• Title/Summary/Keyword: thick laminates

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Transverse Shear Deformation in the Cylindrical Bending of Laminated Plates (적층판의 원통형 굽힘에 대한 횡방향 전단병형)

  • 이수용;박정선
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.11
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    • pp.2696-2704
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    • 2000
  • This paper presents a new laminated plate theory for the cylindrical bending of laminated plated. The theory assumes that in plane displacements vary exponentially through plate thickness. Analytical solutions are derived for simply supported plates subjected to transverse loading. The accuracy of the present theory is examined for unsymmetric laminates, and the numerical results are compared with three-dimensional elasticity solutions of Pagano. The present theory predicts displacements and stresses for very thick plates very accurately. In particular, transverse shear stresses obtained form constitutive equations are predicted very accurately.

Through-thickness CTE and Void Content of Carbon Fabric Phenolic Composites with Respect to Compaction (압착에 따른 탄소직물 페놀 복합재의 두께방향 열팽창계수와 기공분율)

  • Kim, Jong-Woon;Kim, Hyong-Geun;Lee, Dai-Gil
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.192-197
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    • 2004
  • The anisotropy in coefficient of thermal expansion (CTE) between the in-plane and out-of-plane of 3-dimensional thick composite structures induces residual stresses and the large void content due to insufficient compaction of fabric composites, which results in low interlaminar strengths. In order to reduce the through thickness CTE and the void content, in this work, carbon fabric phenolic laminates were compacted by pressure generated by autoclave and a compressive jig, from which the through-thickness CTEs and the void contents were measured. From the measurement, it was found that the through-thickness CTE and the void content had different characteristics from ordinary composites due to gas produced during the cure reaction of phenolic resin.

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Stability and vibration analysis of composite plates using spline finite strips with higher-order shear deformation

  • Akhras, G.;Li, W.
    • Structural Engineering and Mechanics
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    • v.27 no.1
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    • pp.1-16
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    • 2007
  • In the present study, a spline finite strip with higher-order shear deformation is formulated for the stability and free vibration analysis of composite plates. The analysis is conducted based on Reddy's third-order shear deformation theory, Touratier's "Sine" model, Afaq's exponential model and Cho's higher-order zigzag laminate theory. Consequently, the shear correction coefficients are not required in the analysis, and an improved accuracy for thick laminates is achieved. The numerical results, based on different shear deformation theories, are presented in comparison with the three-dimensional elasticity solutions. The effects of length-to-thickness ratio, fibre orientation, and boundary conditions on the critical buckling loads and natural frequencies are investigated through numerical examples.

Thermal buckling and stability of laminated plates under non uniform temperature distribution

  • Widad Ibraheem Majeed;Ibtehal Abbas Sadiq
    • Steel and Composite Structures
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    • v.47 no.4
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    • pp.503-511
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    • 2023
  • Stability of laminated plate under thermal load varied linearly along thickness, is developed using a higher order displacement field which depend on a parameter "m", whose value is optimized to get results closest to three-dimension elasticity results. Hamilton, s principle is used to derive equations of motion for laminated plates. These equations are solved using Navier-type for simply supported boundary conditions to obtain non uniform critical thermal buckling and fundamental frequency under a ratio of this load. Many design parameters of cross ply and angle ply laminates such as, number of layers, aspect ratios and E1/E2 ratios for thick and thin plates are investigated. It is observed that linear and uniform distribution of temperature reduces plate frequency.

Evaluation and Application of T-Ray Nondestructive Characterization of FRP Composite Materials (FRP 복합재료의 T-Ray 비파괴특성 평가 및 적용)

  • Im, Kwang-Hee;Hsu, David K.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.30 no.5
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    • pp.429-436
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    • 2010
  • Recently, (terahertz ray) applications have emerged as one of the most promising new powerful nondestructive evaluation (NDE) techniques. In this study, a new T-ray time-domain spectroscopy system was utilized for detecting and evaluating layup effect and flaw in FRP composite laminates. Extensive experimental measurements in reflection and thru-transmission modes were made to map out the T-ray images. Especially this was demonstrated in thick GFRP laminates containing double saw slots. In carbon composites the penetration of terahertz waves is limited to some degree and the detection of flaws is strongly affected by the angle between the electric field(E-field) vector of the terahertz waves and the intervening fiber directions. The artificial defects investigated by terahertz waves were bonded foreign material, simulated disbond and delamination and mechanical impact damage. The effectiveness and limitations of terahertz radiation for the NDE of composites are discussed.

