• Composites Research
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• v.29 no.5
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• pp.236-242
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• 2016

In this work, tensile and in-plane shear tests for thermoplastic glass fiber/polypropylene composites were performed at a thermo-forming temperature and their properties were characterized and mathematically expressed by using the non-orthogonal constitutive model. As for the thermo-forming test, half-dome experiments were carried out by varying the usage of a releasing agent and the weight of holders. As results, the optimum final shape having well-aligned symmetry and no wrinkle formation was obtained when the releasing agent was used, and it was found that the careful control of a holding force is crucial to manufacture the healthy product. Furthermore, FEM simulations based on the non-orthogonal model showed similar final shapes and tendency of wrinkle formation with experimental results, and confirmed that wrinkles increase with less holding force and higher punch force is required under high frictional condition.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.4 no.2
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• pp.137-147
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• 1994

This study was designed to identify and quantitate airborne isocyanate simultaneously by HPLC. These samples were collected using 1-(2-pyridyl)piperazine(1-2PP) coated glass fiber filter from polyurethane painting works at 8 wood furniture factories in Kimpo and Inchun. The results obtained were as follows : 1. The most suitable mobile phase condition of simultaneously analyzing isocyanates was 0.01 M ammonium acetate buffer ACN(70/30) adjusted to pH 6.2 from the beginning of the analysis to 20 min and 0.01 M ammonium acetate buffer/ACN(50/50) adjusted to pH 6.2 from 21 min to 40 min using the gradient mode. The peaks of isocyanates were able to obtain within 30 min. 2. The recovery efficiencies for 2,6-TDI, 2,4-TDI, HDI and MDI urea derivates spiked at the target concentration on coated glass fiber tillers were 91.00, 93.42, 91.31 and 94.21 %, respectively. 3. The qualitative analysis of the isocyanates samples from polyurethane spray painting works in wood furnture factories identified Ihree isocyanates, 2,6-TDI, 2,4-TDI and MOI. And their concentration ranges were 0-312.6, 0-56.3 and $0-62.1{\mu}g/m^3$, respectively. A disadvantage of using the colorimetric method for isocyanate analysis is its inability of separating isocyanates. This study identified such three isocyanates as 2,6-TDI, 2,4-TDI and MDI from polyurethane spray painting works in wood furniture factories. These isocyanates were successfully quantitated by HPLC by modifying the mobile phase condition and switching to gradient mode.

• Elastomers and Composites
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• v.46 no.3
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• pp.204-210
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• 2011

In this study, Jute fibers reinforced polypropylene (JFRP) composites were manufactured by injection molding technique. In order to improve the affinity and adhesion between fibers and thermoplastic matrices during manufacturing, Maleic anhydride (MA) as a coupling agent have been employed. Untreated and treated surfaces of jute fibers were characterized using SEM and Fourier transform infrared (FTIR). Physical properties like water absorption rate were studied. Tensile and flexural tests were carried out to evaluate the composite mechanical properties. Tensile test and bending test indicated that JFRP composites show higher strength and modulus than pure PP. In addition, strength and modulus were found to be influenced by the variation of MAPP content (1%, 2%, and 3%). Tensile fracture surfaces were examined using scanning electron microscope. It ensures better interfacial adhesion between fibers and matrix by increasing the percentage of MAPP.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.865-868
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• 2008

As a part of a series of study, this study reviewed the fire proof characteristics of high performance concrete RC column members using non-stripping form that accompanied metal lath lateral confinement to prevent spalling of high performance concrete which is increasingly used recently, and the results are as follows. Flow and air amount both satisfied target range, and compressive strength, over 80MPa at age 28 days, showed high strength range. As for spalling characteristics, in the case of plain in which no fiber is mixed, severe spalling occurred, and in the case of 0.05% nylon("NY" hereinafter)+polypropylene("PP" hereinafter) fiber mixture, only surface area experienced partial spalling. Regarding non-stripping form changes, both non-stripping 25-20 and non-stripping 50-20 experienced spalling at finish material area, and non-stripping 50-20 showed better spalling proof performance than non-stripping 25-20. In the case of non-stripping 50-40, spalling was prevented, and while mass reduction rate was less than 10%, its temperature hysteresis showed the most excellent fire proof performance with base metal surface area maximum temperature $376.1^{\circ}C$.

• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.223-229
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• 2014

In this study, the fire resistance of high strength concrete with organic fibers and polymer powder (PW) was investigated. Two types of the specimens of ${\phi}100{\times}200mm$ and $300{\times}300{\times}600mm$ sizes were prepared. As a result of the test, it was found that the fiber-to-PW mixing ratio of 1:1 achieved the highest fluidity. Further, it was found that the mixing ratios of PP 0.05% + PW 0.05%, PNY 0.05% + PW 0.05% was sufficient to protect the high strength concrete from spalling. For the mock-up specimens of $300{\times}300{\times}600mm$ size, if the required amounts of fibers were added in the concrete. the concrete spalling was resisted. Likewise, in the case of the polymix (PM) together with PW, all the tested specimens were satisfactory for fire resistance performance.

