• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.164-165
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• 2006

Carbon nanotube(CNT)-reinforced poly(ethylene-co-ethyl acrylate)(EEA) nanocomposites were prepared by melt mixing with a Haake internal mixer. The CNT loading was vaned from 0 to 20 wt%. The changes m CNT dispersion and shape were investigated with FE-SEM observation with and without the Tensile strain of 40%. The CNT was protruded over the fracture surface upon Tensile strain, which is a very interesting behavior.

• Steel and Composite Structures
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• 제32권5호
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• pp.671-686
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• 2019

Active control of solar panels with honeycomb core and carbon nanotube reinforced composite (CNTRC) facesheets for smart structures using piezoelectric patch sensor and actuator to reduce the amplitude of vibration is a lack of the previous study and it is the novelty of this research. Of active control elements are piezoelectric patches which act as sensors and actuators in many systems. Their low power consumption is worth mentioning. Thus, deriving a simple and efficient model of piezoelectric patch's elastic, electrical, and elastoelectric properties would be of much significance. In the present study, first, to reduce vibrations in composite plates reinforced by carbon nanotubes, motion equations were obtained by the extended rule of mixture. Second, to simulate the equations of the system, up to 36 mode shape vectors were considered so that the stress strain behavior of the panel and extent of displacement are thoroughly evaluated. Then, to have a more acceptable analysis, the effects of external disturbances (Aerodynamic forces) and lumped mass are investigated on the stability of the system. Finally, elastoelectric effects are examined in piezoelectric patches. The results of the present research can be used for micro-vibration suppression in satellites such as solar panels, space telescopes, and interferometers and also to optimize active control panel for various applications.

• Steel and Composite Structures
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• 제42권1호
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• pp.23-32
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• 2022

In this paper, a nonlinear numerical method to solve the large deflection problem is introduced. And the non-dimensional load-deflection behavior of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) plates is parametrically investigated. The large deflection problem is formulated according to the von Kármán nonlinear theory and the (1,1,0)^* hierarchical model, and it is approximated by 2-D natural element method (NEM). The shear locking phenomenon is suppressed by the selectively reduced integration method. The nonlinear matrix equations are solved by combining the incremental loading scheme and the Newton-Raphson iteration method. The proposed method is validated from the benchmark experiments, where the propose method shows an excellent agreement with the reference methods. The nonlinear behavior of FG-CNTRC plates is evaluated in terms of the non-dimensional load-deflection curve, and it is parametrically investigated with respect to the existence/non-existence and gradient pattern of CNTs, the width-to-thickness and aspect ratios of plates and the type of boundary conditions. The non-dimensional central deflection is significantly reduced when CNTs and added, and it decreases with the volume fraction of CNTs. But, it shows a uniform increase in proportion to the width-to-thickness and aspect ratios. Both the gradient pattern of CNTs and the type of boundary conditions do also show the remarkable effects.

• Steel and Composite Structures
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• 제42권2호
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• pp.243-256
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• 2022

A coupled finite element method (FEM)-boundary element method (BEM) for analyzing the hydroelastic response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) floating plates under moving loads is firstly introduced in this article. For that aim, the plate displacement field is described utilizing a generalized shear deformation theory (GSDT)-based FEM, meanwhile the linear water-wave theory (LWWT)-relied BEM is employed for the fluid hydrodynamic modeling. Both computational domains of the plate and fluid are coincidentally discretized into 4-node Hermite elements. Accordingly, the C1-continuous plate element model can be simply captured owing to the inherent feature of third-order Hermite polynomials. In addition, this model is also completely free from shear correction factors, although the shear deformation effects are still taken into account. While the fluid BEM can easily handle the free surface with a lower computational effort due to its boundary integral performance. Material properties through the plate thickness follow four specific CNT distributions. Outcomes gained by the present FEM-BEM are compared with those of previously released papers including analytical solutions and experimental data to validate its reliability. In addition, the influences of CNT volume fraction, different CNT configurations, water depth, and load speed on the hydroelastic behavior of FG-CNTRC plates are also examined.

• Steel and Composite Structures
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• 제44권2호
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• pp.155-169
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• 2022

In the present paper an analytical model was developed to study the non-linear vibrations of Functionally Graded Carbon Nanotube (FG-CNT) reinforced doubly-curved shallow shells using the Multiple Scales Method (MSM). The nonlinear partial differential equations of motion are based on the FGM shallow shell hypothesis, the non-linear geometric Von-Karman relationships, and the Galerkin method to reduce the partial differential equations associated with simply supported boundary conditions. The novelty of the present model is the simultaneous prediction of the natural frequencies and their mode shapes versus different curvatures (cylindrical, spherical, conical, and plate) and the different types of FG-CNTs. In addition to combining the vibration analysis with optimization algorithms based on the genetic algorithm, a design optimization methode was developed to maximize the natural frequencies. By considering the expression of the non-dimensional frequency as an objective optimization function, a genetic algorithm program was developed by valuing the mechanical properties, the geometric properties and the FG-CNT configuration of shallow double curvature shells. The results obtained show that the curvature, the volume fraction and the types of NTC distribution have considerable effects on the variation of the Dimensionless Fundamental Linear Frequency (DFLF). The frequency response of the shallow shells of the FG-CNTRC showed two types of nonlinear hardening and softening which are strongly influenced by the change in the fundamental vibration mode. In GA optimization, the mechanical properties and geometric properties in the transverse direction, the volume fraction, and types of distribution of CNTs have a considerable effect on the fundamental frequencies of shallow double-curvature shells. Where the difference between optimized and not optimized DFLF can reach 13.26%.

