• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.85-88
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• 2002

We have implemented a system of falling weight impact tester. Absorbed energy of orthotropic composites with using T300 fiber, which are composed of the same fiber and stacking number is higher than that of quasi-isotropic specimen over impact energy 7J, but in case of using T700 fiber, much difference does not show. Also, absorbed energy of orthotropic composites with using T300 fiber, which are composed of stacking number and orientation became more than that of T700 fiber specimen; however great change doesn't show in case of quasi-isotropic specimens. Delamination area of impacted specimens was measured with ultrasonic C-scanner to find correlation between impact energy and delamination area. Delamination area and frequency responses was evaluated between impacted and unimpacted specimens. There is a strong correlation between frequency responses and impact-induced delamination. The presence and scale of damages have been investigated based on the variations of frequency responses.

• Steel and Composite Structures
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• v.15 no.1
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• pp.57-79
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• 2013

This paper studies the dynamic instability of laminated composite plates under thermal and arbitrary in-plane periodic loads using first-order shear deformation plate theory. The governing partial differential equations of motion are established by a perturbation technique. Then, the Galerkin method is applied to reduce the partial differential equations to ordinary differential equations. Based on Bolotin's method, the system equations of Mathieu-type are formulated and used to determine dynamic instability regions of laminated plates in the thermal environment. The effects of temperature, layer number, modulus ratio and load parameters on the dynamic instability of laminated plates are investigated. The results reveal that static and dynamic load, layer number, modulus ratio and uniform temperature rise have a significant influence on the thermal dynamic behavior of laminated plates.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2005.11a
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• pp.422-425
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• 2005

In an transversely isotropic composite laminates, the velocities, the particle directions and the amplitudes of reflected and transmitted waves were obtained using the equation of motion, the constitutive equation, and the displacement equation expressed by wave number and frequency Eigenvalue problem involving a velocity was solved by Snell's law. Finally, the results were confirmed by T300 Carbon fiber/5208 Epoxy materials. This approach could be applied to the detection of flaws in a transversely isotropic composite laminates by the water immersion C-scan procedure.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.439-444
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• 2018

This paper presents a numerical study on the behavior of continuous hollow steel beam strengthened using carbon fiber reinforced polymers (CFRP). Most previous studies on the CFRP strengthening of steel beams have been carried out on the steel beams with simple boundary conditions. No independent study, to the researcher's knowledge, has studied on the CFRP strengthening of square hollow section (SHS) continuous steel beam. However, this study explored the effect of the use of adhesively bonded CFRP flexible sheets on the behavior of the continuous SHS steel beams. Finite Element Method (FEM) has been employed for modeling. Eleven specimens, ten of which were strengthened using CFRP sheets, were analyzed under different coverage length, the number of layers, and the location of CFRP composite. ANSYS software was used to analyze the SHS steel beams. The results showed that the coverage length, the number of layers, and the location of CFRP composite are effective in increasing the ultimate load capacity of the continuous SHS steel beams. Application of CFRP composite also caused the ductility increase some strengthened specimens.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.698-707
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• 2003

A new quadratic response surface modeling method is presented. In this method, the incomplete small composite design (ISCD) is newly proposed to .educe the number of experimental runs than that of the SCD. Unlike the SCD, the proposed ISCD always gives a unique design assessed on the number of factors, although it may induce the rank-deficiency in the normal equation. Thus, the singular value decomposition (SVD) is employed to solve the normal equation. Then, the duality theory is used to newly develop the conservative least squares fitting (CONFIT) method. This can directly control the ever- or the under-estimation behavior of the approximate functions. Finally, the performance of CONFIT is numerically shown by comparing its'conservativeness with that of conventional fitting method. Also, optimizing one practical design problem numerically shows the effectiveness of the sequential approximate optimization (SAO) combined with the proposed ISCD and CONFIT.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.10
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• pp.584-592
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• 2003

This paper presents a fuzzy-GA method for the allocation and operation of dispersed generator systems(DGs) based on load model in composite distribution systems. Groups of each individual load model consist of residential, industrial, commercial, official and agricultural load. The problem formulation considers an objective to reduce power loss of distribution systems and the constraints such as the number or total capacity of DGs and the deviation of the bus voltage. The main idea of solving fuzzy goal programming is to transform the original objective function and constraints into the equivalent multi-objectives functions with fuzzy sets to evaluate their imprecise nature for the criterion of power loss minimization, the number or total capacity of DGs and the bus voltage deviation, and then solve the problem using genetic algorithm. The method proposed is applied to IEEE 12 bus and 33 bus test systems to demonstrate its effectiveness. .

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.195-200
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• 2001

Composites have wide applications in aerospace vehicles and automobiles because of the inherent flexibility in their design for improved material properties. Composite tribes 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 fibres, in the matrix and in the fibre-matrix interface in tension, compression and shear. The purpose of this study is to investigate the energy absorption characteristics of CFRP(Carbon Fiber Reinforced Plastics) tubes on static and impact tests. Static compression tests have been carried out using the static testing machine and impact tests have been carried out using the vertical crushing testing machine. Interlaminar number affect the energy absorption capability of CFRP tubes. Also, theoretical and experimental have the same value.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.2
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• pp.62-69
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• 2006

In transversely isotropic composite laminates, the velocities, the particle directions and the amplitudes of reflected and transmitted waves were obtained using the equation of motion, the constitutive equation, and the displacement equation expressed by wave number and frequency. Eigenvalue problem involving a velocity was solved by Snell's law. Finally, the results were confirmed by 7300 Carbon fiber/5208 Epoxy materials. This approach could be applied to the detection of flaws in transversely isotropic composite laminates by the water immersion C-scan procedure.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.106-109
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• 2000

Impact tester was build up to evaluate the characterization of CFRP laminate plates under the low velocity impact. The tests were conducted on several laminates of different ply orientation A system was budded for the impact strength of CFRP laminates in consideration of stress wave propagation theory using drop-weight impact tester as one of impact test. Results indicate that absorbed energy of quasi-isotropic specimen having four interfaces is higher than that of orthotropic laminates with two interfaces. Also the damage area was measured with ultrasonic C-scanner on some samples. In the specimens the relationship was linear between damaged area and absorbed energy to some degree. Absorbed energy in the specimen that ply number, interface number and fiber stacking sequences is same but having hybrid is higher than that of orthotropic laminates without hybrid.

• Communications of Mathematical Education
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• v.11
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• pp.297-305
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• 2001

In this paper, we derive the formula that the number of configuration on the rectangular arrays is counted by the composite shift operator method.