• Advances in nano research
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• v.15 no.4
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• pp.315-328
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• 2023

The main goal of the present study was to assess the effects of eggshell powder (ESP) and halloysite nanotubes (HNTs) on the mechanical properties of abaca fiber (AF)-reinforced natural composites. For this purpose, a limited number of indentation tests were first performed on the AF/polypropylene (PP) composites for different HNT and ESP loadings (0 wt.% ~ 6 wt.%), load amplitudes (150, 200, and 250 N), and two types of indenters (Vickers or conical). The Young's modulus, hardness and plasticity index of each specimen were calculated using the indentation test results and Oliver-Pharr method. The accuracy of the experimental results was confirmed by comparing the values of the Young's modulus obtained from the indentation test with the results of the conventional tensile test. Then, a feed-forward shallow artificial neural network (ANN) with high efficiency was trained based on the obtained experimental data. The trained ANN could properly predict the variations of the mentioned mechanical properties of AF/PP composites incorporated with different HNT and ESP loadings. Furthermore, the trained ANN demonstrated that HNTs increase the elastic modulus and hardness of the composite, while the incorporation of ESP reduces these properties. For instance, the Young's modulus of composites incorporated with 3 wt.% of ESP decreased by 30.7% compared with the pure composite, while increasing the weight fraction of ESP up to 6% decreased the Young's modulus by 34.8%. Moreover, the trained ANN indicated that HNTs have a more significant effect on reducing the plasticity index than ESP.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1416-1422
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• 2001

The objective of this work was to characterize mechanical properties of thermoplastic composites with various forming conditions in compression molding. Randomly oriented long glass fiber reinforced polypropylene(PP) was used in this work. The composite materials contained 20%, 30%, and 40% glass fiber by weight. Compression molding was conducted at various mold temperatures and charge sizes. The temperatures on the mold surface and at the material in the mid-plain were monitored during the molding. Differential Scanning Calorimeter was used to measure crystallinity at both in-side and out-side of the sheet material. Crystallinity at each temperature was also measured by X-ray diffractometer. Dimensional stability was studied at various conditions with the spring forward angle. Among the processing parameters, the crystallization time at the temperature above 130$^{\circ}C$, was found to be the most effective. Spring-forward angle was reduced and the tensile modulus was increased as the mold temperature increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2550-2555
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• 2002

Hybrid composites usually are defined as composites having different types of reinforcements such as fibers and particles. The major advantage of hybrid composites is able to control the material properties such as optical, electrical, and mechanical properties. For this reason, hybrid composites are widely used in automotive, marine, household, and electrical industries. The objective of this work was to investigate processing characteristics in the compression molding of hybrid thermoplastic composites. The mechanical properties of composites manufactured in various forming conditions were monitored. The composites contained randomly oriented long carbon fiber and carbon black in polypropylene(PP) matrix were used. The carbon fiber contents of composites were 5%, 10%, 15%, and 20%, and carbon black contents were 5%, 10%, 15%, 20%, and 25% by weight. Compression molding was conducted at various mold temperatures. Crstallinity was also measured by using X-RD. The tensile modulus of the composites increased with increasing the mold temperature. However, the impact strength of the composites decreased as the mold temperature increased.

• Advances in concrete construction
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• v.8 no.1
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• pp.9-19
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• 2019

This paper describes an experimental investigation on hybrid fiber reinforced concrete (HYFRC) beams. And the main aim of this present paper is to examine the dynamic characteristics and damage evaluation of undamaged and damaged HYFRC beams under free-free constraints. In this experimental work, totally four RC beams were cast and analyzed in order to evaluate the dynamic behavior as well as static load behavior of HYFRCs. Hybrid fiber reinforced concrete beams have been cast by incorporating two different fibers such as steel and polypropylene (PP). Damage of HYFRC beams was obtained by cracking of concrete for one of the beams in each set under four-point bending tests with different percentage variation of damage levels as 50%, 70% and 90% of maximum ultimate load. And the main dynamic characteristics such as damping, fundamental natural frequencies, mode shapes and frequency response function at each and every damage level has been assessed by means of non-destructive technique (NDT) with hammer excitation. The fundamental natural frequency and damping values obtained through dynamic tests for HYFRC beams were compared with control (reference) RC beam at each level of damage which has been acquired through static tests. The static experimental test results emphasize that the HYFRC beam has attained higher ultimate load as compared with control reinforced concrete beam.

• Computers and Concrete
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• v.24 no.1
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• pp.19-35
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• 2019

In this paper, the effect of the type and amount of fibers on the physicomechanical properties of concrete containing fine recycled refractory brick (RRB) and natural aggregate subjected to elevated temperatures was investigated. For this purpose, forta-ferro (FF), polypropylene (PP), and polyvinyl alcohol (PVA) fibers with the volume fractions of 0, 0.25, and 0.5%, as well as steel fibers with the volume fractions of 0, 0.75, and 1.5% were used in the concrete containing RRB fine aggregate replacing natural sand by 0 and 100%. In total, 162 concrete specimens from 18 different mix designs were prepared and tested in the temperature groups of 23, 400, and $800^{\circ}C$. After experiencing heat, the concrete properties including the compressive strength, ultrasonic pulse velocity (UPV), weight loss, and surface appearance were evaluated and compared with the corresponding results of the reference (unheated) specimens. The results show that using RRB fine aggregate replacing natural fine aggregate by 100% led to an increase in the concrete compressive strength in almost all the mixes, and only in the PVA-containing mixes a decrease in strength was observed. Furthermore, UPV values at $800^{\circ}C$ for all the concrete mixes containing RRB fine aggregate were above those of the natural aggregate concrete specimens. Finally, regarding the compressive strength and UPV results, steel fibers demonstrated a better performance relative to other fiber types.