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  • 1
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    Evaluation of a Progressive Failure Analysis Methodology for Laminated Composite Structures (1997)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A progressive failure analysis methodology has been developed for predicting the nonlinear response and failure of laminated composite structures. The progressive failure analysis uses C plate and shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms. The progressive failure analysis model is implemented into a general purpose finite element code and can predict the damage and response of laminated composite structures from initial loading to final failure.
    Keywords: Composite Materials
    Type: AIAA Paper 97-1187 , AIAA/ASME/ASCE/AHS/ASC 38th Structures, Structural Dynamics and Materials Conference; Apr 07, 1997 - Apr 10, 1997; United States
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  • 2
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    Assumed--stress hybrid elements with drilling degrees of freedom for nonlinear analysis of composite structures (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: The goal of this research project is to develop assumed-stress hybrid elements with rotational degrees of freedom for analyzing composite structures. During the first year of the three-year activity, the effort was directed to further assess the AQ4 shell element and its extensions to buckling and free vibration problems. In addition, the development of a compatible 2-node beam element was to be accomplished. The extensions and new developments were implemented in the Computational Structural Mechanics Testbed COMET. An assessment was performed to verify the implementation and to assess the performance of these elements in terms of accuracy. During the second and third years, extensions to geometrically nonlinear problems were developed and tested. This effort involved working with the nonlinear solution strategy as well as the nonlinear formulation for the elements. This research has resulted in the development and implementation of two additional element processors (ES22 for the beam element and ES24 for the shell elements) in COMET. The software was developed using a SUN workstation and has been ported to the NASA Langley Convex named blackbird. Both element processors are now part of the baseline version of COMET.
    Keywords: Composite Materials
    Type: NASA-CR-201025 , NAS 1.26:201025
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  • 3
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    Finite Element Modeling of the Buckling Response of Sandwich Panels (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A comparative study of different modeling approaches for predicting sandwich panel buckling response is described. The study considers sandwich panels with anisotropic face sheets and a very thick core. Results from conventional analytical solutions for sandwich panel overall buckling and face-sheet-wrinkling type modes are compared with solutions obtained using different finite element modeling approaches. Finite element solutions are obtained using layered shell element models, with and without transverse shear flexibility, layered shell/solid element models, with shell elements for the face sheets and solid elements for the core, and sandwich models using a recently developed specialty sandwich element. Convergence characteristics of the shell/solid and sandwich element modeling approaches with respect to in-plane and through-the-thickness discretization, are demonstrated. Results of the study indicate that the specialty sandwich element provides an accurate and effective modeling approach for predicting both overall and localized sandwich panel buckling response. Furthermore, results indicate that anisotropy of the face sheets, along with the ratio of principle elastic moduli, affect the buckling response and these effects may not be represented accurately by analytical solutions. Modeling recommendations are also provided.
    Keywords: Composite Materials
    Type: AIAA Paper 2002-1517 , 43rd AIAA/ASME/ASCE Structures, Structural Dynamics and Materials Conference; Apr 22, 2002 - Apr 25, 2002; Denver, CO; United States
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  • 4
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    Comparison of Requirements for Composite Structures for Aircraft and Space Applications (2010)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper, the aircraft and space vehicle requirements for composite structures are compared. It is a valuable exercise to study composite structural design approaches used in the airframe industry, and to adopt methodology that is applicable for space vehicles. The missions, environments, analysis methods, analysis validation approaches, testing programs, build quantities, inspection, and maintenance procedures used by the airframe industry, in general, are not transferable to spaceflight hardware. Therefore, while the application of composite design approaches from other industries is appealing, many aspects cannot be directly utilized. Nevertheless, experiences and research for composite aircraft structures may be of use in unexpected arenas as space exploration technology develops, and so continued technology exchanges are encouraged.
    Keywords: Composite Materials
    Type: NF1676L-11560 , International Conference on Composites for the 21st Century: Current and Future Trends; Jan 04, 2011 - Jan 07, 2011; Bangalore; India
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  • 5
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    Factors Influencing Progressive Failure Analysis Predictions for Laminated Composite Structure (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model for use with a nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details are described in the present paper. Parametric studies for laminated composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented and to demonstrate their influence on progressive failure analysis predictions.
    Keywords: Composite Materials
    Type: 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 07, 2008 - Apr 10, 2008; Schaumburg, IL; United States
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  • 6
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    Optimal Design of Grid-Stiffened Composite Panels Using Global and Local Buckling Analysis (1996)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A design strategy for optimal design of composite grid-stiffened panels subjected to global and local buckling constraints is developed using a discrete optimizer. An improved smeared stiffener theory is used for the global buckling analysis. Local buckling of skin segments is assessed using a Rayleigh-Ritz method that accounts for material anisotropy and transverse shear flexibility. The local buckling of stiffener segments is also assessed. Design variables are the axial and transverse stiffener spacing, stiffener height and thickness, skin laminate, and stiffening configuration. The design optimization process is adapted to identify the lightest-weight stiffening configuration and pattern for grid stiffened composite panels given the overall panel dimensions, design in-plane loads, material properties, and boundary conditions of the grid-stiffened panel.
    Keywords: Composite Materials
    Type: NASA-TM-111453 , NAS 1.15:111453 , AIAA Paper 96-1581 , AIAA/ASME/ASCE/AHS/ASC 37th Structures, Structural Dynamics, and Materials Conference; Apr 15, 1996 - Apr 17, 1996; Salt Lake City, UT; United States
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  • 7
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    User-Defined Material Model for Progressive Failure Analysis (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: An overview of different types of composite material system architectures and a brief review of progressive failure material modeling methods used for structural analysis including failure initiation and material degradation are presented. Different failure initiation criteria and material degradation models are described that define progressive failure formulations. These progressive failure formulations are implemented in a user-defined material model (or UMAT) for use with the ABAQUS/Standard1 nonlinear finite element analysis tool. The failure initiation criteria include the maximum stress criteria, maximum strain criteria, the Tsai-Wu failure polynomial, and the Hashin criteria. The material degradation model is based on the ply-discounting approach where the local material constitutive coefficients are degraded. Applications and extensions of the progressive failure analysis material model address two-dimensional plate and shell finite elements and three-dimensional solid finite elements. Implementation details and use of the UMAT subroutine are described in the present paper. Parametric studies for composite structures are discussed to illustrate the features of the progressive failure modeling methods that have been implemented.
    Keywords: Composite Materials
    Type: NASA/CR-2006-214526
    Format: application/pdf
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