• Smart Structures and Systems
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• 제26권4호
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• pp.469-480
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• 2020

This is the first research on the smart control and vibration analysis of a Graphene nanoplatelets (GPLs) Reinforced Composite (GPLRC) porous cylindrical shell covered with piezoelectric layers as sensor and actuator (PLSA) in the framework of numerical based Generalized Differential Quadrature Method (GDQM). The stresses and strains are obtained using the First-order Shear Deformable Theory (FSDT). Rule of the mixture is employed to obtain varying mass density and Poisson's ratio, while the module of elasticity is computed by modified Halpin-Tsai model. The external voltage is applied to sensor layer and a Proportional-Derivative (PD) controller is used for sensor output control. Governing equations and boundary conditions of the GPLRC cylindrical shell are obtained by implementing Hamilton's principle. The results show that PD controller, length to radius ratio (L/R), applied voltage, porosity and weight fraction of GPL have significant influence on the frequency characteristics of a porous GPLRC cylindrical shell. Another important consequence is that at the lower value of the applied voltage, the influence of the smart controller on the frequency of the micro composite shell is much more significant in comparison with the higher ones.

• Journal of Electrochemical Science and Technology
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• 제12권1호
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• pp.74-81
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• 2021

Silicon (Si) is recognized as a promising anode material for high-energy-density lithium-ion batteries. However, under a condition of electrode comparable to commercial graphite anodes with low binder content and a high electrode density, the practical use of Si is limited due to the huge volume change associated with Si-Li alloying/de-alloying. Here, we report a novel core-shell composite, having a reversible capacity of ~ 500 mAh g-1, by forming a shell composed of a mixture of nano-Si, graphite nanosheets and a pitch carbon on a spherical natural graphite particle. The electrochemical measurements are performed using electrodes with 2 wt % styrene butadiene rubber (SBR) and 2 wt.% carboxymethyl cellulose (CMC) binder in an electrode density of ~ 1.6 g cm-3. The core-shell composites having the reversible capacity of 478 mAh g-1 shows the outstanding capacity retention of 99% after 100 cycles with the initial coulombic efficiency of 90%. The heterostructure of core-shell composites appears to be very effective in buffering the volume change of Si during cycling.

• Structural Engineering and Mechanics
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• 제42권2호
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• pp.211-228
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• 2012

Present study deals with the development of finite element based solution methodology to investigate active control of dynamic response of delaminated composite shells with piezoelectric sensors and actuators. The formulation is based on first order shear deformation theory and an eight-noded isoparametric element is used. A coupled piezoelectric-mechanical formulation is used in the development of the constitutive equations. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. A simple negative feedback control algorithm coupling the direct and converse piezoelectric effects is used to actively control the dynamic response of delaminated composite shells in a closed loop employing Newmark's time integration scheme. The validity of the numerical model is demonstrated by comparing the present results with those available in the literature. A number of parametric studies such as the locations of sensor/actuator patches, delamination size and its location, radius of curvature to width ratio, shell types and loading conditions are carried out to understand their effect on the transient response of piezoceramic delaminated composite shells.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 춘계학술발표대회 논문집
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• pp.131-134
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• 2002

Supersonic flutter analysis of cylindrical composite panels with structural damping treatments has been performed using the finite element method based on the layerwise shell theory. The natural frequencies and loss factors of cylindrical viscoelastic composites are computed considering the effects of transversely shear deformation. The panel flutter of cylindrical composite panels is analyzed considering structural damping effect. Various damping characteristics for unconstrained layer damping, constrained layer damping, and symmetrically co-cured sandwich laminates are compared with those of an original base panel in view of aeroelastic stabilities.

• 한국응용과학기술학회지
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• 제21권1호
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• pp.69-75
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• 2004

In this study, various model composite latexes were synthesized using n-butyl acrylate and methyl methacrylate as comonomers by seeded multi-staged emulsion polymerization. Monodispersed model composite latex particles with size of 190 nm and polydispersity index of 1.05, which have various morphology including random copolymer particle, soft-core/hard-shell particle, hard-core/soft shell particle, and gradient-type copolymer particle, homopolymers particles were prepared. The designed morphology of model composite particles were confirmed.

