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  • 1
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    Linear and non-linear failure analysis of composite laminates with transverse shear (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: A finite element computational procedure has been developed to find linear and nonlinear (von Karman) first-ply failure loads of composite laminates subjected to in-plane and transverse loads. The FEM is based on first-order shear deformation theory and several phenomenological failure criteria. It is found that the failure loads predicted by various failure criteria differ from one another by a maximum of 35 percent in the case of linear loads and 50 percent in the case of nonlinear loads; the failure locations differ from each other in a random way. It is demonstrated that the difference between the linear and nonlinear failure loads is large in the case of transversely loaded simply supported laminates and thin plates. The difference is found to be quite small in the case of in-plane (tensile) loading and thick laminates.
    Keywords: STRUCTURAL MECHANICS
    Type: Composites Science and Technology (ISSN 0266-3538); 44; 3 19
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  • 2
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    Three-dimensional finite element progressive failure analysis of composite laminates under axial extension (1993)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A three-dimensional (3D) progressive failure algorithm is developed, where the layerwise laminate theory (LWLT) of Reddy is used for kinematic description. The finite element model based on the layerwise theory predicts both inplane and interlaminar stresses with the same accuracy as that of a conventional 3D finite element model and provides a convenient format for modeling the 3D stress fields in composite laminates. A parametric study is conducted to investigate the effect of out-of-plane material properties, 3D stiffness reduction methods, and boundary conditions on the failure loads and strains of a composite laminate under axial extension. The results indicate that different parameters have a different degree of influence on the failure loads and strains. The predictive ability of various phenomenological failure criteria is evaluated in the light of experimental results available in the literature, and the predictions of the LWLT are compared with those of the first-order shear deformation theory. It is concluded that a 3D stress analysis is necessary to predict accurately the failure behavior of composite laminates.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Composites Technology & Research (ISSN 0885-6804); 15; 2; p. 73-87.
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  • 3
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    Mixed-mode fracture in unidirectional graphite epoxy composite laminates with central notch (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Mixed-mode matrix fracture in central notched off-axis unidirectional composite laminates was investigated. A limited number of unidirectional tensile type specimens with a central, horizontal, notch were tested. Crack initiation and propagation were examined under various local stress fields that were controlled by fiber orientations. The tested specimens were simulated using a two dimensional finite element method with constant strain loading. The strain energy release rates along the crack were evaluated via crack closure technique. The variation of critical strain energy rates with off-axis angle was studied. The results from single (one-sided) and double (two-sided) crack simulations were presented and compared.
    Keywords: STRUCTURAL MECHANICS
    Type: Journal of Reinforced Plastics and Composites (ISSN 0731-6844); 11; 324-338
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  • 4
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    On mixed and displacement finite element models of a refined shear deformation theory for laminated anisotropic plates (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An improved plate theory that accounts for the transverse shear deformation is presented, and mixed and displacement finite element models of the theory are developed. The theory is based on an assumed displacement field in which the inplane displacements are expanded in terms of the thickness coordinate up to the cubic term and the transverse deflection is assumed to be independent of the thickness coordinate. The governing equations of motion for the theory are derived from the Hamilton's principle. The theory eliminates the need for shear correction factors because the transverse shear stresses are represented parabolically. A mixed finite element model that uses independent approximations of the displacements and moments, and a displacement model that uses only displacements as degrees of freedom are developed. A comparison of the numerical results for bending with the exact solutions of the new theory and the three-dimensional elasticity theory shows that the present theory (and hence the finite element models) is more accurate than other plate-theories of the same order.
    Keywords: STRUCTURAL MECHANICS
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  • 5
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    A higher order theory of laminated composite cylindrical shells (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new higher order theory has been proposed for the analysis of composite cylindrical shells. The formulation allows for arbitrary variation of inplane displacements. Governing equations are presented in the form of a hierarchy of sets of partial differential equations. Each set describes the shell behavior to a certain degree of approximation. The natural frequencies of simply-supported isotropic and laminated shells and stresses in a ring loaded composite shell have been determined to various orders of approximation and compared with three dimensional solutions. These numerical studies indicate the improvements achievable in estimating the natural frequencies and the interlaminar shear stresses in laminated composite cylinders.
