• Title/Summary/Keyword: elastic composites

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Thermo-Elastic Analysis, 3-Dimensional Stress Analysis and Design of Carbon/Carbon Brake Disk (탄소/탄소 브레이크 디스크의 열탄성 해석과 3차원 응력해석 및 설계)

  • 오세희;유재석;김천곤;홍창선;김광수
    • Composites Research
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    • v.15 no.1
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    • pp.41-52
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    • 2002
  • This paper presents the thermo-elastic analysis for searching the behavior of carbon/carbon brake system during the braking period and the 3-D stress analysis to find the shape of the brake disk which is safe to the failure. The mechanical properties of the carbon/carbon brake disk were measured for both in-plane and out of plane directions. The mechanical properties were used as the input of the thermo-elastic analysis and 3-dimensional stress analysis for the brake disk. The gap between rotor clip and clip retainer is an important parameter in the loading transfer mechanism of the rotor disk. The change of gap was considered both the mechanical deformation and thermal deformation. Because the rotor clip and clip retainers were not contacted, they were excluded from the analysis model. Rotor disk was modeled by using the cyclic symmetry condition. The contact problems between rotor clip and key drum as well as between rotor disk and rotor were considered. From the results of the 3-D stress analysis, the stress concentration at the key hole of the brake disk was confirmed. The stress distributions were studied thor the variation of the rotation angle of the contact surface and the radius of curvature at the key hole part.

Thermoplastic Film Infusion Process for Long Fiber Reinforced Composites Using Rubber Expandable Tools (고무 치공구와 필름 함침공정을 이용한 열가소성 장섬유 복합재료 성형공정 연구)

  • Kim, Dong-Wook;An, Young-Sun;Lee, Young-Kwan;Kim, Seong-Woo;Nam, Jae-Do
    • Polymer(Korea)
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    • v.25 no.1
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    • pp.122-132
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    • 2001
  • Thermoplastic film infusion process was investigated by using a rubber tool, which intrinsically contains a thermally-expandable characteristic and effectively compensates for the pressure loss caused by thermoplastic polymer infusion. Increasing temperature up to the melting temperature of matrix, the polymer melt subsequently infused into the dry fabric, but the pressure was successfully sustained by the rubber tool. Even with the decreased resin volume, the rubber tool produced sufficiently high elastic force for continuous resin infusion. Combining D'Arcy's law with the compressibility of rubber tool and elastic fiber bed, a film infusion model was developed to predict the resin infusion rate and pressure change as a function of time. In addition, the film infusion process without the rubber tool was viewed and analyzed by a compression process of the elastic fiber bed and viscous resin melt. The compressibility of fiber bed was experimentally measured and the multiple-step resin infusion was well described by the developed model equations.

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Determination of Strain Energy Function of Rubber Materials Considering Stress Softening Behavior (응력연화거동을 고려한 고무 재료의 변형률 에너지 함수 결정)

  • Kim, W.S.;Hong, S.I.
    • Elastomers and Composites
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    • v.42 no.3
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    • pp.168-176
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    • 2007
  • When the rubber vulcanizates reinforced with carbon black or silica are subjected to cyclic loading from its virgin state, the stress required on reloading is less than that on the initial loading. This stress softening phenomenon is referred to as the Mullins effect. The strain energy function of rubber vulcanizates was investigated using theory of pseudo-elasticity incorporated damage parameter that Ogden and Roxburgh have proposed to describe the damage-induced stress softening effect in rubber-like solids. The quasi-static cyclic loading test was performed using the NR-SBR vulcanizates reinforced with carbon black, and then the effect of a damage parameter to stress-strain curve in reloading and subsequent reloading paths was studied. The strain energy function of the rubber vulcanizates with a different filler content was also evaluated.

