• Composites Research
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• v.23 no.6
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• pp.26-31
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• 2010

This research work contributes to a study for the procedure and methodology to assess the fatigue durability for a composite torque link for helicopter landing gear, which was newly developed and fabricated by the resin transfer moulding technique to interchange with metal component. The simulated load spectrum anticipated to be applied to the torque link during its operation life was generated using an advanced method of probabilistic random process, and the fatigue durability was evaluated by the residual strength degradation approach on the basis of material test data. The full scale fatigue test was performed and compared with the analysis results.

• Composites Research
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• v.23 no.6
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• pp.47-54
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• 2010

Thermal vibration characteristics of a thin walled composite beam attached on spacecraft are investigated in this paper. The composite beam is assumed to have a thin CUS(circumferentially uniform stiffness) wall and modeled with several composite materials which are already space qualified such as T300/Epoxy, YS90AEpoxy. Steady state angle and peak to peak error in spacecraft attitude angle and tip displacement of composite beams are evaluated as a performance index for thermal vibration characteristics. Evaluation results shows that composite beam made out of YS90A has nearly 2 times better than T300 in terms of peak to peak attitude error angle.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.191-204
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• 2015

Control of the mechanical behavior of composite materials and structures under monotonic and dynamic loads for cracks and damage is a vast and complex area of research. The modeling of the different physical phenomena and behavior characteristics of a composite material during deformation play an important role in the structural design. Our study aims to analyze numerically the energy release rate parameter G of a composite laminated plate (glass or boron / epoxy) cross-ply [$+{\alpha}$, $-{\alpha}$] in the presence of a crack between two circular notches under the effect of several parameters such as fiber orientation ${\alpha}$, the crack orientation ${\beta}$, the orientation ${\gamma}$ of the two considered circular notches and the effect of mechanical properties. Our results show clearly that both notches orientation has more effect on G than the cracks and fibers orientations.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.205-211
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• 2007

In this paper, foam-composite sandwich structures for EDM machine tool components such as column and column block designed by controlling stacking sequences and cross-sectional dimensions of the composite structures. The original column block is a box-shaped structure made of aluminum connecting a column and a Z-stage of the system. This research was focused on the design of efficient column block structure using a foam-composite sandwich structure which have good bending stiffness and damping characteristics to reduce the mass and increase damping ratio of the system. Vibration tests for getting damping ratio with respect to the stacking angle and thickness of the composites were carried out. Finite element analyses for static defection and vibration behaviour were also carried out to find out the appropriate stacking conditions; that is, stacking sequence and rib configuration. From the test and analysis results it was found that composite-foam sandwich structures for the microfactory system can be successful alternatives for high precision machining.

• Journal of the Korea Safety Management & Science
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• v.4 no.2
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• pp.189-197
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• 2002

Composites have wide applications in aerospace vehicles and automobiles because of the inherent flexibility in their design lot improved material properties. Composite tubes in particular, are potential candidates for their use as energy absorbing elements in crashworthiness applications due to their high specific energy absorbing capacity and the stroke efficiency. Their failure mechanism however is highly complicated and rather difficult to analyze. This includes fracture in fibers, in the matrix and in the fiber-matrix interface in tension, compression and shear. The purpose of this study is to investigate the energy absorption characteristics of Gr/E(Graphite/Epoxy) tubes on static and impact tests. The collapse characteristics and energy absorption of a variety of tubes have been examined. Changes in the lay-up which increased the modulus increased the energy absorption of the tubes. Based on the test results, the following remarks can be made: Among CA15, CA00 and CA90 curves the CA90 tube exhibits the highest crush load throughout the whole crush process, and max load increases as interlaminar number increase. Among all the tubes type CC90 has the largest specific crushing stress of 52.60 kJ/kg which is much larger than other tubes.