Critical Buckling Temperatures of Anisotropic Laminated Composite Plates considering a Higher-order Shear Deformation (고차전단변형을 고려한 비등방성 적층복합판의 임계좌굴온도)

  • Han, Seong Cheon;Yoon, Seok Ho;Chang, Suk Yoon
    • Journal of Korean Society of Steel Construction
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    • v.10 no.2 s.35
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    • pp.201-209
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    • 1998
  • The presence of elevated temperature can alter significantly the structural response of fibre-reinforced laminated composites. A thermal environment causes degradation in both strength and constitutive properties, particularly in the case of fibre-reinforced polymeric composites. Furthermore, associated thermal expansion, either alone or in combination with mechanically induced deformation, can result in buckling, large deflections, and excessively high stress levels. Consequently, it is often imperative to consider environmental effects in the analysis and design of laminated systems. Exact analytical solutions of higher-order shear deformation theory is developed to study the thermal buckling of cross-ply and antisymmetric angle-ply rectangular plates. The buckling behavior of moderately thick cross-ply and antisymmetric angle-ply laminates that are simply supported and subject to a uniform temperature rise is analyzed. Numerical results are presented for fiber-reinforced laminates and show the effects of ply orientation, number of layers, plate thickness, and aspects ratio on the critical buckling temperature and compared with those obtained using the classical and first-order shear deformation theory.

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Thermal Stress Analysis of Composite Beam through Dimension Reduction and Recovery Relation (차원축소와 복원관계를 통한 복합재료 보의 열응력 해석)

  • Jang, Jun Hwan;Ahn, Sang Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.5
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    • pp.381-387
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    • 2017
  • Fiber-reinforced composites not only have a direction of thermal expansion coefficient, but also inevitably suffer thermal stress effects due to the difference between the manufacturing process temperature and the actual use temperature. The damage caused by thermal stress is more prominent in the case of thick composite laminates, which are increasingly applied in the aerospace industry, and have a great influence on the mechanical function and fracture strength of the laminates. In this study, the dimensional reduction and thermal stress recovery theory of composite beam structure having high slenderness ratio is introduced and show the efficiency and accuracy of the thermal stress comparison results between the 3-D finite element model and the dimension reduction beam model. Efficient recovery analysis study will be introduced by reconstructing the thermal stress of the composite beam section applied to the thermal environment by constructing the dimensional reduction modeling and recovery relations.

The Properties of $Bi_2Mg_{2/3}Nb_{4/3}O_7$ Thin Films Deposited on Copper Clad Laminates For Embedded Capacitor (임베디드 커패시터의 응용을 위해 CCL 기판 위에 평가된 BMN 박막의 특성)

  • Kim, Hae-Won;Ahn, Jun-Ku;Ahn, Kyeong-Chan;Yoon, Soon-Gil
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2007.06a
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    • pp.45-45
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    • 2007
  • Capacitors among the embedded passive components are most widely studied because they are the major components in terms of size and number and hard to embed compared with resistors and inductors due to the more complicated structure. To fabricate a capacitor-embedded PCB for in-line process, it is essential to adopt a low temperature process (<$200^{\circ}C$). However, high dielectric materials such as ferroelectrics show a low permittivity and a high dielectric loss when they are processed at low temperatures. To solve these contradicting problems, we studied BMN materials as a candidate for dielectric capacitors. processed at PCB-compatible temperatures. The morphologies of BMN thin films were investigated by AFM and SEM equipment. The electric properties (C-F, I-V) of Pt/BMN/Cu/polymer were evaluated using an impedance analysis (HP 4194A) and semiconductor parameter analyzer (HP4156A). $Bi_2Mg_{2/3}Nb_{4/3}O_7$(BMN) thin films deposited on copper clad laminate substrates by sputtering system as a function of Ar/$O_2$ flow rate at room temperature showed smooth surface morphologies having root mean square roughness of approximately 5.0 nm. 200-nm-thick films deposited at RT exhibit a dielectric constant of 40, a capacitance density of approximately $150\;nF/cm^2$, and breakdown voltage above 6 V. The crystallinity of the BMN thin films was studied by TEM and XRD. BMN thin film capacitors are expected to be promising candidates as embedded capacitors for printed circuit board (PCB).