    Keywords: STRUCTURAL MECHANICS
    Type: Aeronautical Society of India, Journal (ISSN 0001-9267); 38; 161-171
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  • 6
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    Nonlinear analysis of laminated shells including transverse shear strains (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Numerical results obtained using a doubly curved, shear deformable shell element are presented for geometrically nonlinear analysis of laminated composite shells. The element is based on an extension of Sanders' shell theory and accounts for the von Karman strains and transverse shear strains. The sample numerical results presented here for the geometrically nonlinear analysis of laminated composite shells should serve as references for future investigations.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 440
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  • 7
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    Analysis of laminated composite shells using a degenerated 3-D element (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A special three-dimensional element based on the total Lagrangian description of the motion of a layered anisotropic composite medium is developed, validated and employed to analyze laminated anisotropic composite shells. The element contains the following features: geometric nonlinearity, dynamic (transient) behavior and arbitrary lamination scheme and lamina properties. Numerical results of nonlinear bending, natural vibration, and transient response are presented to illustrate the capabilities of the element.
    Keywords: STRUCTURAL MECHANICS
    Type: International Journal for Numerical Methods in Engineering (ISSN 0029-5981); 20; 1991-200
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  • 8
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    On computational schemes for global-local stress analysis (1989)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: An overview is given of global-local stress analysis methods and associated difficulties and recommendations for future research. The phrase global-local analysis is understood to be an analysis in which some parts of the domain or structure are identified, for reasons of accurate determination of stresses and displacements or for more refined analysis than in the remaining parts. The parts of refined analysis are termed local and the remaining parts are called global. Typically local regions are small in size compared to global regions, while the computational effort can be larger in local regions than in global regions.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Langley Research Center, Computational Methods for Structural Mechanics and Dynamics, Part 1; p 123-134
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  • 9
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    Stall flutter analysis of propfans (1988)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Three semi-empirical aerodynamic stall models are compared with respect to their lift and moment hysteresis loop prediction, limit cycle behavior, easy implementation, and feasibility in developing the parameters required for stall flutter prediction of advanced turbines. For the comparison of aeroelastic response prediction including stall, a typical section model and a plate structural model are considered. The response analysis includes both plunging and pitching motions of the blades. In model A, a correction of the angle of attack is applied when the angle of attack exceeds the static stall angle. In model B, a synthesis procedure is used for angles of attack above static stall angles, and the time history effects are accounted for through the Wagner function.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA, Lewis Research Center, Lewis Structures Technology, 1988. Volume 1: Structural Dynamics; p 405-419
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  • 10
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    A three-dimensional nonlinear analysis of cross-ply rectangular composite plates (1984)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The results of a three-dimensional, geometrically nonlinear, finite-element analysis of the bending of cross-ply laminated anisotropic composite plates are presented. Individual laminae are assumed to be homogeneous, orthotropic and linearly elastic. A fully three-dimensional isoparametric finite element with eight nodes (i.e. linear element) and 24 degrees of freedom (three displacement components per node) is used to model the laminated plate. The finite element results of the linear analysis are found to agree very well with the exact solutions of cross-ply laminated rectangular plates under sinusoidal loading. The finite element results of the three-dimensional, geometrically nonlinear analysis are compared with those obtained by using a shear deformable, geometrically nonlinear, plate theory. It is found that the deflections predicted by the shear deformable plate theory are in fair agreement with those predicted by three-dimensional elasticity theory; however stresses were found to be not in good agreement.
    Keywords: STRUCTURAL MECHANICS
    Type: Computers and Structures (ISSN 0045-7949); 18; 2, 19; 1984
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