• Title/Summary/Keyword: Composite laminates

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A Study on Characterization for Stacking Fault Evaluation of CFRP Composite Laminates Using an EMAT Ultrasonics (전자기 초음파를 이용한 CFRP 복합적층판의 적층배향 특성평가에 관한 연구)

  • Im, Kwang-Hee;Na, Seung-Woo;Kim, Ji-Hoon;Lee, Chang-Ro;Hsu, David K.;Yang, In-Young
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.2
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    • pp.83-92
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    • 2005
  • An electromagnetic acoustic transducer (EMAT) is a unique probe that does not require a couplant or gel and also can usually generate or detect an ultrasonic wave into specimens across a small gap. It, therefore can be applied in a noncontact mode with a high degree of reproducibility. Especially stiffness of composites depends on layup sequence of CFRP(carbon fiber reinforced plastics) laminates. It is very important to evaluate the layup errors in prepreg laminates. A nondestructive technique can therefore serve as a useful measurement for detecting layup errors. This shear wave for detecting the presence of the errors is very sensitive. A decomposition model has been used in the interpretation and prediction of test results. Test results have been com pared with model data. It is found that the high probability shows between tests and the model utilized in characterizing cured layups of the laminates. Also a C-scan method was used for detecting layup of the laminates because of extracting fiber orientation information from the ultrasonic reflection caused by structural imperfections in the laminates. Therefore, it was found that interface C-scan images show the fiber orientation information by using two-dimensional fast Fourier transform (2-D FFT).

Study on the Damage Characteristics Under the High-Velocity Impact of Composite Laminates Using Various Sensor Signals (다양한 센서 신호를 이용한 복합적층판의 고속충격 손상 특성 연구)

  • Cho, Sang-Gyu;Kim, In-Gul;Lee, Seok-Je;You, Won-Young
    • Composites Research
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    • v.24 no.6
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    • pp.49-55
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    • 2011
  • The use of advanced composite materials in main structures of military and civil aircraft has been increased rapidly because of their considerable metals in high specific strength and stiffness. However, the mechanical properties of composite materials may severely degrade in the presence of damage. Especially, the high-velocity impact such as a hailstorm, and a small piece of tire or stone during high taxing, can cause considerable damage to the structures and sub-system in spite of a very small mass. However, it is not easy to detect the damage in composite plates using a single sensor or any conventional methods. In this paper, the PVDF sensors and AE sensors were used for monitoring high-velocity impact damage initiation and propagation in composite laminates. The WT(wavelet transform) is used to decompose the sensor signals. In the PVDF sensor and AE sensor signal analysis, amounts of high-frequency signals are increased when the impact energy is increased. PVDF sensor and AE sensor signal appeared similar results. This study shows how various sensing techniques can be used to characterize high-velocity impact damage of advanced composite laminates.

Free vibration analysis of stiffened laminated plates using layered finite element method

  • Guo, Meiwen;Harik, Issam E.;Ren, Wei-Xin
    • Structural Engineering and Mechanics
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    • v.14 no.3
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    • pp.245-262
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    • 2002
  • The free vibration analysis of stiffened laminated composite plates has been performed using the layered (zigzag) finite element method based on the first order shear deformation theory. The layers of the laminated plate is modeled using nine-node isoparametric degenerated flat shell element. The stiffeners are modeled as three-node isoparametric beam elements based on Timoshenko beam theory. Bilinear in-plane displacement constraints are used to maintain the inter-layer continuity. A special lumping technique is used in deriving the lumped mass matrices. The natural frequencies are extracted using the subspace iteration method. Numerical results are presented for unstiffened laminated plates, stiffened isotropic plates, stiffened symmetric angle-ply laminates, stiffened skew-symmetric angle-ply laminates and stiffened skew-symmetric cross-ply laminates. The effects of fiber orientations (ply angles), number of layers, stiffener depths and degrees of orthotropy are examined.

Cure simulation for a thick glass/epoxy laminate (유리섬유 강화 후판 복합재료의 경화공정 해석)

  • 오제훈;이대길
    • Proceedings of the Korean Society For Composite Materials Conference
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    • 2000.04a
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    • pp.53-58
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    • 2000
  • During the curing process of thick glass/epoxy laminates, a substantial amount of temperature lag and overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites. Also, it requires a longer time for full and uniform consolidation. In this work, temperature, degree of cure and consolidation of a 20mm thick unidirectional glass/epoxy laminate were investigated using an experiment and a 3-dimentional numerical analysis considering the exothermic reaction. From the experimental and numerical results, it was found that the experimentally obtained temperature profile agreed well with the numerical one and the cure cycle recommended by the prepreg manufacturer should be modified to prevent a temperature overshoot and to obtain full consolidation.

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Void Contents Evaluation of Composite Laminates by Ultrasonic Attenuation Measurements (초음파의 감쇠를 이용한 복합재료의 기공함량 평가)

  • 정현조
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.6
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    • pp.1535-1541
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    • 1994
  • The void content of carbon fiber reinforced composite laminates was determined by the ultrasonic nondestructive technique. The ultrasonic immersion, through-transmission method developed stresses the utilization of spectral analysis and frequency dependence of the attenuation due to porosity. The measured attenuation shows approximately linear behavior over the frequency range investigated. The linear relationship between the void content and the attenuation slop (d $\alpha$/df) is found to hold, but the constant of proportionality is quite different for samples with different pore morphology. The void volume fraction determined by the attenuation slope agreed very well with that obtained by the acid digestion analysis.