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Domain decomposition technique to simulate crack in nonlinear analysis of initially imperfect laminates

  • Ghannadpour, S. Amir M.;Karimi, Mona
    • Structural Engineering and Mechanics
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    • v.68 no.5
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    • pp.603-619
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    • 2018
  • In this research, an effective computational technique is carried out for nonlinear and post-buckling analyses of cracked imperfect composite plates. The laminated plates are assumed to be moderately thick so that the analysis can be carried out based on the first-order shear deformation theory. Geometric non-linearity is introduced in the way of von-Karman assumptions for the strain-displacement equations. The Ritz technique is applied using Legendre polynomials for the primary variable approximations. The crack is modeled by partitioning the entire domain of the plates into several sub-plates and therefore the plate decomposition technique is implemented in this research. The penalty technique is used for imposing the interface continuity between the sub-plates. Different out-of-plane essential boundary conditions such as clamp, simply support or free conditions will be assumed in this research by defining the relevant displacement functions. For in-plane boundary conditions, lateral expansions of the unloaded edges are completely free while the loaded edges are assumed to move straight but restricted to move laterally. With the formulation presented here, the plates can be subjected to biaxial compressive loads, therefore a sensitivity analysis is performed with respect to the applied load direction, along the parallel or perpendicular to the crack axis. The integrals of potential energy are numerically computed using Gauss-Lobatto quadrature formulas to get adequate accuracy. Then, the obtained non-linear system of equations is solved by the Newton-Raphson method. Finally, the results are presented to show the influence of crack length, various locations of crack, load direction, boundary conditions and different values of initial imperfection on nonlinear and post-buckling behavior of laminates.

Nonlocal bending, vibration and buckling of one-dimensional hexagonal quasicrystal layered nanoplates with imperfect interfaces

  • Haotian Wang;Junhong Guo
    • Structural Engineering and Mechanics
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    • v.89 no.6
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    • pp.557-570
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    • 2024
  • Due to interfacial ageing, chemical action and interfacial damage, the interface debonding may appear in the interfaces of composite laminates. Particularly, the laminates display a side-dependent effect at small scale. In this work, a three-dimensional (3D) and anisotropic thick nanoplate model is proposed to investigate the effects of imperfect interface and nonlocal parameter on the bending deformation, vibrational response and buckling stability of one-dimensional (1D) hexagonal quasicrystal (QC) layered nanoplates. By combining the linear spring model with the transferring matrix method, exact solutions of phonon and phason displacements, phonon and phason stresses of bending deformation, the natural frequencies of vibration and the critical buckling loads of 1D hexagonal QC layered nanoplates are derived with imperfect interfaces and nonlocal effects. Numerical examples are illustrated to demonstrate the effects of the imperfect interface parameter, aspect ratio, thickness, nonlocal parameter, and stacking sequence on the bending deformation, the vibrational response and the critical buckling load of 1D hexagonal QC layered nanoplate. The results indicate that both the interface debonding and nonlocal effect can reduce the stiffness and stability of layered nanoplates. Increasing thickness of QC coatings can enhance the stability of sandwich nanoplates with the perfect interfaces, while it can reduce first and then enhance the stability of sandwich nanoplates with the imperfect interfaces. The biaxial compression easily results in an instability of the QC layered nanoplates compared to uniaxial compression. QC material is suitable for surface layers in layered structures. The mechanical behavior of QC layered nanoplates can be optimized by imposing imperfect interfaces and controlling the stacking sequence artificially. The present solutions are helpful for the various numerical methods, thin nanoplate theories and the optimal design of QC nano-composites in engineering practice with interfacial debonding.