• Composites Research
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• v.14 no.6
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• pp.38-46
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• 2001

In this study, An optimization code that can design microwave absorbing composite laminates is developed, and 3-layered microwave absorbing composite laminates are developed by optimizing the thickness of each layer. The layers are 3 different composite laminates. Many variables including lay-up angles of electromagnetically orthotropic composite layer can be considered in this code. The developed laminate is composed of an impedance matching layer of glass/epoxy fabric laminate, a glass/epoxy fabric laminate layer containing aluminum filler and carbon/epoxy fabric laminate layer. Permittivities of the materials are obtained using a network analyzer and a coaxial air line.

• Composites Research
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• v.33 no.3
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• pp.115-124
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• 2020

Laminate composites, especially Carbon fiber-reinforced composites are wide used in various industry such as aerospace and automotive industry due to their high specific strength and specific stiffness. However, the laminate composites has a big disadvantage that delamination occurs because the arrangement of the fibers is all arranged in the in-plane direction, which limits the field of application of the laminate composites. In this study, we first developed a laminate composites T-beam in which π-beam and flat plate were combined and optimized the design parameters through structural analysis and mechanical tests. Afterwards, 3D weave preform T-beam was developed by applying the same design parameters of laminate composites T-beams, and improved mechanical strength was achieved compared to laminated structures. These findings are expected to be applicable to existing laminated composite structures that require increased strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.3
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• pp.123-131
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• 2007

The buckling behavior of a fiber reinforced plastic pipe was researched. When a cylindrical structure is made of isotropic material, it shows two dimensional buckled shape which has same deformed section along the longitudinal direction. But an anisotropic cylindrical structure shows three dimensional buckled shape which has different deformed section along the longitudinal direction. Because the modulus of elasticity is varied in a certain direction when ply angles are changed, the strength of a pipe are changed as ply angles are changed. In this study, the limitation of two dimensional and three dimensional buckling mode was investigated and the buckling strength of a laminated composite pipe was evaluated.

• Composites Research
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• v.14 no.3
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• pp.1-9
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• 2001

A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue life of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the 90-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminates. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on $[{90}_2/0_2]_s$ carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2001.11a
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• pp.349.2-363
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• 2001

안전성의 측면에서 기계설비 및 구조물의 파손을 유발할 수 있는 재료손상에 대한 평가는 매우 중요하기 때문에, 사용 목적에 부합되는 우수한 첨단재료의 개발과 그 특성을 파악할 필요성이 있다 그 중에서 섬유강화 복합재료는 금속재료보다 높은 비강도와 비강성을 가지며 적층각도, 적층순서 및 경화방법에 따라서 원하는 강도와 강성을 가질 수 있다 특히, 탄소섬유강화복합재료(CFRP)는 스포츠용품에서 최신 항공기의 구조재료에 이르기까지 경량화 관점에서 기존의 재료를 대체해 나가고 있다.(중략)

• Composites Research
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• v.36 no.1
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• pp.48-52
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• 2023

Fiber-reinforced composites have anisotropic material properties, so the mechanical properties of composite structures can vary depending on the stacking sequence. Therefore, it is essential to design the proper stacking sequence of composite structures according to the functional requirements. However, depending on the manufacturing condition or the shape of the structure, there are many cases where the designed stacking angle is out of range, which can affect structural performance. Accordingly, it is important to analyze the stacking angle in order to confirm that the composite structure is correctly fabricated as designed. In this study, the stacking angle was predicted from real cross-sectional images of fiber-reinforced composites using convolutional neural network (CNN)-based deep learning. Carbon fiber-reinforced composite specimens with several stacking angles were fabricated and their cross-sections were photographed on a micro-scale using an optical microscope. The training was performed for a CNN-based deep learning model using the cross-sectional image data of the composite specimens. As a result, the stacking angle can be predicted from the actual cross-sectional image of the fiber-reinforced composite with high accuracy.

• Composites Research
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• v.13 no.2
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• pp.8-21
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• 2000

In th is paper. the low degree of homogeneity issue in the effective modulus was studied for plain weave textile composites. Unit cell analyses were performed using multi-field macroelements. The effective moduli were calculated for finite and infinite configurations and the statistics assessment of the results was presented. Results indicated that the effective modulus of plain weave textile composites depended strongly on the fiber tow phase shift angles and the number of layers. As the number of layers increased, however, the distribution of the modulus showed concentration and higher degrees of homogeneity was attained.

• Journal of Sensor Science and Technology
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• v.8 no.6
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• pp.440-447
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• 1999

Tensile stress loaded on smart composite structures and thermal stress occurred during the during process of the smart composite materials with embedded optical fiber sensors affect directly the mechanical behavior of the embedded optical fiber sensors within the smart composite structures. Stress distribution within the optical fiber sensors varies with respect to the stacking sequence of the composite laminate and the coating conditions of the optical fibers. The cracks occurred within the composite laminate affect not only the fracture of the composite laminate but also the fracture of the optical fiber sensors embedded within the composite laminate. In this study, firstly, stress distribution of the optical fiber sensors embedded within the composite laminate which is subjected to the tensile and thermal stresses was analyzed using Finite Element Method. And, secondly, the effect of the stacking sequence of the composite laminate and the coating conditions of the optical fiber sensors on the stress distribution of the optical fiber sensors was investigated. Finally, the effect of the crack occurred within the smart composite laminate on the fracture behavior of the optical fiber sensors was also observed through the tensile test.

• Composites Research
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• v.19 no.3
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• pp.29-36
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• 2006

Since composite materials have anisotropic properties that depend on their stacking angle and sequence, the analysis of joints with isotropic adherends is limited in describing the behavior of the adhesive Joint with composite adherends. In this study, the nonlinear solution for adhesive joints with composite adherends was derived by incorporating the nonlinear behavior of the adhesive into the analysis. The behavior of the laminated composite tube was first analyzed, and the stress distributions of the composite tubular adhesive joint were calculated by including the nonlinear properties of the adhesive. The effect of the stacking sequence of composite adherends and bonding length on torque capacities of joints was examined, and results of the nonlinear analysis were also compared with those of the linear analysis.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.05a
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• pp.15.2-15.2
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• 2007