• Structural Engineering and Mechanics
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• 제68권1호
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• pp.131-157
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• 2018

In this study, Eringen nonlocal elasticity theory in conjunction with surface elasticity theory is employed to study nonlinear free vibration behavior of FG nano-plate lying on elastic foundation, on the base of Reddy's plate theory. The material distribution is assumed as a power-law function and effective material properties are modeled using Mori-Tanaka homogenization scheme. Hamilton's principle is implemented to derive the governing equations which solved using DQ method. Finally, the effects of different factors on natural frequencies of the nano-plate under hygrothermal situation and various boundary conditions are studied.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.479-482
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• 2004

Laminate Design of a composite tube for a space telescope(Fig. 1) under hygrothermal load is studied. Carpet plots for laminate effective engineering constants are generated and used for selecting the best tube lay-ups satisfying the optomechanical requirements for a space telescope being dimensional1y stable under orbital thermal loading. Despace of the tubes constructed with the selected lay-ups are calculated with a Zig-Zag Triangular Element which accurately represents through thickness stress variations for laminated structures. The effects of moisture absorption when exposed to humidity environment and moisture desorption through outgassing on the dimensional stability are also investigated.

• Journal of Advanced Marine Engineering and Technology
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• 제17권2호
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• pp.52-59
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• 1993

This study is investigated of tensile and fatigue strength for advanced composite materials under hygrothermal environment. The materials used are two types of Carbon/Epoxy reinforced composite materials i.e., 13$0^{\circ}C$ cure-type composite T-1/347, and 18$0^{\circ}C$ cure-type MM-1/982X. These are composed by cross-ply laminates. Test condition is the distilled water of 8$0^{\circ}C$. The separate absorption contents estimated by the Fick's diffusion rule are similar to the experiment results. The tensile strength of T-1/347 wet specimens more increased than that of dry ones, but that of MM-1/982X decreased. The fatigue strengthes of both T-1/347 and MM-1/982X wet specimen more decreased than those of dry specimens.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.994-996
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• 1999

Hygrothermal aging at the elevated temperature induces the long-term degradation of the epoxy resin. We investigated the effects of hydrothermal stress on the dielectric breakdown phenomena of epoxy composite filled with natural zeolite. The cured specimens absorbed the moisture in the autoclave at $120^{\circ}C$. $T_g$ of the deteriorated composite by moisture absorption decreased. The dielectric breakdown strength decreased with the moisture absorption cycle. It was concluded that the thermal stress and the high water-vapour-pressure deteriorated the natural zeolite filled epoxy resin system, consequently and the tree growth rate increased.

• 한국염색가공학회지
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• 제27권3호
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• pp.210-218
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• 2015

In this study, natural substance and mineral materials was used for architectural interior wallpaper. Because natural substance and minerals are environment-friendly material with moisture adsorption and desorption properties. Natural substance and mineral materials was evaluated in moisture adsorption and desorption properties. Also, in the diatomite, the pores were observed on SEM photographs. Thus, it is supposed that moisture adsorption and desorption properties were influenced by the microstructure of the pore. The wallpaper according to the ratio of the mixture was analyzed for physical properties and moisture adsorption & desorption properties. As a result, we developed a wallpaper having excellent hygrothermal performance.

• 한국결정성장학회지
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• 제9권3호
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• pp.347-352
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• 1999

세라믹 애자 건조공정의 유한요소 시뮬레이션으로 건조공정중 애자의 온도분포, 습도분포, 습열응력분포, 그리고 변형형상을 예측하였다. 유한요소 수식화에서 온도구배, 습도구배, 전도, 대류 및 증발을 고려하여 불소성 세라믹의 온도분포와 습도분포를 구하였고, 온도 및 습도변화로 인한 체적 변화로부터 습열응력을 구하였다. 유한요소 수식화를 기초로 컴퓨터 프로그램을 개발하고, 개발된 프로그램을 사용하여 세라믹 애자의 건조공정을 시뮬레이션 하였다.

