• Title/Summary/Keyword: 평직 복합재료

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Mechanical Properties Anisotropy of Plain Weave Glass Fabric Reinforced Epoxy Resin Laminates (평직유리섬유강화 에폭시 적층판의 기계적 특성 이방성)

  • Kim, Yon-Jig
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.3
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    • pp.15-21
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    • 2009
  • The anisotropic mechanical properties were measured for the three orthogonal orientations of plain weave glass fabric reinforced epoxy resin laminate. In tensile and flexural tests, axial and edge type specimens failed by pull-out of warp and fill yarns, respectively. In contrast, the thickness type specimens failed by adhesive failure process. Longitudinal cracking occurred in several of the edge type specimens during tensile test. That cracking caused pop-in in the stress-strain curve. Defects induced by improper coupon machining caused that cracking.

Non-Linear Behavior Analysis for Stratospheric Airship Envelope (성층권 비행선 기낭 막재료에 대한 비선형 거동 연구)

  • Suh Young Wook;Woo Kyeongsik
    • Composites Research
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    • v.18 no.2
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    • pp.30-37
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    • 2005
  • In this paper, geometrically non-linear finite element analyses were performed to study the mechanical behavior of the material system of the envelope of stratospheric airships. The microstructure of the load-bearing plain weave layer was identified and modeled. The Updated Lagrangian formulation was employed to consider the geometric non-linearity as well as the induced structural non-linearity for the fiber tows. The stress-strain behavior was predicted and the effective elastic modulus was calculated by numerical experiments. It was found the non-linear stress-strain curves were largely different from those by linear analysis. And non-linear elastic moduli were much higher than linear elastic moduli. The difference was more distinguishable when the tow waviness ratio was smaller.

Strength of Glass/Epoxy Fabric Joints under the Pin-Loading (핀하중을 받는 유리/에폭시 평직 적층판의 체결부 강도)

  • 박노희;권진희;김종훈;변준형;양승운
    • Composites Research
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    • v.15 no.2
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    • pp.1-10
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    • 2002
  • The strength of glass/epoxy fabric joints under pin-loading is estimated based on the characteristics length method and experiment. To investigate the effect of finite element idealization for the contact between pin and laminate, three modeling cases are analyzed; assuming the cosine load distribution around the contact area, constraining the radial displacement at the hole boundary, and using the contact element. To study the effect of failure criteria, Tsai-Wu and Yamada-Sun methods are applied on the characteristic curve. The results of the nonlinear analysis using the contact element showed good agrements with experimental data in both laminates made of uni-directional prepreg tapes and fabrics. In terms of failure criteria, Tsai-Wu method showed better agreement with experimental results than the one by Yamada-Sun laminate.

Cure Monitoring of Composite Laminates Using Fiber Optic Sensors (광섬유 센서를 이용한 복합재료 적층판의 성형 모니터링)

  • Gang, Hyeon-Gyu;Gang, Dong-Hun;Park, Hyeong-Jun;Hong, Chang-Seon;Kim, Cheon-Gon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.2
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    • pp.59-66
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    • 2002
  • In this paper, we present the simulataneous monitoring of the strain and temperature during cures f various composite laminates using fiber Bragg grating/extrinsic Fabry-Perot interferometric (FBG/EFPI) hybrid sensors. Three types of graphite/epoxy composite were used : a undirectional laminate, a symmetric cross-ply laminate, and a fabric laminate. Two FBG/EFPI hybrid sensors were embedded in each laminate at different directions and different locations. We performed the real time monitoring of fabrication strains and temperatures at two points within the composite laminates during cure process in an autoclave. Throuhg these experiments, FBG/EFPI sensors proved to be an efficient choice for smart cure monitoring of composite structures.

Prediction of Fatigue Life for Hole-notched Weave CFRP Plate (평직 CFRP 홀 노치재의 피로 수명 예측)

  • Kim, Sang-Young;Kim, Yong-Seok;Kwon, Hee-Whan;Choi, Jung-Hun;Koo, Jae-Mean;Seok, Chang-Sung
    • Composites Research
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    • v.23 no.3
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    • pp.1-6
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    • 2010
  • Recently, CFRP composite is more and more used in the various fields because of a higher specific modulus, chemical property and so on. Most products using CFRP composite are manufactured by construction of components. Various components are joined with those by bolts and pins. Holes for bolts and pins decrease strength and fatigue life of components, because those act as notch in structures. In this paper, we experimentally evaluated the fatigue life of hole-notched and unnotched weave CFRP plate. Then, we compared the two results and proposed an equation for prediction of fatigue life.