• Elastomers and Composites
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• v.34 no.1
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• pp.31-44
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• 1999

Interfacial adhesive strength between the fully-crosslinked and partially-crosslinked rubber layers were Investigated at the temperature range of $30{\sim}120^{\circ}C$ for four different rubbers(NR, SBR, EPDM, BIMS). The surfaces of interfacial failure were also investigated using a scanning electron microscopy(SEM). The physical interlinking played a major role in the adhesive strength between the fully-crosslinked rubber layers. When a partially-crosslinked rubber layer was bonded to the fully-crosslinked one, the chemical as well as the physical interlinking affected the adhesive strength. NR showed a "interfacial knotty tearing" pattern, while EPDM showed a typical "cross-hatched" one when the adhesive strength approached to the cohesive tear strength of each material.

• Elastomers and Composites
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• v.46 no.1
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• pp.2-9
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• 2011

Permeability to gases and vapors is an important function in tires, rubber tubes and diaphragms. It mainly depends on the rubber material. Generally, permeability increases in the following order: silicone rubber > NR > EPDM > SBR > NBR > FPM > ECO > IIR. And, for an elastomer permeability is also very much dependent on compounding. Many research works are reported in the area of gas permeability for formed rubber,$^{1-7}$ however, few studies are found for unformed elastomer products. Incorporation of nano-particles, use of thermoplastic elastomers and applying high barrier multilayer coatings are the main approaches to obtain a high barrier elastomeric product. In this paper, barrier article for vehicle is introduced.

• Elastomers and Composites
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• v.47 no.2
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• pp.96-103
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• 2012

This paper reviews recent technologies for recycling poly (ethylene terephthalate) wastes. Wide application and non-biodegradability of the PET creates huge amounts of waste and disposal, leading to an environmental problem and economic loss. Chemical recycling can be a promising technology to deal with these problems by converting the waste into useful feedstock material for polyester production. Chemical recycling of polyethylene terephthalate are processes where the PET polymer chain is destructed by the impact of glycol (MEG) causing glycolysis, methanol causing methanolysis or water causing hydrolysis. After intensive purification polyester oligomers or the monomers MEG, dimethyl telephthalate (DMT) or purified terephthalic acid (PTA) are received which are re-used to produce polyester products.

• Elastomers and Composites
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• v.53 no.3
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• pp.109-123
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• 2018

The effect of the silica content on the state and properties of silica-filled styrene-butadiene rubber/butadiene rubber (SBR/BR) compounds containing coupling and dispersion agents was evaluated by varying the content of silica from 50 to 120 phr. Bis-[(triethoxysilyl)propyl] tetrasulfide (TESPT) and zinc 2-ethylhexanoate (ZEH) were used as the coupling and dispersion agents, respectively. The maximum silica content in the pristine material was 80 phr, which increased to 120 phr upon the addition of TESPT and ZEH. The incorporation of TESPT considerably improved most of the rubber properties due to its coupling action and the suppression of silica flocculation, while further addition of ZEH resulted in additional improvements. The properties of the rubber compounds with different silica contents can be fully explained either by an enhancement of the rubber-silica interactions or by their deterioration due to an excessive amount of silica aggregates.

• Structural Engineering and Mechanics
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• v.23 no.2
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• pp.147-161
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• 2006

Recent developments in fractal theory suggest that fractal may provide a more realistic representation of characteristics of cementitious materials. In this paper, the roughness of fracture surfaces in cementitious material has been characterized by fractal theory. A systematic experimental investigation was carried out to examine the dependency of fracture parameters on the aggregate sizes as well as the loading rates. Three maximum aggregate sizes (4.76 mm, 12.7 mm, and 19.1 mm) and two loading rates (slow and fast loading rate) were used. A total of 25 compression tests and 25 tension tests were performed. All fracture parameters exhibited an increase, to varying degrees, when aggregates were added to the mortar matrix. The fracture surfaces of the specimens were digitized and analyzed. Results of the fractal analysis suggested that concrete fracture surfaces exhibit fractal characteristics, and the fractal geometry provide a useful tool for characterizing nonlinear fracture behavior of concrete. Fractal dimension D was monotonically increased as maximum aggregate sizes increase. A new fractal fracture model was developed which considers the size and shape of aggregate, and the crack paths in the constituent phases. Detailed analyses were given for four different types of fracture paths. The fractal fracture model can estimate fractal dimension for multiphase composites.