• Structural Engineering and Mechanics
• /
• 제72권2호
• /
• pp.155-168
• /
• 2019

This paper presents the results of an experimental investigation on the compressive strength of small scale concentrically axially loaded fiber-reinforced polymer (FRP) confined plain concrete columns, with cylinder concrete strength 19 MPa. For columns with circular (150-mm diameter) and square (150-mm side) cross sections wrapped with glass- and carbon-FRP sheets (GFRP and CFRP, respectively) applied with dry lay-up the effect of different jacket schemes and different overlap configurations on the confined characteristics is investigated. Test results indicate that the most cost effective jacket configuration among those tested is for one layer of CFRP, for both types of sections. In square sections the location of the lap length, either in the corner or along the side, does not seem to affect the confined performance. Furthermore, in circular sections, the presence of an extra wrap with FRP fibers parallel to the column's axis enhances the concrete strength proportionally to the axial rigidity of the FRP jacket. The recorded strains and the distributions of lateral confining pressures are discussed. Existing design equations are used to assess the lateral confining stresses and the confined concrete strength making use of the measured hoop strains.

• 대한기계학회논문집
• /
• 제16권9호
• /
• pp.1681-1690
• /
• 1992

본 연구에서는 유리섬유강화 플라스틱복합재료를 준비하여 이 재료의 섬유방 향에 따른 파괴인성 및 피로 균열성장거동을 평가하였다.

• Steel and Composite Structures
• /
• 제17권4호
• /
• pp.359-370
• /
• 2014

In this experimental and numerical study, the effect of plate thickness, the diameter of circular cutout, the distance between circular cutouts and rowing orientation angle effect (${\theta}$) on the buckling load of E-glass/vinylester pultruded composite beams with single and double circular cutouts, were investigated. The composite beam having 2, 4, and 6 mm thicknesses was produced as [Mat/${\theta}$ /Mat/${\theta}$ /Mat] by using pultrusion technique. Seven different fiber angles as $0^{\circ}$, $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $75^{\circ}$, and $90^{\circ}$ were chosen for investigation of rowing orientation angle. The distances between each circular cutout were selected as 15, 30, 45, 60, and 75 mm in the case of double circular cutouts. The diameters of circular cutouts were chosen as 2, 4, 6, 8, and 10 mm to investigate the effect of cutout size. The experimental buckling loads were compared with the results calculated from the numerical analysis. ANSYS 11 commercial software was used for numerical study. A good agreement was obtained between numerical and experimental results.

• Structural Engineering and Mechanics
• /
• 제55권1호
• /
• pp.191-204
• /
• 2015

Control of the mechanical behavior of composite materials and structures under monotonic and dynamic loads for cracks and damage is a vast and complex area of research. The modeling of the different physical phenomena and behavior characteristics of a composite material during deformation play an important role in the structural design. Our study aims to analyze numerically the energy release rate parameter G of a composite laminated plate (glass or boron / epoxy) cross-ply [$+{\alpha}$, $-{\alpha}$] in the presence of a crack between two circular notches under the effect of several parameters such as fiber orientation ${\alpha}$, the crack orientation ${\beta}$, the orientation ${\gamma}$ of the two considered circular notches and the effect of mechanical properties. Our results show clearly that both notches orientation has more effect on G than the cracks and fibers orientations.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.1
• /
• pp.429-432
• /
• 2004

The demand for electric power keeps growing, and tends to be more effective. Polymer insulators have been manufactured for almost twenty years and the excellent insulation performance of polymer insulators is attractive. Polymeric materials are now widely used as a replacement for inorganic materials such as porcelain or glass for the outdoor insulation of high voltage insulation. GFRP has been used widely as a core materials for polymer insulators. This paper reports the mechanical properties of GFRP for insulators. The bending strength was simulated and evaluated according to the winding angle. The fiber orientation in GFRP has a great effect on the strength of GFRP because the strength of GFRP mainly depends on the strength of fiber. Results of simulated and evaluated strength of GFRP were compared each other. The simulated strength of GFRP rod was different from the evaluated strength. It was caused that the shear stress had a great effect on the strength of GFRP although the stress of parallel direction of GFRP was much higher.

