite shaft was calculated with respect to bonding length and yoke thickness by finite element analysis and compared with the experimental result. Torque transmission capability was based on the Tsai-Wu failure index fur composite shaft and the failure model which incorporated the nonlinear mechanical behavior of aluminum yoke and epoxy adhesive. From the experiments and the finite element analyses, it was found that the static torque transmission capability of the composite driveshaft was highest at the critical yoke thickness, and saturated beyond the critical length. Also, it was found that the one-piece composite driveshaft had 40% weight saving effect compared with a conventional two-piece steel driveshaft.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.518-525
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• 2009

This paper describes the evaluation of structural performance test and finite element analysis to verify the design of Bimodal Tram made of sandwich composites. The sandwich composite applied to vehicle structure was composed of a aluminum honeycomb core and WR580/NF4000 glass fabric/epoxy laminate composite facesheet. The load tests of vehicle structure were conducted for vertical load, compressive load, torsion and modal analysis according to JlS E 7105. The structural Integrity of vehicle was evaluated by the measurement of displacement, stress and natural frequency obtained from dial gauge, strain gauge and gravity sensor, respectively. And finite element analysis using ANSYS v11.0 was done to compare with structural test. The results showed that the displacement, stress and natural frequency were in an good agreement with those of structural analysis using the proposed finite element models.

• Elastomers and Composites
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• v.44 no.1
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• pp.34-40
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• 2009

New coupling agent or surface modified agent (9-decenoic acid) was used to enhance the compatibility between silica and polystyrene in silica/polystyrene hybrid nanocomposite, synthesized by in situ miniemulsion polymerization. Composites contain well dispersed nanosize silica particles. Related tests and analyses confirmed the success of synthesis. Functionalization of silica by 9-decenoic acid and silica on the polystyrene was confirmed by FTIR. TGA showed presence and amount of silica in final latex. The glass transition temperature of the hybrid nanocomposite was increased with the silica amount. SEM and TEM analysis showed the spherical morphology of PS and composite with an average diameter of 55 nm. The presence of silica within composite was confirmed by EDS attached to the existing TEM.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.137-143
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• 2011

Epoxy resins are widely used as high performance thermosets in many industrial applications, such as coatings, adhesives and composites. Recently, a lot of research has been carried out in order to improve their mechanical properties and thermal stability in various fields. Carbon nanotubes possess high physical and mechanical properties that are considered to be ideal reinforcing materials in composites. CNT-reinforced epoxy system hold the promise of delivering superior composite materials with their high strength, light weight and multi functional features. Therefore, this study used multi-walled carbon nanotubes (MWNT) and gamma rays to improve the mechanical and thermal properties of epoxy. The diglycidyl ether of bisphenol A (DGEBA) as epoxy resins were cured by gamma ray irradiation with well-dispersed MWNTs as a reinforcing agent and triarylsulfonium hexafluoroantimonate (TASHFA) as an initiator. The flexural modulus was measured by UTM (universal testing machine). At this point, the flexural modulus factor exhibits an upper limit at 0.1 wt% MWNT. The thermal properties had improved by increasing the content of MWNT in the result of TGA (thermogravimetric analysis). However, they were decreased with increasing the radiation dose. The change of glass transition temperature by the radiation dose was characterized by DMA (dynamic mechanical analysis).

• Polymer(Korea)
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• v.34 no.4
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• pp.346-351
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• 2010

The mechanical properties of polypropylene (PP) composites, especially the effects of the filler shapes on the modulus were studied. The experimental results were investigated and compared with the theoretical approaches proposed by Lee and Paul and based on Eshelby's principle, which three dimensional ellipsoids were filled as filler and analyzed in terms of aspect ratio, ${\rho}_\alpha=a_1/a_3$ and ${\rho}_\beta=a_1/a_2$. The shapes of fillers were observed by SEM and aspect ratios were statistically calculated. Young's moduli in the longitudinal and transverse directions for barium sulfate whose shape was sphere ($\rho_\alpha=\rho_\beta=1$) had the same values, as predicted values. The modulus in the $x_1$ direction for a glass fibers increased as the filler content increased, while the modulus in the $x_3$ direction was increased relatively small. Furthermore, mica was also used to investigate the effects of the primary and secondary aspect ratios on the mechanical properties.