• Advances in nano research
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• 제8권1호
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• pp.49-58
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• 2020

This paper investigates the vibration characteristics of flexoelectric nanobeams resting on viscoelastic foundation and subjected to magneto-electro-viscoelastic-hygro-thermal (MEVHT) loading. In this regard, the Nonlocal strain gradient elasticity theory (NSGET) is employed. The proposed formulation accommodates the nonlocal stress and strain gradient parameter along with the flexoelectric coefficient to accurately predict the frequencies. Further, with the aid of Hamilton's principle the governing differential equations are derived which are then solved through Galerkin-based approach. The variation of the natural frequency of MEVHT nanobeams under the influence of various parameters such as the nonlocal strain gradient parameter, different field loads, power-law exponent and slenderness ratio are also investigated.

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.433-441
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• 2019

In this paper, geometrically nonlinear static analysis of laminated composite beams is investigated under hygrothermal effect. In the solution of problem, the finite element method is used within the first shear beam theory. Total Lagrangian approach is used nonlinear kinematic model. The geometrically nonlinear formulations are developed for the laminated beams with hygro-thermal effects. In the nonlinear solution of the problem, the Newton-Raphson method is used with incremental displacement. In order to verify of obtained formulations, a comparison study is performed. The effects of the fiber orientation angles, the stacking sequence of laminates, temperature rising and moisture changes on the nonlinear static displacements and configurations of the composite laminated beam are investigated in the numerical results.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제24회 춘계학술대회논문집
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• pp.31-34
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• 2005

미세균열이 생기기 전 $80^{\circ}C$ 물속에서 침수시간이 변함에 따른 $Avimid^{R}$ K3B/IM7 복합재의 습기노화현상에 관하여 연구하였다. $80^{\circ}C$ 물속에서 복합재의 강성을 저하시키는 요인으로는 수지 강성의 저하나 잔류응력의 변화 그리고 섬유와 수지 사이의 계면 손상이다. $80^{\circ}C$ 물속에서 수지에 습기가 포화되는 시간은 500 시간이며 K3B/IM7 복합재에 습기가 포화되는 시간은 100 시간이다. $80^{\circ}C$ 물속에서 수지가 500 시간 가속노화한 후 DSC 시험을 한 결과 $T_{g}는 1\%$ 이내 증가하였으며 무게는 $1.55\%$증가하였다. $80^{\circ}C$ 물속에서 수지의 습기 포화 속도가 복합재의 습기 포화 속도 보다 빨랐다. 500 시간 노화한 후 수지의 파괴인성은 $37\%$ 저하하였으며 100 시간 노화한 후 [+45/0/-45/90]s K3B/IM7 복합재의 미세균열 파괴인성은 $28\%$ 감소하였다.

• 한국추진공학회지
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• 제9권4호
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• pp.23-30
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• 2005

미세균열이 생기기 전 $80^{\circ}C$ 물속에서 침수시간에 따른 $Avimid^(R)$ K3B/IM7 복합재의 습기노화 현상에 관하여 연구하였다. $80^{\circ}C$ 물속에서 복합재의 파괴인성을 저하시키는 요인으로는 수지 파괴인성의 저하나 잔류응력의 변화 그리고 섬유와 수지 사이의 계면 손상이다. $80^{\circ}C$ 물속에서 수지에 습기가 포화되는 시간은 500 시간이며 K3B/IM7복합재에 습기가 포화되는 시간은 100 시간이다. 수지가 500 시간 가속노화한 후 DSC 시험을 한 결과 $T_g$는 1% 이내 증가하였으며, 무게는 $7\times10^{-6}m/s^2$ 확산속도로 1.55% 증가하였다. K3B/IM7복합재에 관하여 물속에서 100시간 지난 후 무게는 $1\times10^{-6}m/s^2$ 확산속도로 0.41% 증가했다. 500 시간 노화한 후 수지의 파괴인성은 41% 저하하였으며 100 시간 노화한 후 ${[+45/0/-45/90]}_s$ K3B/IM7 복합재의 미세균열 파괴인성은 43.8% 감소하였다. 그러므로 $80^{\circ}C$ 수분노화 시험에서 복합재 적층의 파괴인성을 감소시키는 주요 원인은 수지 파괴인성의 저하라고 할 수 있다.