Numerical Prediction of elastic Material Properties of Composites by A Constrained Nonlinear Optimization Method (구속적 비선형 최적화에 의한 합성재료 탄성물성치의 수치적 예측)

  • 신수봉;고현무
    • Computational Structural Engineering
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    • v.10 no.2
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    • pp.225-232
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    • 1997
  • Material properties of a new composite composed of components with known material properties are usually investigated through experiments. Elastic modulus and Poisson's ratio are measured at various volume fractions of mixed components and utilized as the base information on an analytical model for predicting the mechanical behaviors of a structure constructed by the composite. Elastic material properties of a composite at various volume fractions are numerically estimated by minimizing the error between the static displacements computed from a model for the composite and those computed from a model of homogeneous and isotropic material. A finite element model for a composite is proposed to distribute different types of material components easily into the model depending on the volume fraction. Then, the material properties of a composite filled with solid mircospheres are predicted numerically through a sample study and the estimated results are compared with experimental results and some theoretical equations.

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Bending of steel fibers on partly supported elastic foundation

  • Hu, Xiao Dong;Day, Robert;Dux, Peter
    • Structural Engineering and Mechanics
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    • v.12 no.6
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    • pp.657-668
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    • 2001
  • Fiber reinforced cementitious composites are nowadays widely applied in civil engineering. The postcracking performance of this material depends on the interaction between a steel fiber, which is obliquely across a crack, and its surrounding matrix. While the partly debonded steel fiber is subjected to pulling out from the matrix and simultaneously subjected to transverse force, it may be modelled as a Bernoulli-Euler beam partly supported on an elastic foundation with non-linearly varying modulus. The fiber bridging the crack may be cut into two parts to simplify the problem (Leung and Li 1992). To obtain the transverse displacement at the cut end of the fiber (Fig. 1), it is convenient to directly solve the corresponding differential equation. At the first glance, it is a classical beam on foundation problem. However, the differential equation is not analytically solvable due to the non-linear distribution of the foundation stiffness. Moreover, since the second order deformation effect is included, the boundary conditions become complex and hence conventional numerical tools such as the spline or difference methods may not be sufficient. In this study, moment equilibrium is the basis for formulation of the fundamental differential equation for the beam (Timoshenko 1956). For the cantilever part of the beam, direct integration is performed. For the non-linearly supported part, a transformation is carried out to reduce the higher order differential equation into one order simultaneous equations. The Runge-Kutta technique is employed for the solution within the boundary domain. Finally, multi-dimensional optimization approaches are carefully tested and applied to find the boundary values that are of interest. The numerical solution procedure is demonstrated to be stable and convergent.

A Study on the Vulcanization Characteristics of SBR/BR Blends Containing Reinforcing Fillers (보강성 충전제가 첨가된 SBR/BR 블렌드의 가황특성에 관한 연구)

  • Lee, Seag
    • Elastomers and Composites
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    • v.33 no.4
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    • pp.274-280
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    • 1998
  • Order of reaction, rate constant, activation energy for vulcanization reaction, crosslinking density, and elastic constant of the network produced by sulfur curing were investigated on the SBR/BR blends containing silica and carbon black under same cure system. The reaction order was shown to be first order regardless of filler types. The carbon black filled rubber compounds showed higher rate constant compared to silica filled compounds. But activation energy appeared to be same regardless of filler type and rubber blend ratio. The crosslinking density and elastic constant is higher in the carbon black filled compound compared to silica filled compounds because of strong interaction between rubber and carbon black. On the other hand, crosslinking density and elastic constant were decreased with increasing the butadine rubber content in rubber blends. From the comparison of combined sulfur content in the vulcanized rubber, sulfur content in the silica filled compound become constant 20min later after reaction initiates but sulfur content in the carbon black filled compound become constant 10min later after reaction starts. The silica compound has a longer induction time ($t_2$) and optimum cure time($t_{90}$) compared to those of the carbon black filled compound.

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Optimum Conditions for Improvement of Mechanical and Interfacial Properties of Thermal Treated Pine/CFRP Composites (열처리된 Pine/탄소섬유 복합재료의 기계적 및 계면물성 향상을 위한 최적 조건)

