• Composites Research
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• v.31 no.4
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• pp.156-160
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• 2018

In this paper, evaluation method of structural integrity for cone-type composite lattice structures with hexagonal cell was conducted. A finite element analysis was used to evaluate the structural integrity of cone-type composite lattice structure. The finite element model for evaluation of structural integrity was generated using solid element. In order to consider the difference in mechanical properties between intersection and non-intersection part, the mechanical properties were applied considering the fiber volume fraction of each part. Compression test of cone-type composite lattice structure were conducted for verification of evaluation method of structural integrity. The analysis result showed 2% errors in displacement and good agreement with test result.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.8
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• pp.849-855
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• 2014

The GFRP composite is used for hot press flow molding of automotive components, and the different flow rates of fiber and plastic are likely to induce fiber orientation and inhomogeneity in the material. However, very limited systematic research studies are available on composite materials with superior flow homogeneity and optimized fiber orientation. The inhomogeneity and fiber orientation issues of GFRP composites have still not been resolved through research. The plain weaving method applied to the GFRP prepreg can improve its recyclability, inhomogeneity, fiber flow, structural stability, fiber deformation, surface smoothness, degree of impregnation, and other mechanical properties. The need for more detailed and thorough studies is evidenced.

• Structural Engineering and Mechanics
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• v.65 no.2
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• pp.163-171
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• 2018

Plain concrete is a brittle material with a very low tensile strength compared to compressive strength and critical tensile strain. This study analyzed the dynamic characteristics of high-performance fiber-reinforced cementitious composites based on slurry-infiltrated fiber concrete (SIFCON-based HPFRCC), which maximizes the steel-fiber volume fraction and uses high-strength mortar to increase resistance to loads, such as explosion and impact, with a very short acting time. For major experimental variables, three levels of fiber aspect ratio and five levels of fiber volume fraction between 6.0% and 8.0% were considered, and the flexural strength and toughness characteristics were analyzed according to these variables. Furthermore, three levels of the aspect ratio of used steel fibers were considered. The highest flexural strength of 65.0 MPa was shown at the fiber aspect ratio of 80 and the fiber volume fraction of 7.0%, and the flexural strength and toughness increased proportionally to the fiber volume fraction. The test results according to fiber aspect ratio and fiber volume fraction revealed that after the initial crack, the load of the SIFCON-based HPFRCC continuously increased because of the high fiber volume fraction. In addition, sufficient residual strength was achieved after the maximum strength; this achievement will bring about positive effects on the brittle fracture of structures when an unexpected load, such as explosion or impact, is applied.

• Membrane Journal
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• v.16 no.2
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• pp.85-105
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• 2006

Poly(lactic acid) is a linear aliphatic thermoplastic polyester, produced by the ring-opening polymerization of lactides and the lactic acid monomers, which are obtained from the fermentation of sugar feed stocks, corn, etc. PLA has high mechanical, thermal plasticity, fabric-ability, and biocompatibility, So PLA is a promising polymer far various end-use applications. In recent time, the intercalation of polymers from either solution or the melt in the silicate galleries of clay is the best technique to prepare nanocompoiste material which often exhibit remarkable improvement of mechanical, thermal, optical and physicochemical properties when compared with the pure polymer or conventional composites. Layered silicate is naturally abundant, economic, and more importantly benign to the environment.

• Composites Research
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• v.17 no.3
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• pp.15-22
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• 2004

Acoustic load generated by rocket propulsion system is one of major dynamic loads during lift-off phase so that it causes the structural failure and electronic malfunction of payloads. Acoustic loads can be greatly reduced by an appropriate acoustical design of nose faring structures. This paper deals with the acoustical design of the nose fairing structure for launch vehicle. It is well known that a honeycomb sandwich structure is a poor sound insulator because of its high specific stiffness. In this paper, the sound transmission characteristics of four kinds of honeycomb structures for noise fairing were investigated by means of numerical and experimental ways. In order to estimate transmission loss, infinite plate theory by Moore and Lyon and statistical energy analysis (SEA) method were used. The predicted results showed a good agreement with measured ones. These enabled us to determine a proper core material for nose fairing, which shows good sound insulation performance per weight.

