• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.49-52
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• 2000

A new composite manufacturing technique which combines winding and curing together is studied and analyzed. This method is especially suited to the manufacture of thick composite materials in which thermal spiking is a common problem. An experimental apparatus was designed and built for use with a filament winder to continuously cure a thick composite cylinder. A hoop-wound composite cylinder with 152 mm wall thickness was manufactured and embedded thermocouples and strain gages were monitored throughout the cure process. The experimental data were compared with analytical results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.245-248
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• 2005

During manufacturing thick composite cylinders, large thermal residual stresses are developed and induce catastrophic interlaminar failures. Since the residual stresses are dependent on many process parameters, such as temperature distribution during cure, cure shrinkage, winding tension, and migration of fibers, calculation of the residual stresses is very difficult. Therefore a radial-cut method have been used to measure the residual stresses in the composite cylinders. But the conventional radial-cut method needs to know numerous material properties which are not only troublesome to obtain but also vary with change of fiber arrangement during consolidation. In this paper, a new radial-cut method with cut-cylinder-bending test was proposed and the measured residual stresses were compared with calculated thermal residual stresses. It was found that the new radial-cut method which does not need to know any of material properties gave better estimation of residual stresses regardless of radial variation of material properties. Additionally, interlaminar tensile strength could be obtained by the cut-cylinder-bending test.

• Composites Research
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• 제24권2호
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• pp.22-29
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• 2011

높은 내압을 받는 장축후육실린더의 성능향상을 위해 최근 그 길이가 길어짐에 따라 무게 또한 무시할 수 없는 변수로 떠오르게 되었다. 따라서 본 논문은 이러한 현상에 대처하기위한 대안으로 장축후육실린더의 무게를 줄이고 대신 복합재 테이프를 감아 무게감소와 더불어 벤딩 (bending)현상을 줄이기 위한 목적으로 복합재가 AISI4340 후육실린더에 미치는 영향을 살펴보았다. 우선 크기가 감소된 AISI4340 후육실린더에 높은 내압을 받는 압력용기 등에 주로 사용되는 자긴가공(autofrettage) 공법을 모사한 후 T300/S208, IM7/PETI5, IM7/8552 테이프를 적용하여 각각의 복합재가 AISI4340 후육실린더에 감을 때 발생되는 응력분포를 살펴봄으로써 탄성계수 및 적층각에 따른 영향을 고찰하였다. 또한 복합재IAISI4340 이중구조 후육실린더의 적층각 도출을 위한 다양한 적층각 조합용 통해 적층각 도출을 위한 전초를 마련하였다. 본 논문을 위한 해석에는 MSC.Nastran/Patran v.2005가 사용되었다.

• Steel and Composite Structures
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• 제51권2호
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• pp.139-151
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• 2024

In this research, a semi-analytical solution is presented for computing mechanical displacements and thermal stresses in rotating thick cylindrical pressure vessels made of functionally graded material (FGM). The modulus of elasticity, linear thermal expansion coefficient, and density of the cylinder are assumed to change along the axial direction as a power-law function. It is also assumed that Poisson's ratio and thermal conductivity are constant. This cylinder was subjected to non-uniform internal pressure and thermal loading. Thermal loading varies in two directions. The governing equations are derived by the first-order shear deformation theory (FSDT). Using the multilayer method, a functionally graded (FG) cylinder with variable thickness is divided into n homogenous disks, and n sets of differential equations are obtained. Applying the boundary conditions and continuity conditions between the layers, the solution of this set of equations is obtained. To the best of the researchers' knowledge, in the literature, there is no study carried out bi-directional thermoelastic analysis of clamped-clamped rotating FGM thick-walled cylindrical pressure vessels under variable pressure in the longitudinal direction.

• Steel and Composite Structures
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• 제27권3호
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• pp.255-271
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• 2018

This paper deals with the transient dynamic analysis and elastic wave propagation in a functionally graded graphene platelets (FGGPLs)-reinforced composite thick hollow cylinder, which is subjected to shock loading. A micromechanical model based on the Halpin-Tsai model and rule of mixture is modified for nonlinear functionally graded distributions of graphene platelets (GPLs) in polymer matrix of composites. The governing equations are derived for an axisymmetric FGGPLs-reinforced composite cylinder with a finite length and then solved using a hybrid meshless method based on the generalized finite difference (GFD) and Newmark finite difference methods. A numerical time discretization is performed for the dynamic problem using the Newmark method. The dynamic behaviors of the displacements and stresses are obtained and discussed in detail using the modified micromechanical model and meshless GFD method. The effects of the reinforcement of the composite cylinder by GPLs on the elastic wave propagations in both displacement and stress fields are obtained for various parameters. It is concluded that the proposed micromechanical model and also the meshless GFD method have a high capability to simulate the composite structures under shock loadings, which are reinforced by FGGPLs. It is shown that the modified micromechanical model and solution technique based on the meshless GFD method are accurate. Also, the time histories of the field variables are shown for various parameters.