• 한국소음진동공학회논문집
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• 제11권9호
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• pp.475-485
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• 2001

A study on the structural analysis of the composite laminated cylindrical shell which has simply supported boundary conditions at both ends, was performed. The results were used into the neural networks. Neural networks identify the load characteristics of the composite shells. Momentum Backpropagation which the learning rate can be varied was developed. Input patterns consist of strains at 9 side points which is divided equally. Output layers are the load characteristics. Developed program was used for the training. The training with variable learning rate was converged close to real oad characteristics. Inverse engineering can be applicable to the composite laminated cylindrical shells with developed neural networks.

• Steel and Composite Structures
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• 제17권6호
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• pp.867-890
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• 2014

This paper deals with the geometric nonlinear bending analysis of laminated composite stiffened plates subjected to uniform transverse loading. The eight-noded degenerated shell element and three-noded degenerated curved beam element with five degrees of freedom per node are adopted in the present analysis to model the plate and stiffeners respectively. The Green-Lagrange strain displacement relationship is adopted and the total Lagrangian approach is taken in the formulation. The convergence study of the present formulation is carried out first and the results are compared with the results published in the literature. The stiffener element is reformulated taking the torsional rigidity in an efficient manner. The effects of lamination angle, depth of stiffener and number of layers, on the bending response of the composite stiffened plates are considered and the results are discussed.

• Elastomers and Composites
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• 제45권1호
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• pp.7-11
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• 2010

본 논문에서는 polyethyleneimine (PEI)를 커플링제로 사용하여 간단한 공정을 통하여 아세틸렌 블랙/실리카 복합체 입자를 제조하였다. 복합체 입자는 PEI를 아세틸렌 블랙 표면에 흡착시키고 졸-겔 합성공정을 통하여 실리카를 아세틸렌 블랙 위에서 합성하는 두단계 공정을 통하여 제조되었다. 복합체 입자의 모폴로지 분석 결과 실리카가 아세틸렌 블랙위에 존재하는 core-shell 구조를 확인하였으며, 표면에 상당한 미세기공이 존재함을 알 수 있었다.

• 한국산학기술학회논문지
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• 제14권11호
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• pp.5979-5986
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• 2013

본 연구에서는 복합재료 적층 쉘 구조의 기하학적 비선형 동적 거동을 상세 분석하였다. Sanders의 1차 전단 변형 쉘이론 및 비선형 방정식을 기반하여, 비선형 동적 방정식의 해는 Newmark 방법과 Newton-Raphson 반복법을 혼용하여 적용하여 산정하였다. 본 연구에서 개발한 유한요소 해석프로그램을 사용하여 쉘의 곡률, 화이버 보강각도 및 적층 배열의 변화가 적층 쉘의 기하학적 비선형 동적 거동에 미치는 영향을 상세 분석하였다. 몇 가지 수치해석 결과는 기존 문헌으로부터 얻어진 결과와 잘 일치하는 것으로 나타났다. 본 연구의 새로운 결과는 최대 동적변위에 대한 적층 쉘 구조의 곡률, 화이버 보강각도 그리고 적층 배열 형식과의 중요한 상호관계를 보여준다. 몇 가지 수치해석 예제는 동적 특성을 고려한 적층 쉘 구조를 상세 설계하는데 필요한 가이드라인을 제시할 수 있을 것으로 기대된다.

• Composites Research
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• 제37권3호
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• pp.186-189
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• 2024

본 연구는 나노필러가 혼합된 열가소성 탄소섬유강화 복합재료(Carbon fiber reinforced thermoplastic polymer, CFRTP)의 물성을 비교 평가하였다. Polyamide 6 (PA6) 수지에 Multi-wall carbon nano tube (MWCNT), Silicon oxide, Core shell rubber, Aramid nano fiber 등의 다양한 나노필러를 혼합한 후, 이를 기지재(Matrix)로 탄소섬유강화복합 재료(CFRP)를 제조하여 그 물성을 측정하였다. 나노필러의 종류와 혼합비율에 따라, 인장강도, 층간계면결합력 (Inter-laminar shear strength), Izod 충격 강도 등이 측정되었다. 인장 강도와 충격 강도의 경우 Core shell rubber를 혼합한 경우 가장 높은 물성을 가졌으나, 계면결합력은 silicon oxide를 1 wt.% 이하 혼합하였을 때 최적값을 가졌다.