  • Shin, Pyeong-Su;Kim, Jong-Hyun;Park, Ha-Seung;Baek, Yeong-Min;Kwon, Dong-Jun;Park, Joung-Man
    • Composites Research
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    • v.30 no.4
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    • pp.241-246
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    • 2017
  • The brittle nature in most FRP composites is accompanying other forms of energy absorption mechanisms such as fibre-matrix interface debonding and ply delamination. It could play an important role on the energy absorption capability of composite structures. To solve the brittle nature, the adhesion between pines and composites was studied. Thermal treated pines were attached on carbon fiber reinforced polymer (CFRP) by epoxy adhesives. To find the optimum condition of thermal treatment for pine, two different thermal treatments at 160 and $200^{\circ}C$ were compared to the neat case. To evaluate mechanical and interfacial properties of pines and pine/CFRP composites, tensile, lap shear and Izod test were carried out. The bonding force of pine grains was measured by tensile test at transverse direction and the elastic wave from fracture of pines was analyzed. The mechanical, interfacial properties and bonding force at $160^{\circ}C$ treated pine were highest due to the reinforced effect of pine. However, excessive thermal treatment resulted in the degradation of hemicellulose and leads to the deterioration in mechanical and interfacial properties.

Hierarchical Finite-Element Modeling of SiCp/Al2124-T4 Composites with Dislocation Plasticity and Size-Dependent Failure (전위 소성과 크기 종속 파손을 고려한 SiCp/Al2124-T4 복합재의 계층적 유한요소 모델링)

  • Suh, Yeong-Sung;Kim, Yong-Bae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.2
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    • pp.187-194
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    • 2012
  • The strength of particle-reinforced metal matrix composites is, in general, known to be increased by the geometrically necessary dislocations punched around a particle that form during cooling after consolidation because of coefficient of thermal expansion (CTE) mismatch between the particle and the matrix. An additional strength increase may also be observed, since another type of geometrically necessary dislocation can be formed during extensive deformation as a result of the strain gradient plasticity due to the elastic-plastic mismatch between the particle and the matrix. In this paper, the magnitudes of these two types of dislocations are calculated based on the dislocation plasticity. The dislocations are then converted to the respective strengths and allocated hierarchically to the matrix around the particle in the axisymmetric finite-element unit cell model. The proposed method is shown to be very effective by performing finite-element strength analysis of $SiC_p$/Al2124-T4 composites that included ductile failure in the matrix and particlematrix decohesion. The predicted results for different particle sizes and volume fractions show that the length scale effect of the particle size obviously affects the strength and failure behavior of the particle-reinforced metal matrix composites.

Interface Characteristics of Epoxy Composite Treated with Silane Coupling Agent (실란 결합제 처리된 에폭시 수지 복합재료의 계면 특성)

  • Lee, Jae-Yeong;Lee, Hong-Gi;Sim, Mi-Ja;Kim, Sang-Uk
    • Korean Journal of Materials Research
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    • v.11 no.12
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    • pp.1009-1013
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    • 2001
  • The effects of coupling agent on the interface characteristics between epoxy resin and natural zeolite were studied by SEM, optical microscope and universal testing machine (UTM). Epoxy resin as a matrix was diglycidyl ether of bisphenol A (DGEBA)/4,4'-methylene dianiline (MDA)/malononitrile (MN) system and natural zeolite as an inorganic fillet was produced in Korea. With the increment of zeolite content, tensile strength decreased and it was due to the different elastic moduli of two materials. When external stress was loaded on the composites, the stress concentrated on the weakly bonded interface and crack grew easily. To improve the interface characteristics, the surface of the natural zeolite was treated with the silane coupling agent and it was found that the tensile strength was increased. The morphology of the interface showed that the bonding characteristics were modified by coupling agent.

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Load Transfer Behaviors of the Splice-Jointed Fiber Metal Laminates (연결이음 접합된 섬유금속적층판의 하중전달 거동 연구)

  • Roh Hee Seok;Choi Won Jong;Ha Min Su;Choi Heung Soap
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.2 s.233
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    • pp.220-227
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    • 2005
  • In this study, stress-displacement analytic solutions are obtained by a shear lag modeling method constructed for the spliced joint area with a splicing gap in the fiber metal laminate (FML). This gap can be empty or be filled with an adhesive material of elastic modulus $E_a$. Two splicing types are considered for spliced shear models, one for spliced in the center metal layer, the other for spliced in the outer metal layer. It is shown that from the viewpoint of the load transfer efficiency and the avoidability of disbond generation due to the shear and axial stresses at the interface between metal layer and composite layer of the gap-front in the spliced area, the center spliced type (k=2) is much preferable to the outer spliced type (k=1).