• Title/Summary/Keyword: Multi-layered materials

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Non-linear aero-elastic response of a multi-layer TPS

  • Pasolini, P.;Dowell, E.H.;Rosa, S. De;Franco, F.;Savino, R.
    • Advances in aircraft and spacecraft science
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    • v.4 no.4
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    • pp.449-465
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    • 2017
  • The aim of the present work is to present a computational study of the non-linear aero-elastic behavior of a multi-layered Thermal Protection System (TPS). The severity of atmospheric re-entry conditions is due to the combination of high temperatures, high pressures and high velocities, and thus the aero-elastic behavior of flexible structures can be difficult to assess. In order to validate the specific computational model and the overall strategy for structural and aerodynamics analyses of flexible structures, the simplified TPS sample tested in the 8' High Temperature Tunnel (HTT) at NASA LaRC has been selected as a baseline for the validation of the present work. The von $K{\acute{a}}rm{\acute{a}}n^{\prime}s$ three dimensional large deflection theory for the structure and a hybrid Raleigh-Ritz-Galerkin approach, combined with the first order Piston Theory to describe the aerodynamic flow, have been used to derive the equations of motion. The paper shows that a good description of the physical behavior of the fabric is possible with the proposed approach. The model is further applied to investigate structural and aero-elastic influence of the number of the layers and the stitching pattern.

The Properties of Multi-Layered Optical Thin Films Fabricated by Pulsed DC Magnetron Sputtering (Pulsed DC 마그네트론 스퍼터링으로 제조된 다층 광학박막의 특성)

  • Kim, Dong-Won
    • Journal of the Korean institute of surface engineering
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    • v.52 no.4
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    • pp.211-226
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    • 2019
  • Optical thin films were deposited by using a reactive pulsed DC magnetron sputtering method with a high density plasma(HDP). In this study, the effect of sputtering process conditions on the microstructure and optical properties of $SiO_2$, $TiO_2$, $Nb_2O_5$ thin films was clarified. These thin films had flat and dense microstructure, stable stoichiometric composition at the optimal conditions of low working pressure, high pulsed DC power and RF power(HDP). Also, the refractive index of the $SiO_2$ thin films was almost constant, but the refractive indices of $TiO_2$ and $Nb_2O_5$ thin films were changed depending on the microstructure of these films. Antireflection films of $Air/SiO_2/Nb_2O_5/SiO_2/Nb_2O_5/SiO_2/Nb_2O_5/Glass$ structure designed by Macleod program were manufactured by our developed sputtering system. Transmittance and reflectance of the manufactured multilayer films showed outstanding value with the level of 95% and 0.3%, respectively, and also had excellent durability.

Impact of Anti-Reflective Coating on Silicon Solar Cell and Glass Substrate : A Brief Review

  • Zahid, Muhammad Aleem;Khokhar, Muhammad Quddamah;Cho, Eun-Chel;Cho, Young Hyun;Yi, Junsin
    • Current Photovoltaic Research
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    • v.8 no.1
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    • pp.1-5
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    • 2020
  • The most important factor in enhancing the performance of an optical device is to minimize reflection and increasing transmittance of light for a broad wavelength range. The choice of appropriate coating material is crucial in decreasing reflection losses at the substrate. The purpose of this review is to highlight anti-reflection coating (ARC) materials that can be applied to silicon solar cell and glass substrate for minimizing reflection losses. The optical and electrical behavior of ARC on a substrate is highly dependent on thickness and refractive index (RI) of ARC films that are being deposited on it. The coating techniques and performance of single and multi-layered ARC films after coated on a substrate in a wide range of wavelength spectrum will be studied in the paper.

Analysis of Wave Reflection from an Open-Ended Coaxial Probe Using the FDTD Method (FDTD 방법을 이용한 동축선로 끝단에서의 전파반사 분석)

  • 박기억;손병문;오이석;구연건
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.35D no.10
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    • pp.7-12
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    • 1998
  • The wave reflections from several types of open-ended coaxial probes contacted on the various materials have been analyzed precisely by using the finite-difference time-domain(FDTD) technique in this paper. Due to the coordinate transformation from three-dimension to two-dimension, the computation was performed very efficiently. It was found that the reflection from an open-ended coaxial probe reduces as frequency or diameter of a coaxial line increases. The reflections from multi-layered media were also analyzed by the FDTD method. This analysis technique was verified by comparison with measurements and theoretical computations.

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Thickness Effect of Double Layered Sheet on Burr Formation during Micro-Via Hole Punching Process (미세 비아홀 펀칭 공정 중 이종 재료 두께에 따른 버 생성)

  • 신승용;임성한;주병윤;오수익
    • Transactions of Materials Processing
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    • v.13 no.1
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    • pp.65-71
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    • 2004
  • Recent electronic equipment becomes smaller, more functional, and more complex. According to these trends, LTCC(low temperature co-fired ceramic) has been emerged as a promising technology in packaging industry. It consists of multi-layer ceramic sheet, and the circuit has 3D structure. In this technology via hole formation plays an important role because it provides an electric path for the packaging interconnection network. Therefore via hole qualify is very important for ensuring performance of LTCC product. Via holes are formed on the green sheet that consists of ceramic(before sintering) layer and PET(polyethylene terephthalate) one. In this paper we found the correlation between hole quality and process condition such as PET thickness and ceramic thickness. The shear behavior of double layer sheet by micro hole punching which is different from that of single layer one was also discussed.