The Derivation of Generalized Quasi-Three Dimensional Displacement Field Equations for the Analysis of Composite Laminates (복합재료 적층판의 해석을 위한 일반화 준 3차원 변위식의 도출)

  • 김택현
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.7 no.4
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    • pp.21-27
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    • 1998
  • In the case of existing in free-edge delaminations of composite laminates which are symmetry with respect to mid-plane in laminates also, in the case of asymmetry and anti-symmetry, the generalized quasi-three dimensional displacement field equations developed from quasi-three dimensional displacement field equations can be applied to solve above cases. We introduce three paramenters in this paper, which have not been used in quasi-three dimensional displacement field equations until now. To the laminate subjected to the axial extension strain $\varepsilon$0(C1) in $\chi$-direction, the bending deformation $\chi$$\chi$(C$_2$) around у-direction, the bending deformation w$\chi$(C$_4$) around z-direction and the twisting deformation $\chi$$\chi$y(C$_3$) around $\chi$-direction .The generalized quasi-three dimensional displacement field equations are able to be analyzed efectively.

Thermal Buckling of Thick Laminated Composite Plates under Uniform Temperature Distribution (균일분포 온도하의 두꺼운 복합 재료 적층판의 열적 좌굴 해석)

  • Lee, Young-Shin;Lee, Yeol-Wha;Yang, Myung-Seog;Park, Bock-Sun;Lee, Jong-Soo
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.7 s.94
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    • pp.1686-1699
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    • 1993
  • In this paper, the thermal buckling of thick composite angle-ply laminates subject to uniform temperature distribution is studied. For the plates of 4-edges simply supported condition and those of 4-edges clamped condition, the critical buckling temperatue is derived, using tile finite element method based on the shear deformation theory. The effects of lamination angle, layer number, laminate thickness, plate aspect ratio and boundary constraints upon the critical buckling temperature are presented.

Statistical Properties for Tensile strength of Composite Materials Patched with AFRP on 2024-T3 Aluminum Alloy plate (Al 2024-T3 판에 AFRP를 접착한 복합재료의 인장강도에 대한 통계적 특성)

  • Yun, Han-Gi;An, Won-Gi;Heo, Seon-Cheol
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.7 s.178
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    • pp.1810-1816
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    • 2000
  • A hybrid composite APAL(Aramid Patched Aluminum alloy) , consisting of Al 2024-T3 aluminum alloy plate sandwiched between two aramid/epoxy laminates, was developed. The characteristics of tensile s trength were investigated and statistical properties of tensile strength were studied in terms of Weibull distribution probability with number of AFRP laminates. The tensile strength of APAL was inproportional to number of AFRP laminates and followed the two-parametic Weibull distribution.

Low velocity impact characteristics on environmental variation of composite laminates used in the light rail transit (경량전철 복합 적층판의 환경변화에 대한 저속충격특성)

  • 김후식;김재훈;이영신;박병준;조정미
    • Proceedings of the KSR Conference
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    • 2002.10a
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    • pp.86-91
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    • 2002
  • Glass/phenolic composite laminates have been used in the field of non-flammable light rail transit and their applications have expanded more widely. Low velocity impact tests have been used to evalute the effect of temperature and acceleration aging on low velocity impact response of phenolic matrix composites reinforced with woven E-glass fabric. The damage of matrix cracking and delamination are suddenly reduced the compressive strength after impact. The damage area increases with increasing temperature and impact energy. UT C-scan is used to determine damage areas by impact loading. Therefore, all this observations indicate reduced impact damage resistance and damage tolerance of the laminates at elevated temperature.

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Combined effects of end-shortening strain, lateral pressure load and initial imperfection on ultimate strength of laminates: nonlinear plate theory

  • Ghannadpour, S.A.M.;Barvaj, A. Kurkaani
    • Steel and Composite Structures
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    • v.33 no.2
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    • pp.245-259
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    • 2019
  • The present study aims to investigate the ultimate strength and geometric nonlinear behavior of composite plates containing initial imperfection subjected to combined end-shortening strain and lateral pressure loading by using a semi-analytical method. In this study, the first order shear deformation plate theory is considered with the assumption of large deflections. Regarding in-plane boundary conditions, two adjacent edges of the laminates are completely held while the two others can move straightly. The formulations are based on the concept of the principle of minimum potential energy and Newton-Raphson technique is employed to solve the nonlinear set of algebraic equations. In addition, Hashin failure criteria are selected to predict the failures. Further, two distinct models are assumed to reduce the mechanical properties of the failure location, complete ply degradation model, and ply region degradation model. Degrading the material properties is assumed to be instantaneous. Finally, laminates having a wide range of thicknesses and initial geometric imperfections with different intensities of pressure load are analyzed and discuss how the ultimate strength of the plates changes.