• Title/Summary/Keyword: elastic composites

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Dynamic response of size-dependent porous functionally graded beams under thermal and moving load using a numerical approach

  • Fenjan, Raad M.;Ahmed, Ridha A.;Faleh, Nadhim M.;Hani, Fatima Masood
    • Structural Monitoring and Maintenance
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    • v.7 no.2
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    • pp.69-84
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    • 2020
  • Based on differential quadrature method (DQM) and nonlocal strain gradient theory (NSGT), forced vibrations of a porous functionally graded (FG) scale-dependent beam in thermal environments have been investigated in this study. The nanobeam is assumed to be in contact with a moving point load. NSGT contains nonlocal stress field impacts together with the microstructure-dependent strains gradient impacts. The nano-size beam is constructed by functionally graded materials (FGMs) containing even and un-even pore dispersions within the material texture. The gradual material characteristics based upon pore effects have been characterized using refined power-law functions. Dynamical deflections of the nano-size beam have been calculated using DQM and Laplace transform technique. The prominence of temperature rise, nonlocal factor, strain gradient factor, travelling load speed, pore factor/distribution and elastic substrate on forced vibrational behaviors of nano-size beams have been explored.

Actuating Characteristics of a Piezoceramic fiber Composite Actuator (압전섬유 복합재 엑츄에이터의 거동 특성)

  • Koo, Kun-Hyung;Kim, Cheol
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2001.10a
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    • pp.53-56
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    • 2001
  • Piezoelectric Fiber Composites with Interdigitated Electrodes (PFCIDE) were previously introduced as an alternative to monolithic wafers with conventional electrodes for applications of structural actuation. This paper is an investigation into the performance improvement of piezoelectric fiber composite actuators by changing the matrix material and actuator shape. This paper presents a modified micro-electromechanical model and numerical analyses of piezoelectric fiber/piezopolymer matrix composite actuator with interdigitated electrodes (PFPMIDE). Numerical analyses show that the shape of the graphite/epoxy composite plate with the PFPMIDE may be controlled by judicious choice of voltages, piezoelectric fiber angles, and elastic tailoring of the composite plate.

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Evaluation of Elastic Modulus in a Particulate Reinforced Composite by Shape Memory Effect (형상기억입자 강화 복합체의 탄성계수 평가)

  • Kim, Hong-Geon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.1
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    • pp.25-31
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    • 2001
  • The theoretical modeling to predict the modulus of elasticity by the shape memory effect of dispersed particles in a metal matrix composite was studied. The modeling approach is based on the Eshelbys equivalent inclusion method and Mori-Tanakas mean field theory. The calculation was performed on the TiNi particle dispersed Al metal matrix composites(PDMMC) with varying volume fractions and prestrains of the particle. It was found that the prestrain has no effect on the Yonugs modulus of PDMMC but the volume fraction does affects it. This approach has an advantage of definite control of Youngs modulus in PDMMCs.

Compressive and Fracture Characteristics of Seawater-abrobed Carbon-Epoxy Composite under Hydrostatic Pressure Environment (정수압력에 따른 해수흡수된 Carbon/Epoxy 복합재의 압축 및 파괴특성에 대한 연구)

  • 이지훈;이경엽;김현주
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.438-441
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    • 2004
  • In this study, we investigated compressive characteristics of seawater-absorbed carbon-epoxy composite under hydrostatic pressure environment. The hydrostatic pressures applied were 0.1 MPa, 100 MPa, 200 MPa, and 270 MPa. The results showed that the compressive elastic modulus increased about 10 % as the hydrostatic pressure increased from 0.1 MPa to 200 MPa. The modulus increased 2.3 % more as the pressure increased to 270 MPa. Fracture strength and fracture strain increased with pressure in a linear fashion. Fracture strength increased 28 % and fracture strain increased 8.5 % as the hydrostatic pressure increased from 0.1 MPa to 270 MPa.

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Fatigue Life Prediction of Fiber-Reinforced Composite Materials having Nonlinear Stress/Strain Behavior (비선형 변형 거동을 갖는 섬유강화 복합재료의 피로수명 예측)

  • 이창수;황운봉
    • Composites Research
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    • v.12 no.4
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    • pp.1-7
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    • 1999
  • Fatigue life prediction of matrix dominated composite laminates, which have a nonlinear stress/strain response, was studied analytically and experimentally. A stress function describing the relation of initial fatigue modulus and elastic modulus was used in order to consider the material nonlinearty. New modified fatigue life prediction equation was suggested based on the fatigue modulus and reference modulus concept as a function of applied stress. The prediction was verified by torsional fatigue test using crossply carbon/epoxy laminate tubes. It was shown that the proposed equation has wide applicability and good agreement with experimental data.