Contact Damage and Fracture of Poreclain/Glass-Infiltrated Alumina Layer Structure for Dental Application (치아 응용을 위한 /유리침윤 알루미나 이중 층상구조의 접촉손상 및 파괴)

  • 정연길;여정구;최성설
    • Journal of the Korean Ceramic Society
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    • v.35 no.12
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    • pp.1257-1265
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    • 1998
  • Hertzian contact tests were used to investigate the evolution of fracturedamage in the coating layer as functions of contact load and coating thickness by studying crack patterns in porcelain on glass-infiltrated alumina bilayer system conceived to simulate the crown structure of a tooth. Cone cracks initiated at the coating top surface without delamination at interface and crack propagation to substrate. Preferentially the cracks made multi-cracks at the coating top surface rather than proceeding to interface. The cracks were highly stabilized with wide ranges between the loads to initiate first cracking and to cause final failure im-plying damage-tolerant capability. Finite element modelling was used to evaluate the stress distribution. Maximum tensile stress were responsible for the cracking at the coating layer and had a profound influence on the crack pattern and fracture damage in the layered structure materials.

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Notched Strength Analysis of CRALL Materials by FEM (I) (FEM에 의한 CRALL재의 노치강도 해석(I))

  • Yoon, Han-Ki
    • Journal of Ocean Engineering and Technology
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    • v.13 no.2 s.32
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    • pp.41-50
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    • 1999
  • As for the properties on both the aluminum and the CFRP which are used to make A17075/CFRP multi-layered hybrid composites, CRALL(carbon reinforced aluminum laminate). In the CRALL specimen for rule of mixture, we were analyzed notched strength by finite element method. The results obtained from FEM analysis are as follows; In the unnotch CRALL specimen, the stresses CFRP, epoxy, Al 7075 obtained by finite element method strength solution for A/C0001, when strain is 0.28%, are 1400MPa, 38MPa, 411MPa. respectively and for A/C9991, when strain 0.48%, are 392MPa, 26MPa and 321Mpa, respectively. the solpe of the stress-strain curve by FEM increases in keeping with the hole size and the yield strain decrease to 36% and 55% for A/C9993 and A/C9991 respectively.

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Simulation Technology of 3D Fabrics (3차원 입체 직물의 시뮬레이션 기술)

  • Park, Jung Hyun
    • Textile Coloration and Finishing
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    • v.31 no.3
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    • pp.214-224
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    • 2019
  • This investigation reported the simulation technologies to design the 3-dimensional fabrics such as 3 dimensional multi-layered fabric, 3 dimensional braided fabric and spacer fabric. The simulation system or software has been actively used to develop products of 3 dimensional fabric which can be reduced development costs and time. Thus, many countries such as Japan, Germany, China, and U.K. show great interests on simulation technologies for developing new materials and processes including 3 dimensional fabric field. In this study, simulation systems have been reviewed for the 3 dimensional fabric design system from Mikawa Textile Research Center, Japan; ProCad and ProFab from Karl Mayer and Texion, Germany; xComposites from China; TexGen from Nottingham University, U.K.; TexPro from Young Woo CnI, Korea, respectively.

Fabrication of Ultra-Small Multi-Layer Piezoelectric Vibrational Device Using P(VDF-TrFE-CFE) (P(VDF-TrFE-CFE)를 이용한 초소형 압전 적층형 진동 출력 소자의 제작)

  • Cho, Seongwoo;Glasser, Melodie;Kim, Jaegyu;Ryu, Jeongjae;Kim, Yunjeong;Kim, Hyejin;Park, Kang-Ho;Hong, Seungbum
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.32 no.2
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    • pp.157-160
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    • 2019
  • P(VDF-TrFE-CFE) (Poly (vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)), which exhibits a high electrostriction of about 7%, can transmit tactile output as vibration or displacement. In this study, we investigated the applicability of P(VDF-TrFE-CFE) to wearable piezoelectric actuators. The P(VDF-TrFE-CFE) layers were deposited through spin-coating, and interspaced with patterned Ag electrodes to fabricate a two-layer $3.5mm{\times}3.5mm$ device. This layered structure was designed and fabricated to increase the output and displacement of the actuator at low driving voltages. In addition, a laser vibrometer and piezoelectric force microscope were used to analyze the device's vibration characteristics over the range of ~200~4,200 Hz. The on-off characteristics were confirmed at a frequency of 40 Hz.

A Study on the Dielectric Properties and Mechanical characteristics of Composit Materials due to the High-Temper, and-Humidity (고온.다습하(高溫.多濕下)에서의 복합재료(複合材料)의 수요특성(特性) 및 기계적특성(機械的特性)에 관한 연구(硏究))

  • Lee, Jong-Ho;Lee, Kyu-Chul;Hwang, Yeong-Han;Kim, Hea-Dae;Lee, Tae-Sik;Park, Hong-Tae
    • Proceedings of the KIEE Conference
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    • 1992.07b
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    • pp.750-752
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    • 1992
  • The paper presents the effects of environment on glass-cloth/epoxy composites exposed to humid air were investigated. Tests were performed at temperature 40$^{\circ}C$ and 70$^{\circ}C$ with the materials exposed to humid air at 76% and 90% relative humidity. This investigation surveyed include (a) the moisture absorption and desorption characteristics of single and multi layered composites exposed to steady and to transient ambients, and (b) the resulting changes in tensile strength, dielectric strength, tan $\delta$ and $\varepsilon_{\tau}$ and the effects of environment on these parameters were assessed.

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