• Composites Research
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• v.33 no.4
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• pp.213-219
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• 2020

Recently, global facing environmental issues have been raised caused by plastic waste. Hence, increasing the demand for interest in environmentally friendly materials. In this row, research on engineering composite materials also replacing the synthetic reinforcement by introducing natural fibers. However, focus on the strength and interfacial adhesion between matrix and reinforcement is very essential in natural fiber composite, which is insufficient in the literature. There are number of approaches for improving the mechanical strength of the composites, one of the common methods is to reinforce additive nanoparticles. The present investigation, bio-additives were synthesized utilizing bio-waste, cheap, bio-degradable sea-weed powder that could replace expensive nanomaterials and reinforced into the CFRP composite through Hand lay-up followed by a vacuum process. Mechanical properties were evaluated and analyzed through microanalysis. The results concluded that synthesized additives are effective for improving mechanical properties such as tensile, flexural, impact, and shear strength. Overall, the results confirmed that the fabricated composites have potential applications in the field of engineering applications.

• Geomechanics and Engineering
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• v.21 no.6
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• pp.571-582
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• 2020

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the uniaxial compression tests and numerical studies were carried out. The interaction forms and formation mechanisms at the contact interfaces of different materials were analyzed to reveal the effect of interaction on the mechanical behavior of composite samples. The research demonstrated that there are three types of interactions between the two materials at the contact interface: constraint parallel to the interface, squeezing perpendicular to the interface, and shear stress on the interface. The interaction is mainly affected by the differences in Poisson's ratio and elastic modulus of the two materials, stronger interface adhesion, and larger interface inclination. The interaction weakens the strength and stiffness of the composite sample, and the magnitude of weakening is positively correlated with the degree of difference in the mechanical properties of the materials. The tensile-shear stress derived from the interaction results in the axial tensile fracture perpendicular to the interface and the interfacial shear facture. Tensile cracks in stronger material will propagation into the weaker material through the bonded interface. The larger inclination angle of the interface enhances the effect of composite tensile/shear failure on the overall sample.

• Polymer(Korea)
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• v.33 no.6
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• pp.588-595
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• 2009

The aim of this study was to increase compatibility of immiscible PLA/PCL blend by using electron beam irradiation in the presence of glycidyl methacrylate (GMA). The blends of PLA/PCL containing GMA were irradiated at doses of 10, 50 and 100 kGy and then the irradiated samples were characterized by observing morphology and rheological properties. Blends irradiated with 50 and 100 kGy showed greatly improved interfacial adhesion between two phases in the morphology. Complex viscosity of PLA/PCL(9/1) blend irradiated at dose of 100 kGy was about 100 times higher than that of pure PLA. We found that the compatibility of immiscible PLA/PCL could be improved by electron beam irradiation in the presence of GMA from the investigation of morphology and rheology.

• Polymer(Korea)
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• v.33 no.6
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• pp.530-536
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• 2009

A cycloaliphatic epoxy/acidic anhydride system incorporating short carbon fibers (SCF) and short glass fibers (SGF) was fabricated and thermal/mechanical properties were characterized. At low filler content both SCF- and SGF-reinforced composites showed a similar decrease in coefficient of thermal expansion (CTE), measured by a thermomechanical analyzer, with increasing loadings, above which SCF became more effective than SGF at reducing the CTE. Experimental CTE data for the SCF-reinforced composites is best described by the rule of mixtures at lower SCF contents and by the Craft-Christensen model at higher SCF contents. Storage modulus (E') at $30^{\circ}C$ and $180^{\circ}C$ was greatly enhanced for short fiber-filled composites compared to unfilled specimens, Scanning electron microscopy of the fracture surfaces indicated that the decreased CTE and the increased E' of the short fiber-reinforced composites resulted from good interfacial adhesion between the fibers and epoxy matrix.

• Polymer(Korea)
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• v.28 no.5
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• pp.374-381
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• 2004

Gas permeability of low density polyethylene (LDPE) film containing zeolite powder for $CO_2,\;O_2$ and $N_2$ were investigated. Zeolite powders modified by cations or surfactant were compounded with LDPE to produce $20 wt\%$ masterbatch. After blending the masterbatch with LDPE, zeolite filled films were prepared by the blown film process. Finally, the composite films containing zeolite loadings of 0, 3,5, and $10 wt\%$ were produced. A gas permeability apparatus based on the variable volume principle was designed to analyze the characteristics of films. Experiments showed a general trend that gas permeabilities first decreased and then increased as the zeolite content was increased. Surfactant modified zeolite showed a better interfacial adhesion with the matrix, but the film did not show a discernible difference in gas permeability compared with the other modified films. The difference of temperature dependences in the gas permeabilities of composite films was slightly smaller than that of LDPE film.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.252.2-252.2
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• 2013

