• Composites Research
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• v.26 no.4
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• pp.235-244
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• 2013

A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solid containing multiple isotropic elliptical fibers of arbitrary orientation subject to uniform stress at infinity. The fibers are assumed to be long parallel elliptical cylinders composed of isotropic elastic material perfectly bonded to the isotropic matrix. The solid is assumed to be under plane strain on the plane normal to the cylinders. A detailed analysis of the stress field at the matrix-fiber interface for square and hexagonal packing of the fibers is carried out for different values of the number, orientation angles and concentration of the elliptical fibers. The accuracy and efficiency of the method are examined through comparison with results obtained from analytical and finite element methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5A
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• pp.389-397
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• 2011

In this study, an experiment for the biaxial behavior of specimens was carried out to identify whether the isotropic flexure tensile stress of concrete in the BFT method is feasible. Another experiment for the improvement of the BFT method was conducted to ensure the isotropic flexure tensile stress of BFT specimens during the test. In addition, the biaxial flexure strength of concrete given by the improved BFT method was compared to the uniaxial flexure strength by the four-point bending test. Test results show that the isotropic flexure tensile stress of concrete using the BFT method was highly influenced by the surface conditions and warping of the specimens. Using improved BFT method, we could obtained the isotropic flexure tensile stress of concretes. The biaxial flexure strength of BFT was about 32% greater than the uniaxial flexure strength of the four-point bending test. In the experiment, with the smaller scatter, the improved BFT method gave a reliable biaxial flexure strength like the four-point bending test.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.881-889
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• 2010

A volume integral equation method (VIEM) is introduced for solving the elastostatic problems related to an unbounded isotropic elastic solid; this solid is subjected to remote uniaxial tension, and it contains multiple interacting isotropic inclusions. The method is applied to two-dimensional problems involving long parallel cylindrical inclusions. A detailed analysis of the stress field at the interface between the matrix and the central inclusion is carried out; square and hexagonal packing of the inclusions are considered. The effects of the number of isotropic inclusions and different fiber volume fractions on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy and efficiency of the method are clarified by comparing the results obtained by analytical and finite element methods. The VIEM is shown to be very accurate and effective for investigating the local stresses in composites containing isotropic fibers.

• Composites Research
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• v.23 no.4
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• pp.7-13
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• 2010

A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solids containing interacting multiple anisotropic inclusions subject to remote uniaxial tension. The method is applied to two-dimensional problems involving long parallel cylindrical inclusions. A detailed analysis of stress field at the interface between the matrix and the central inclusion is carried out for square and hexagonal packing of the inclusions. Effects of the number of anisotropic inclusions and various fiber volume fractions on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy of the method is validated by solving the single inclusion problem for which solutions are available in the literature.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.59-71
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• 2012

A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in unbounded isotropic elastic solids containing multiple interacting isotropic or anisotropic diamond-shaped inclusions subject to remote uniaxial tension. The method is applied to two-dimensional problems involving long parallel diamond-shaped cylindrical inclusions. A detailed analysis of the stress field at the interface between the matrix and the central inclusion is carried out for square and hexagonal packing of the inclusions. The effects of the number of isotropic or anisotropic diamond-shaped inclusions and of the various fiber volume fractions for the circular inclusions circumscribing its respective diamond-shaped inclusion on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy and efficiency of the method are examined through comparison with results obtained using the finite element method.

• Composites Research
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• v.24 no.6
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• pp.37-48
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• 2011

A volume integral equation method (VIEM) is introduced for the solution of elastostatic problems in an unbounded isotropic elastic solids containing interacting multiple isotropic or anisotropic elliptical inclusions subject to remote uniaxial tension. The method is applied to two-dimensional problems involving long parallel elliptical cylindrical inclusions. A detailed analysis of stress field at the interface between the matrix and the central inclusion is carried out for square and hexagonal packing of the inclusions. Effects of the number of isotropic or anisotropic elliptical inclusions and various fiber volume fractions for the circular inclusion circumscribing its respective elliptical inclusion on the stress field at the interface between the matrix and the central inclusion are also investigated in detail. The accuracy and efficiency of the method are examined through comparison with results obtained from analytical and finite element methods. The method is shown to be very accurate and effective for investigating the local stresses in composites containing isotropic or anisotropic elliptical fibers.

• Computational Structural Engineering
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• v.10 no.1
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• pp.159-171
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• 1997

This study investigates the stress distribution in a transversely isotropic medium containing a spheroidal cavity where the medium is under uniaxial tension in z-direction in one case and pure shear in the plane of isotropy in another case. The technical approach used in this study combines exact analytical and numerical methods. The exact analytical method is based upon three potential functions taken in terms of the Legendre associated functions of the first and second kind. The numerical method is based upon the finite difference approach. Numerical results concerning the two loading conditions with five anisotropic materials are presented.

• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.479-486
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• 2011

In this study, we conducted experiment and finite element analysis on the flexural behavior of the round concrete panels according to the evaluation method of biaxial flexural tensile strengths. The Round Panel Test (RPT) and the Biaxial Flexure Test (BFT) were used to determine the biaxial flexural strength of round plain concrete panels. In order to understand the stress distribution on the panels, we measured load-strain relationship at the center of the panels' bottom surface. Test results show that fracture pattern in RPT and BFT panels are similar, and the tensile stress distribution is uniform in all directions at the center of the bottom surface of the panels for both RPT and BFT. The distribution of stresses in two test specimens coincided with the analysis result. The average biaxial flexural strength of RPT is about 29% greater than those of the BFT. The coefficient of variations (COV) of the RPT and BFT for the biaxial flexure strength is 8%, 6%, respectively, which indicates that BFT method is useful and reliable for determining biaxial flexural strengths of the concrete.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1384-1392
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• 2002

Single fiber pull-out technique has been commonly used to characterize the mechanical behavior of interface in fiber reinforced composite materials. An improved analysis considering the effects of transversely isotropic properties of fiber and the effects of thermal residual stresses in both radial and axial directions along the fiber/matrix interface is developed for the single fiber pull-out test. Although the stress transfer properties across the interface is not much affected by considering the transversely isotropic properties of fiber, interfacial debonding is notably encouraged by the effect. The interfacial shear stress that plays an important role in interfacial debonding is very much affected by the component of axial thermal residual stress in the bonded region, which can induce a two-way debonding mechanism.

• Composites Research
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• v.30 no.3
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• pp.193-201
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• 2017

Molecular dynamics simulation and the Mori-Tanaka micromechanics study are performed to investigate the effect of the covalent grafting between CNT and polyester on the mechanical behavior and load transfer of nanocomposites. The transversely isotropic stress-strain curves are determined through the tension and shear simulations according to the covalent grafting. Also, isotropic properties of randomly dispersed nanocomposites are obtained by orientation averaging the transversely isotropic stiffness matrix. By addressing the grafting, the transverse Young's modulus and shear moduli of the nanocomposites are improved, while the longitudinal Young's modulus decreases due to the degradation of the grafted CNT.