• Composites Research
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• v.17 no.3
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• pp.45-50
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• 2004

The dynamic properties of short-fiber reinforced chloroprene rubber with different interphase conditions and fiber contents have been studied as functions of frequency, amplitude and temperature. The loss factor(LF) slightly increased more than 1.33% of strain and the dynamic ratio(DR) rapidly decreased with increasing strain amplitude. The LF rapidly decreased with increasing frequency especially more than 50Hz. The DR showed the lower when it compared to virgin material with increasing frequency. The LF showed the maximum at $65^{\circ}$ and rapidly decreased after that temperature. The DR showed the lower when it compared with virgin rubber with increasing temperature. Generally, the better interphase condition showed the lower LF and DR at the same testing condition. Therefore, the short-fiber reinforced rubber could have the better isolation when the frequency ratio is more than $\sqrt{2}$ compared with frequency ratio less than $\sqrt{2}$.

• Composites Research
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• v.17 no.5
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• pp.54-60
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• 2004

A new three-dimensional model for predicting the relationship between the prestrain of the composite and the amount of phase transformation of shape memory alloy inducing shape memory effect has been proposed by using Eshelby's equivalent inclusion method with Mori-Tanaka's mean field theory. The model composite is aluminum matrix reinforced with short TiNi fiber shape memory alloy, where the matrix is work-hardening material of power-law type. The analytical results predicted by the current model show that most of the prestrain is induced by the plastic deformation of the matrix, except the small prestrain region. The strengthening mechanism of the composite by the shape memory effect should be explained by excluding its increase of yield stress due to the work-hardening effect of the matrix.

• Composites Research
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• v.12 no.5
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• pp.98-109
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• 1999

An investigation has been performed to develop a nonlinear finire element method for the analysis of the long-term behavior of an artificial hip joint. The three dimensional multi-layered brick element is used to analyze the design performances of hip prodtheses with various materials and the thick laminated composite hip prostheses with various layup sequences. The used element can accommodate the varying material properties of the element and allow the ply-drop-off along the eleement edge. The nonlinear finite element analysis program has been verified by the comparison with the exact solution of the bean problem subjected to uniaxial loading. By using the program, the density changes and strength ratios of artificial hip joint are calculated according to the hip prosthesis materials and the layers of composite hip prosthesis. The numerical results are easily applied to evaluate design performances of a hip prosthesis, and decrease the difficulty and time of hip prosthesis design.

• Composites Research
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• v.17 no.3
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• pp.29-37
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• 2004

The aeroelastic stability analysis of composite bearingless rotors is investigated using a large deflection beam theory in hover. The bearingless rotor configuration consists of a single flexbeam with a wrap-around type torque tube and the pitch links located at the leading edge and trailing edge of the torque tube. The outboard main blade, flexbeam and torque tube are all assumed to be an elastic beam undergoing flap bending, lead-lag bending, elastic twist and axial deflections, which are discretized into beam finite elements. For the analysis of composite bearingless rotors, flexbeam is assumed to be a rectangular section made of laminate. Two-dimensional quasi-steady strip theory is used for aerodynamic computation. The finite element equations of motion for beams are obtained from Hamilton's principle. The p-k method is used to determine aeroelastic stability boundary. Numerical results are presented for selected bearingless rotor configurations based on the lay-up of laminae in the flexbeam and pitch links location. A systematic study is made to identify the importance of the stiffness coupling terms on aeroelastic stability for various fiber orientation and for different configuration.

• Composites Research
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• v.25 no.4
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• pp.126-132
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• 2012

It is useful to have a quick analysis program in early design process for feasibility studies of composite cylinder because it takes long time and is not cost effective by commercial programs. In this paper, a GUI program is developed to calculate the stress distribution in a fast manner with the properties, the orientation angle and the stacking sequence of composite material using LabVIEW. The stress distributions of an autofrettaged cylinder and a composite cylinder with internal pressure are compared with the results by MSC Nastran/patran. The stress distribution of steel/composite cylinder is compared with the values of existing studies, and is proved. Furthermore, by calculating the stress distribution of an autofrettaged steel/composite cylinder, the stress distribution is estimated, and the program will be useful in an early design phase for feasibility studies.