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A Study of Dynamic Viscoelastic Properties on Temperatures of Natural Rubber (천연고무의 온도에 따른 동적 점탄성 연구)

  • Lee, Bum-Chul;Yoo, Kil-Sang
    • Elastomers and Composites
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    • v.32 no.1
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    • pp.29-36
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    • 1997
  • The change of elastic modulus(E'), loss modulus(E"), and loss $tangent(tan{\delta})$ were investigated on condition of double strain amplitude (DSA) at temperature of $-40{\sim}80^{\circ}C$ for carbon black filled natural rubber. E', E", and $tan{\delta}$ were increased as it closed to the glass transition temperature due to decrease of rubber network flexibility and carbon black agglomerate interaction. In the micro strain range, energy loss showed maximum value because of the chain slippage in rubber matrix, but the regeneration of carbon black agglomerate and rubber matrix affected decrease of energy loss over the mid-range strain. As a results of regression analysis, $E'\;_{max}$ correlation with ${\Delta}E'$ $(E'\;_{0.4%DSA}-E'\;_{2.0%DSA})$ showed linear relationship.

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Properties of Specialty Cellulose Fiber Reinforced Concrete at Early Ages (특수 가공된 셀룰로오스섬유보강 콘크리트의 초기 특성)

  • 원종필;박찬기
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.04a
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    • pp.349-354
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    • 1999
  • Specialty cellulose fibers processed for the reinforcement of concrete offer relatively high levels of elastic modulus and bond strength. The hydrophilic surfaces of specialty cellulose fibers facilitate their dispersion and bonding in concrete. Specialty cellulose fibers have small effective diameters which are comparable to the cement particle size, and thus promote close packing and development of dense bulk and interface microstructure in the matrix. The relatively high surface area and the close spacing of specialty cellulose fibers when combined with their desirable mechanical characteristic make them quite effective in the suppression and stabilization of microcracks in the concrete matrix. The properties of fresh mixed specialty cellulose fiber reinforced concrete and the contribution of specialty cellulose fiber to the restrained shrinkage crack reduction potential of cement composites at early age and theirs evaluation are presented in this paper. Results indicated that specialty cellulose fiber reinforcement showed an ability to reduce the total area significantly (as compared to plain concrete and polypropylene fiber reinforced concrete.

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Microstructure and Mechanical Properties of the $Al_2O_3-SiC$ Ceramics Produced by Melt Oxidation (용융산화법으로 제조한 $Al_2O_3-SiC$ 세라믹스의 미세구조와 기계적 성질)

  • ;H. W. Hennicke
    • Journal of the Korean Ceramic Society
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    • v.31 no.10
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    • pp.1169-1175
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    • 1994
  • Five Al2O3/SiC/metal composites with four different particle sizes of green SiC abrasive grains are grown by the directed oxidation of an commercially available Al-alloy. Oxidation was conducted in air at 100$0^{\circ}C$, 96 hours long. Slip casted SiC-fillers were placed on the alloy or SiC powder deposited up to the required layer thickness. Their microstructures are described and measurements of density, elastic constants, frexural strength, fracture toughness and work of fracture are reported. The results are compared with those of commercial dense sintered Al2O3. The properties of produced materials have a strong relationship to not only the properties of Al2O3, SiC, Al and Si but also to the phase share and phase distribution. The composite materials are dense (0.5% porosity), tough (KIC = 3.4~6.4 MPa{{{{ SQRT { m} }}), strong ({{{{ sigma }}B = 170~345 MPa) and reasonably shrinkage free producible. The reinforcements is attained mainly through the plastic deformation of ductile metal phase.

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Low-Velocity Impact Characterizations of 3D Orthogonal Woven Composite Plate (3D 직교 직물 복합재료의 충격 거동 및 특성에 관한 수치해석)

  • 지국현;김승조
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.170-174
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    • 2002
  • In this study, the material characterization and the dynamic behavior of 3D orthogonal woven composite materials has been studied under transverse central low-velocity impact condition by means of the micromechanical model using finite elements. To build up the micromechanical model considering tow spacing and waviness, an accurate unit structure is stacked in x-y-z direction repeatedly. First, the mechanical properties of 3D orthogonal woven composites are obtained by means of virtual experiment using full scale Finite Element Analysis based on the DNS concepts, and the computed elastic properties are validated by comparison to available experimental results[9]. Second, using the implementation of this validated micromechanical model, 3D transient finite-element analysis is performed considering contact and impact, and the impact behavior of 3D orthogonal woven composite is investigated. A comparison study will be carried out in terms of energy absorption capabilities.

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A Double Cantilever Sandwich Beam Method far Evaluating Frequency Dependence of Dynamic Modulus and Damping Factor of Rubber Materials (고무의 동탄성계수와 손실계수의 주파수 의존성을 평가하기 위한 양팔 샌드위치보 시험법의 연구)

  • 김광우;박진택;이덕보;최낙삼
    • Composites Research
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    • v.14 no.3
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    • pp.69-76
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    • 2001
  • This paper proposes a double cantilever sandwich-beam method fur evaluating the frequency dependence of dynamic characteristics of rubbers. The flexural vibration of a double cantilever sandwich-beam specimen with an inserted rubber layer was studied using a finite element simulation in combination with the sine-sweep test. Quadratic relationships of dynamic elastic modulus and material loss factor of rubbers with frequency were suggested employing the least square error method.

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