• 한국전산구조공학회논문집
• /
• 제33권2호
• /
• pp.81-93
• /
• 2020

본 연구를 통해 다양한 분야에서 재료의 역학적 거동을 해석하고 예측하는 방법인 유한요소법(Finite Element Method, FEM)을 활용하여 유리섬유 강화 플라스틱 복합재료의 피로 특성을 분석하였다. 이를 구현하기 위해 평균장 균질화(mean-field homogenization) 이론을 활용하여 고분자, 고무, 금속 등과 같은 다양한 복합재료를 위한 선형, 비선형 다중스케일 재료 모델링 프로그램인 Digimat을 이용하였다. 이를 통해 유리섬유 강화 플라스틱 복합재료의 미세 구조와 재료 모델을 정의하여 더욱 현실적으로 고분자 복합재료의 피로 거동을 예측하고자 한다. 참고문헌을 통해 시험 온도, 섬유배향, 응력비, 시편의 두께 등 다양한 변수들을 사용하여 30wt%의 단 섬유 질량 비율을 갖는 폴리부틸렌 텔레프탈레이트(polybutylene terephthalate, PBT)의 고분자 복합재료의 피로 특성을 조사하였다. 섬유배향 정보를 계산하기 위한 사출해석은 Moldflow 소프트웨어을 활용하였으며, 이를 유한요소 피로시편 모델에 매핑하였다. 대표적인 유한요소 상용 소프트웨어인 LS-DYNA는 섬유배향에 따른 고분자 복합재료의 응력 진폭을 계산하기 위해 Digimat과의 연성해석에 활용하였다. 그리고 수치해석을 활용한 피로수명 해석을 위해 다양한 재료 모델들로 구성된 FEMFAT 소프트웨어를 사용하였다. 선형 재료 모델의 연성해석 결과는 높은 응력 진폭에 의한 재료의 국부적 비선형이 발생하는 LCF 영역의 피로 특성을 연구하기 위해 Neuber 법칙을 사용하여 재료의 피로 거동을 분석하였으며, 비선형 재료 모델의 연성해석 결과 역시 FEMFAT을 활용한 피로수명 해석에 사용되었다. 연성해석과 피로해석의 결과는 섬유배향에 따라 유한요소 시편의 두께 방향으로 분석하여 유리섬유 강화 플라스틱 복합재료의 형태학적, 역학적 구조에 대해서 평가하였다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1995년도 추계학술대회 논문집
• /
• pp.121-124
• /
• 1995

This study is aimed at cutting down the cost, weight and improving process by replacing the traditional sintered piston of the shock absorber with engineering plastic piston by means of injection molding. To obtain the high mechanical properties, glass fiber material was selected adequately and forming analysis considering fiber orientation was made to remove the forming deficit fators and to construct the optimal runner system. In addition, structural analysis using commercial software MOLDFLOW was performed under near conditions in actual driving of automotive. The results from the internal pressure process test, oilproof test based on forming, structural and strength analysis shows that hydraulic close performance and damping force considering the out of roundness of shock absorber are relatively good.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.586-588
• /
• 2001

Inner part of FRP specimen was made unidirectionally by pultrusion method and outer part of FRP was made by filament winding method to study the effect of fiber orientatons on the strength of FRP. The strength of bending and compression was simulated and evaluated. The results of simulated strength and evaluated strength were different greately each other. The stress which affect the feature of FRP was simulated to investigate the difference of the results between simulation and evaluation Shear stresses were investigated to the main stress to affect the fracture of FRP.

• Composites Research
• /
• 제12권1호
• /
• pp.47-58
• /
• 1999

다양한 형상 및 경계조건을 갖는 적층 복합재료 및 혼합적층 복합재료 판의 자유진동해석을 위한 실험적 연구결과에 대하여 고찰하였다. 실험에 사용한 판의 재료는 탄소섬유강화(CFRP), 유리섬유강화(GFRP) 복합재료, 알루미늄-GFRP, CFRP-GFRP 혼합적층 복합재료이다. 충격해머와 가속도계를 이용한 충격가진법을 통하여 판의 고유진동수 및 노달패턴을 얻었고, 결과는 무차원화된 진동수매개변수로 제시하였다. 복합재료의 물성, 적층강도, 판의 기하학적 형상과 경계조건 등이 복합재료 판의 진동특성에 미치는 영향에 대하여 평가하였다. 실험결과의 비교/검증을 위하여 유한요소해석을 수행하였고, 서로 잘 일치함을 보였다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
• /
• pp.234-237
• /
• 2001

In this study, efforts were made to understand the propagation of electromagnetic wave through the foam core sandwich structure by the analytical model. Foam core sandwich structure is composed of glass/epoxy composite skins and foam core. Transmittance and reflectance of the arbitrary linearly polarized incident TEM waves through the unidirectional composites, foam and foam core sandwich structures were determined as functions of thickness, fiber orientation of composites, incident angle and polarization angle by the analytical model. From the results of the analysis, the general tendency of transmittance and reflectance of electromagnetic wave through composites, foam and foam core sandwich structures was obtained.