• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
• /
• pp.813-815
• /
• 1998

In order to analyse the degradation process of epoxy/glass fiber for outdoor condition, FRP laminate was exposed to the wavelength of ultraviolet rays and evaluated by comparing contact angle, surface resistivity, surface potential decay, and ESCA spectrum respectively. Finally, We can conclude that the degradation phenomena on the surface of epoxy composites are dominated by the induction of ester and carboxyl groups.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
• /
• pp.709-714
• /
• 1999

The objectives of this study are to estimate the strengthening effect of concrete column strengthened with CFS and to provide basic guideline for the strengthening design with laminated composite materials. Analysis stress-strain model of laminated CFS is presented based on laminate theory. This model has been implemented in the algorithm of evaluating confinement effect of CFS. From results of the algorithm, stress-strain relationship of confined concrete is obtained. Using this stress-strain relationship, section analyses of circular and rectangular concrete columns strengthened with CFS are carried our, and load-moment interaction and load-ductility curves of the columns are obtained. To evaluate the strengthening effects of CFS, parametric study is also conducted for the angle of ply, thickness of CFS, shape of section, and reinforcement ratio. Based on this investigation, design recommendations and basic guidelines for the strengthening design with CFS are proposed.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.583-586
• /
• 2000

This work ethibits how susceptive the shear ultrasonic waves are to a little misoriented plies according to the angle variation of shear ultrasoic waves $0^\circ$ , $45^\circ$ and $90^\circ$. Also, it is shown that shear waves, particularly the transmission mode with the transmitter and receiver perpendicular to each other, have high sensitivity for detecting anomalies in fiber orientation and ply layup sequence that may occur in the manufacturing of composite laminates. Experimental results are agreed with modeling solutions which were based on decomposition of shear wave polarization vector as it propagates through the composite laminates. This wave appeared considerably to be sensitive to CFRP composites to the thickness direction along in-plane fibers.

• Computational Structural Engineering : An International Journal
• /
• 제1권1호
• /
• pp.39-48
• /
• 2001

An analytical compressive stress-strain relationship model for circular and rectangular concrete specimens confined with laminated carbon fiber sheets (CFS) is studied. Tsai-Hill and Tsai-Wu failure criteria were used to implement orthotropic behavior of laminated composite materials. By using these criteria, an algorithm which analyzes the confinement effect of CFS on concrete was developed. The proposed analytical model was verified through the comparison with experimental data. Various parameters such as concrete strength, ply angle, laminate thickness, section shape, and ply stacking sequences were investigated. Numerical results by the proposed model effectively simulate the experimental compressive stress-strain behavior of CFS confined concrete specimens. Also, the pro-posed model estimates the compressive strength of the specimen to a high degree of accuracy.

• 한국광학회:학술대회논문집
• /
• 한국광학회 2009년도 창립 20주년기념 특별학술발표회
• /
• pp.103-104
• /
• 2009

We proposed the laminate thin film asymmetric Extruded-closed-polygon diffusion pattern that was able to improve the performance of back light unit. Developed a pattern of brightness and bright line, half-power angle attribute the improved performance in the uniform, and through the formation of a thin film stackable diffusion layer 970% improved perpendicularity brightness, and 580% improved horizontality brightness.

• 대한기계학회논문집
• /
• 제19권7호
• /
• pp.1665-1674
• /
• 1995

An optimum design has been performed to maximize specific energy (SED) of composite flywheel rotor for energy storage system. The flywheel rotor is assumed to be an axisymmetric thick laminated shell with a plane strain state for structural analysis. For the structural analysis the centrifugal force is considered and the stiffness matrix equation was derived for each ring considering the interferences between the rings. The global stiffness matrix was derived by integrating the local stiffness matrix satisfying the conditions of force and displacement compatibilities. Displacements are then calculated from the global stiffness matrix and the stresses in each ring are also calculated. 3-D intra-laminar quadratic Tsai-Wu criterion is then used for the strength analysis. An optimum procedure is also developed to find the optimal interferences and lay up angle to maximize SED using the sensitivity analysis.

• Composites Research
• /
• 제30권6호
• /
• pp.410-415
• /
• 2017

본 연구에서는 탄소섬유강화 복합재의 제작 시 열 잔류응력으로 인한 변형을 유한요소 프로그램 ABAQUS에서 User Subroutine을 이용한 유한요소 해석을 통해 예측한다. 탄소섬유강화 복합재의 변형에 영향을 주는 다양한 요인 중 온도구배, 제품 형상, 적층각 및 적층순서, 수지의 화학수축, 열 잔류응력을 고려한 복합재 성형을 해석하였다. 같은 형상의 실제 모델과 해석 모델의 결과를 비교한다. 또한 해석 결과를 분석하여 실제 제작의 오차에 적용하여 실제 제작에서의 성형 완성도를 높이는데 목적이 있다.

• 복합신소재구조학회 논문집
• /
• 제1권4호
• /
• pp.28-34
• /
• 2010

W e performed a geometrical nonlinear dynamic analysis of laminated skew plates made of advanced composite materials (ACM ) based on the first-order shear deformation plate theory (FSDT). The Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of skew angles and layup sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite and skew plates, and the new results reported in this paper show the significant interactions between the skew angle and layup sequence in the skew laminate. Key observation points are discussed and a brief design guideline is given.

• Structural Engineering and Mechanics
• /
• 제43권5호
• /
• pp.657-678
• /
• 2012

The mismatch of ply orientations in composite laminates can cause high interlaminar stress concentrations near the free edges. Evaluation of these interlaminar stresses and their role in the progressive damage analysis of laminates is desirable. Recently, the authors developed a new method to relate the physically based micromechanics approach with the meso-scale CDM considering matrix cracking and induced delamination. In this paper, the developed method is applied for the analysis of edge effects in various angle-ply laminates such as $[10/-10]_{2s}$, $[30/-30]_{2s}$ and $[45/-45]_{2s}$ and comparing the results with available traditional CDM and experimental results. It is shown that the obtained stress-strain behaviors of laminates are in good agreement with the available experimental results and even in better agreement than the traditional CDM results. Variations of the stresses and stiffness components through the laminate thickness and near the free edges are also computed and compared with the available CDM results.

• Structural Engineering and Mechanics
• /
• 제31권5호
• /
• pp.587-603
• /
• 2009

We performed a free vibration analysis of skew composite laminates with or without cutout based on the high-order shear deformation plate theory (HSDT). The effects of skew angles and ply orientations on the natural frequencies for various boundary conditions are studied using a nonlinear high-order finite element program developed for this study. The numerical results are in good agreement with those reported by other investigators for simple test cases, and the new results reported in this paper show the interactions between the skew angle, layup sequence and cutout size on the free vibration of the laminate. The findings highlight the importance of skew angles when analyzing laminated composite skew plates with cutout or without cutout.