• Steel and Composite Structures
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• 제26권5호
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• pp.533-547
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• 2018

In this paper the time-dependent creep analysis of a thick-walled FG cylinder with finite length subjected to axisymmetric mechanical and thermal loads are presented. First order shear deformation theory (FSDT) is used for description of displacement components. Inner and outer temperatures and outer pressure are considered as thermo-mechanical loadings. Both thermal and mechanical loadings are assumed variable along the axial direction using the sinusoidal distribution. To find temperature distribution, two dimensional heat transfer equation is solved using the required boundary conditions. The energy method and Euler equations are employed to reach final governing equations of the cylinder. After determination of elastic stresses and strains, the creep analysis can be performed based on the Yang method. The results of this research indicate that the boundaries have important effects on the responses of the cylinder. The effect of important parameters of this analysis such as variable loading, non-homogeneous index of functionally graded materials and time of creep is studied on the behaviors of the cylinder.

• Composites Research
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• 제26권1호
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• pp.7-13
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• 2013

본 연구에서는 특수강과 복합재료를 사용한 이중구조 실린더의 설계를 위한 해석에 대해서 기술하였다. 특수강과 복합재의 이중구조는 제품의 특성에 적합한 물성을 유지하면서도 무게를 절감해 줄 수 있으며, 이로 인해 고탄성 저중량을 필요로 하는 각종 지상무기 산업분야와 항공분야, 스포츠 관련 분야 등에 점차 확대 적용되고 있다. 따라서 본 연구에서는 하나의 설계에 복합재의 적층각, 종류 등을 바꾸어 가며 이중구조의 설계에 가장 적합한 복합재 적용 방법을 찾기 위해 해석을 실시하였다. 또한 해석의 결과 값들의 비교를 통해 본 연구 설계목표에 가장 알맞은 복합재 적용 방법을 제시하였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.137-140
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• 2005

Resin transfer molding (RTM) is one of the most popular processes for producing fiber reinforced polymer composites. In the manufacture of complex thick composite structures, analysis on flow front advancement on the resin impregnating the multi-layered fiber preform is helpful for the optimization of the process. In this study, three-dimensional mold filling simulation of RTM is carried out by using CVFEM (Control Volume Finite Element Method). On the assumption of isothermal flow of Newtonian fluid, Darcy’s law and continuity equation are used as governing equations. Different permeability tensors employed in each layer are obtained by experiments. Numerically predicted flow front is compared with experimental one in order to validate the numerical results. Flow simulations are conducted in the two mold geometries, rectangular plate and hollow cylinder. Permeability tensor of each layer preform in Cartesian coordinate system is transformed to cylinder coordinates system so that the flow within the multi-layered preforms of the hollow cylinder can be calculated exactly. Our emphasis is on the three dimensional flow analysis for circular three-dimensional braided preform, which shows outstanding mechanical properties such as high impact strength and toughness compared with other conventional two-dimensional laminar-structured preforms.

• Composites Research
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• 제23권2호
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• pp.1-9
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• 2010

본 연구는 실린더 내부가 경사가능재료로 코팅된 두꺼운 벽을 가진 실린더의 겉보기 파괴인성치를 해석한 것이다. 실린더는 내부로부터 반경방향의 단일 모서리 균열이 내재되어 있으며, 균열면과 내면에는 내압을 받고 있는 것으로 가정하였다. 소결온도로부터 냉각 결과 균일한 열팽창계수로 인해 실린더에는 비적합 고유스트레인이 생성되었다. 기존의 연구에서 소개된 응력확대계수 평가법에 기초해 겉보기 파괴인성치를 계산하였다. 본 연구에서는 TiC/$Al_{2}O_{3}$ FGM 코팅된 실린더를 사용하였고 겉보기 파괴인성치의 수치적인 결과를 도식화하였다. 재료분포프로파일, 실린더 벽 두께, 적용온도와 코팅두께등이 겉보기 파괴인치에 미치는 영향이 상세히 조사되었으며, 이러한 모든 인자는 실린더의 겉보기 파괴인성치를 조절하는데 중요한 역할을 하는 것으로 밝혀졌다.

• Steel and Composite Structures
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• 제16권5호
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• pp.521-531
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• 2014

In this paper we consider a periodic solution for nonlinear free vibration of conservative systems for thick circular sector slabs. In Energy Balance Method (EBM) contrary to the conventional methods, only one iteration leads to high accuracy of the solutions. The excellent agreement of the approximate frequencies and periodic solutions with the exact ones could be established. Some patterns are given to illustrate the effectiveness and convenience of the methodology. Comparing with numerical solutions shows that the energy balance method can converge to the numerical solutions very rapidly which are valid for a wide range of vibration amplitudes as indicated in this paper.