ZnO nanostructures have a lot of interest for decades due to its varied applications such as light-emitting devices, power generators, solar cells, and sensing devices etc. To get the high performance of these devices, the factors of nanostructure geometry, spacing, and alignment are important. So, Patterning of vertically- aligned ZnO nanowires are currently attractive. However, many of ZnO nanowire or nanorod fabrication methods are needs high temperature, such vapor phase transport process, metal-organic chemical vapor deposition (MOCVD), metal-organic vapor phase epitaxy, thermal evaporation, pulse laser deposition and thermal chemical vapor deposition. While hydrothermal process has great advantages-low temperature (less than $100^{\circ}C$), simple steps, short time consuming, without catalyst, and relatively ease to control than as mentioned various methods. In this work, we investigate the dependence of ZnO nanowire alignment and morphology on si substrate using of nanosphere template with various precursor concentration and components via hydrothermal process. The brief experimental scheme is as follow. First synthesized ZnO seed solution was spun coated on to cleaned Si substrate, and then annealed $350^{\circ}C$ for 1h in the furnace. Second, 200nm sized close-packed nanospheres were formed on the seed layer-coated substrate by using of gas-liquid-solid interfacial self-assembly method and drying in vaccum desicator for about a day to enhance the adhesion between seed layer and nanospheres. After that, zinc oxide nanowires were synthesized using a low temperature hydrothermal method based on alkali solution. The specimens were immersed upside down in the autoclave bath to prevent some precipitates which formed and covered on the surface. The hydrothermal conditions such as growth temperature, growth time, solution concentration, and additives are variously performed to optimize the morphologies of nanowire. To characterize the crystal structure of seed layer and nanowires, morphology, and optical properties, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) studies were investigated.

• Elastomers and Composites
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• v.49 no.2
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• pp.117-126
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• 2014

Methylene diisocyanate (MDI) was investigated as a novel interfacial modifier to enhance the performances of poly(methyl methacrylate)-modified starch/styrene-butadiene rubber (PMMA-modified starch/SBR) composites. Owing to the formation urethane linkage on one side and ${\pi}-{\pi}$ adhesion on the other side, MDI acted as an intermediated linkage role in the PMMA-modified starch/SBR interfaces, which was evidenced by the morphological, mechanical, dynamic mechanical and thermal decomposition studies. As a result, the presence of MDI significantly improved the mechanical properties and thermal stability of PMMA-modified starch/SBR composites. In addition, the effect of starch concentration on the various performances of the resulted MDI/PMMA-modified starch/SBR composites, such as morphology, vulcanization characteristics, mechanical properties, toluene swelling behavior, and thermal stability were investigated and discussed in detail. The obtained MDI/PMMA-modified starch/SBR composites exhibited superior mechanical properties to carbon black/SBR (CB/SBR) composites, demonstrating the potential use of the renewable starch as a substitute for CB in the rubber compounds.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.198-204
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• 2019

Polymer composites are widely used as industrial materials requiring high mechanical properties. Glass fibers and fillers, which are used as a reinforcement in composites, usually have some problems such as nonuniform dispersion and poor interfacial adhesion. In this study, an acrylic acid-modified polyethylene wax was synthesized by the sequential reaction of pyrolysis of polyethylene followed by grafting with a polar acrylic acid. The acrylic acid-modified polyethylene wax was applied to polymer composites of the polyamide matrix and glass fiber reinforcement. The effect of acrylic acid-modified polyethylene wax on physical properties of polyamide based composites was thoroughly investigated.

• Composites Research
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• v.19 no.4
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• pp.15-22
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• 2006

One of the primary factors limiting the application of composite-metal adhesively bonded joints in structural design is the lack of a good evaluation tool for the interfacial strength to predict the load bearing capacity of boned joints. In this paper composite-steel adhesion strength is evaluated in terms of stress intensity factor and fracture toughness of the interface corner. The load bearing capacity of double lap joints, fabricated by co-cured bonding of composite-steel adherends has been determined using fracture mechanical analysis. Bi-material interface comer stress singularity and its order are presented. Finally stress intensities and fracture toughness of the wedge shape bi-material interface corner are determined. Double lap joint failure locus and its mixed mode crack propagation criterion on $K_1-K_{11}$ plane have been developed by tension tests with different bond lengths.

• Journal of the Korean Wood Science and Technology
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• v.52 no.3
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• pp.205-220
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• 2024

Various polylactic acid (PLA) blends were reinforced with untreated or silane-treated micro-sized cellulose fiber (MCF), successfully prepared as 3D printing filaments and then printed using a fused filament fabrication (FFF) 3D printer. In this study, we focused on developing 3D-printed MCF/PLA composites through silane treatment of MCF and investigating the effect of silane treatment on the various properties of FFF 3D-printed composites. Fourier transform infrared spectra confirmed the increase in hydrophobic properties of silane-treated MCF by showing the new absorption peaks at 1,100 cm^-1, 1,030 cm^-1, and 815 cm^-1 representing C-NH₂, Si-O-Si, and Si-CH₂ bonds, respectively. In scanning electron microscope images of silane-treated MCF filled PLA composites, the improved interfacial adhesion between MCF and PLA matrix was observed. The mechanical properties of the 3D-printed MCF/PLA composites with silane-treated MCF were improved compared to those of the 3D-printed MCF/PLA composites with untreated MCF. In particular, the highest tensile and flexural modulus values were observed for S-MCF10 (5,784.77 MPa) and S-MCF5 (2,441.67 MPa), respectively. The thermal stability of silane-treated MCF was enhanced by delaying the initial thermal decomposition temperature compared to untreated MCF. The thermal decomposition temperature difference at T₉₅ was around 26℃. This study suggests that the effect of silane treatment on the 3D-printed MCF/PLA composites is effective and promising.