• 한국재난정보학회 논문집
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• 제17권4호
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• pp.839-847
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• 2021

연구목적: 본 연구에서는 휨을 받는 탄소 나노튜브 보강 기능경사복합재 판의 구조적 거동을 해석하였다. 이를 위해, 등기하해석과 고차전단변형이론을 결합한 수치해석 방법을 이용하였다. 연구방법: 전단보정계수를 사용하지 않고 기하학적 비선형성을 고려할 수 있는 고차전단변형이론을 통하여 휨이 작용하는 탄소 나노튜브 보강 기능경사복합재 판의 비선형 거동방정식을 유도하였으며, 수정된 Newton-Raphson 반복 기법을 사용하여 등기하해석방법에 기반한 시스템 방정식의 해를 구하였다. 연구결과: 탄소 나노튜브의 배치 양상, 폭-두께 비 및 경계조건은 휨을 받는 탄소 나노튜브 보강 기능경사복합재 판의 구조적 거동에 많은 영향을 끼침을 확인하였다. 결론: 제안된 고차전단변형이론에 근거한 등기하해석 방법은 휨을 받는 탄소 나노튜브 보강 기능경사복합재 판의 구조적 거동을 정확하고 효과적으로 해석하는 것을 알 수 있었다.

• Structural Engineering and Mechanics
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• 제67권4호
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• pp.403-415
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• 2018

In the present study, nonlinear dynamic response of polymer-CNT-fiber multiscale nanocomposite plate resting on elastic foundations in thermal environments using the finite element method is performed. In this regard, the governing equations are derived based on Inverse Hyperbolic Shear Deformation Theory and von $K{\acute{a}}rm{\acute{a}}n$ geometrical nonlinearity. Three type of distribution of temperature through the thickness of the plate namely, uniform linear and nonlinear are considered. The considered element is C1-continuous with 15 DOF at each node. The effective material properties of the multiscale composite are calculated using Halpin-Tsai equations and fiber micromechanics in hierarchy. The carbon nanotubes are assumed to be uniformly distributed and randomly oriented through the epoxy resin matrix. Five types of impulsive loads are considered, namely the step, sudden, triangular, half-sine and exponential pulses. After examining the validity of the present work, the effects of the weight percentage of SWCNTs and MWCNTs, nanotube aspect ratio, volume fraction of fibers, plate aspect, temperature, elastic foundation parameters, distribution of temperature and shape of impulsive load on nonlinear dynamic response of CNT reinforced multi-phase laminated composite plate are studied in details.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.13-22
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• 2024

The nonlinear snap-through buckling of functionally graded (FG) carbon nanotube reinforced composite (CNTRC) curved tubes is analytically investigated in this research. It is assumed that the FG-CNTRC curved tube is supported on a three-parameter nonlinear elastic foundation and is subjected to the uniformly distributed pressure and thermal loads. Properties of the curved nanocomposite tube are distributed across the radius of the pipe and are given by means of a refined rule of mixtures approach. It is also assumed that all thermomechanical properties of the nanocomposite tube are temperature-dependent. The governing equations of the curved tube are obtained using a higher-order shear deformation theory, where the traction free boundary conditions are satisfied on the top and bottom surfaces of the tube. The von Kármán type of geometrical non-linearity is included into the formulation to consider the large deflection in the curved tube. Equations of motion are solved using the two-step perturbation technique for nanocomposite curved tubes which are simply-supported and clamped. Closed-form expressions are provided to estimate the snap-buckling resistance of FG-CNTRC curved pipes rested on nonlinear elastic foundation in thermal environment. Numerical results are given to explore the effects of the distribution pattern and volume fraction of CNTs, thermal field, foundation stiffnesses, and geometrical parameters on the instability of the curved nanocomposite tube.

• Advances in nano research
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• 제14권1호
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• pp.27-43
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• 2023

This article investigates the energy harvesting characteristics of a magneto-electro-elastic (MEE) cantilever beam reinforced with carbon nanotubes (CNT) under transverse vibration. To this end, the well-known lumped parameter model is used to represent the coupled multiphysics problem mathematically. The proposed system consists of the MEE-CNT layer on top and an inactive substrate layer at the bottom. The substrate is considered to be made of either an isotropic or composite material. Basic laws such as Gauss's Law, Newton's Law and Faraday's Law are used to arrive at the governing equations. Surface electrodes across the beam are used to harvest the electric potential produced, together with a wound coil, for the generated magnetic potential. The influence of various distributions of the CNT and its volume fraction, substrate material, length-to-thickness ratio, and thickness ratio of substrate to MEE layer on the energy harvesting behaviour is thoroughly discussed. Further, the effect of external resistances and changes in substrate material on the response is analysed and reported. The article aims to explore smart material-based energy harvesting systems, focusing on their behaviour when reinforced with carbon nanotubes. The results of this study may lead to an improved understanding of the design and analysis of CNT-based smart structures.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.35-38
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• 2004

Graphite nanofiber (GNF) and carbon nanotube (CNT) are novel fiber reinforcing materials which have outstanding physical and mechanical properties. Aluminum matrix composites reinforced graphite nanofiber were fabricated by conventional powder metallurgy (PM) method. The composites were prepared through ultrasonication, ball milling, and hot isostatic pressing. A uniform distribution of GNF in aluminum matrix could be obtained. To measure the mechanical properties of GNF-Al composites testings were done in indentation and compression. The compressive strength was enhanced according to reinforcing graphite nanofiber while the hardness was decreased. This study makes the high performance composites for future applications.