Progressive Failure Analysis of UD-Fabric Hybrid Laminated Composite Joints Considering Material Nonlinearity (재료비선형을 고려한 일방향-평직 혼합 적층 복합재 체결부의 점진적 파손해석)

  • 최정석;신소영;안현수;권진회
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2002.10a
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    • pp.79-82
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    • 2002
  • A finite element method based on the two-dimensional progressive failure analysis considering material nonlinearity is presented for characterizing the strength and failure of the unidirectional-fabric hybrid laminated composite joints under pin loading. The 8-node laminated shell element is incorporated in the updated Lagrangian formulation. Failure criteria including the Maximum Stress and Tsai-Wu are used in conjunction with the complete unloading stiffness degradation method. For the verification, joint tests are conducted for the specimens with two different ply-number ratios of UD composite to fabric composite. Although there are some differences depending on ply-number ratios, the finite element model using the maximum stress criterion considering nonlinear material behavior predicts the failure strength best.

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Prediction of engineering constants for plain and 8-hardness satin woven composites (평직 및 주자직 복합재료의 탄성계수 예측)

  • Byeon, Jun-Hyeong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.11
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    • pp.1757-1764
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    • 1997
  • The geometric and elastic models based on the unit cell have been proposed to predict the geometric characteristics and the engineering constants of plain and satin woven composites. In the geometric model, length and inclined angle of the yarn crimp and the fiber volume fraction of woven composites have been predicted. In the elastic model, the coordinate transformation has been utilized to transform the elastic constants of the yarn crimp to those of woven composites, and the effective elastic constants have been determined from the volume averaging of the constituent materials. Good correlations between the model predictions and the experimental results of carbon/epoxy and glass/epoxy woven composites have been observed. Based on the model, the effect of various geometric parameters and materials on the three-dimensional elastic properties of woven composites can be identified.

Evaluation of Residual Strength Under Impact Damage in Woven CFRP Composites (평직 CFRP 복합재료의 충격잔류강도 평가)

  • Choi, Jung-Hun;Kang, Min-Sung;Koo, Jae-Mean;Seok, Chang-Sung
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.6
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    • pp.654-663
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    • 2012
  • Damage induced by low velocity impact loading in aircraft composite is the form of failure which is frequently occurred in aircraft. As the consequences of impact loading in composite laminates, matrix cracking, delamination and eventually fiber breakage for higher impact energies can be occurred. Even when no visible impact damage is observed, damage can exist inside of composite laminates and carrying load of the composite laminates is considerably reduced. The objective of this study is to evaluate and predict residual strength behavior of composite laminates by impact loading and for this, tensile test after impact was carried out on composite laminates made of woven CFRP.

A Study on the Crack Growth Behavior and Fracture Criterion of Glass/Epoxy Composites (Glass/Epoxy 복합재료의 파괴조건 및 균열진전거동)

  • 김정규;김도식
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.16 no.9
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    • pp.1681-1690
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    • 1992
  • The effects of the stress ratio and the fiber orientation(0.deg./90.deg. and .+-.45.deg.) to the load direction on the fracture behavior of the glass/epoxy plain woven composites were studied. The tests were carried out using compact tension specimens under both static and fatigue loading. The values of $k_{a}$ obtained from the energy release rate are independent of notch depth(a/w=0.2~0.6) for the 0.deg./90.deg. specimens, but decreases with an increase in a/w for the .+-.45.deg. specimens. And $k_{q}$ has higher values than $k_{ASTM}$ has been evaluated by the ASTM E399 test procedure. It is shown in the relation between fatigue crack growth rate da/dN and stress intensity factor range .DELTA.K using modified shape correction factor that da/dN decreases with a decrease in stress ratio and is lower for .+-..deg. specimens than for 0.deg./90.deg. These phenomena can be explained by the crack deflection to the load direction.n.n.