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  • 1
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    A high-resolution, cloud-assimilating numerical weather prediction model for solar irradiance forecasting (2013)
    Elsevier
    Details
    Publication Date: 2013-06-01
    Print ISSN: 0038-092X
    Electronic ISSN: 1471-1257
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Published by Elsevier
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  • 2
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    Progressive damage and failure modeling in notched laminated fiber reinforced composites (2009)
    Springer
    Details
    Publication Date: 2009-07-09
    Print ISSN: 0376-9429
    Electronic ISSN: 1573-2673
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Springer
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  • 3
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    Wind energy variability and links to regional and synoptic scale weather (2018)
    Springer
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    Publication Date: 2018-08-31
    Print ISSN: 0930-7575
    Electronic ISSN: 1432-0894
    Topics: Geosciences , Physics
    Published by Springer
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  • 4
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    Simplified Shear Solution for Determination of the Shear Stress Distribution in a Composite Panel from the Applied Shear Resultant (2008)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The simplified shear solution method is presented for approximating the through-thickness shear stress distribution within a composite laminate or panel based on laminated beam theory. The method does not consider the solution of a particular boundary value problem; rather it requires only knowledge of the global shear loading, geometry, and material properties of the laminate or panel. It is thus analogous to lamination theory in that ply level stresses can be efficiently determined from global load resultants (as determined, for instance, by finite element analysis) at a given location in a structure and used to evaluate the margin of safety on a ply by ply basis. The simplified shear solution stress distribution is zero at free surfaces, continuous at ply boundaries, and integrates to the applied shear load. Comparisons to existing theories are made for a variety of laminates, and design examples are provided illustrating the use of the method for determining through-thickness shear stress margins in several types of composite panels and in the context of a finite element structural analysis.
    Keywords: Structural Mechanics
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  • 5
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    Stiffness, thermal expansion, and thermal bending formulation of stiffened, fiber-reinforced composite panels (1993)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A method is presented for formulating stiffness terms and thermal coefficients of stiffened, fiber-reinforced composite panels. The method is robust enough to handle panels with general cross sectional shapes, including those which are unsymmetric and/or unbalanced. Nonlinear, temperature and load dependent constitutive material data of each laminate are used to 'build-up' the stiffened panel membrane, bending, and membrane-bending coupling stiffness terms and thermal coefficients. New thermal coefficients are introduced to quantify panel response from through-the-thickness temperature gradients. A technique of implementing this capability with a single plane of shell finite elements using the MSC/NASTRAN analysis program (FEA) is revealed that provides accurate solutions of entire airframes or engines with coarsely meshed models. An example of a composite, hat-stiffened panel is included to demonstrate errors that occur when an unsymmetric panel is symmetrically formulated as traditionally done. The erroneous results and the correct ones produced from this method are compared to analysis from discretely meshed three-dimensional FEA.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 93-1569 , In: AIAA(ASME)ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pt. 4 (A93-33876 1; p. 2279-2290.
    Format: text
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  • 6
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    Computational Implementation of a Thermodynamically Based Work Potential Model For Progressive Microdamage and Transverse Cracking in Fiber-Reinforced Laminates (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A continuum-level, dual internal state variable, thermodynamically based, work potential model, Schapery Theory, is used capture the effects of two matrix damage mechanisms in a fiber-reinforced laminated composite: microdamage and transverse cracking. Matrix microdamage accrues primarily in the form of shear microcracks between the fibers of the composite. Whereas, larger transverse matrix cracks typically span the thickness of a lamina and run parallel to the fibers. Schapery Theory uses the energy potential required to advance structural changes, associated with the damage mechanisms, to govern damage growth through a set of internal state variables. These state variables are used to quantify the stiffness degradation resulting from damage growth. The transverse and shear stiffness of the lamina are related to the internal state variables through a set of measurable damage functions. Additionally, the damage variables for a given strain state can be calculated from a set of evolution equations. These evolution equations and damage functions are implemented into the finite element method and used to govern the constitutive response of the material points in the model. Additionally, an axial failure criterion is included in the model. The response of a center-notched, buffer strip-stiffened panel subjected to uniaxial tension is investigated and results are compared to experiment.
    Keywords: Structural Mechanics
    Type: NASA/TM-2012-217243 , AIAA Paper 2010-2815 , E-17999 , 51th Structures, Structural Dynamics, and Materials Conference; Apr 12, 2010 - Apr 15, 2010; Orlando, FL; United States
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  • 7
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    Micromechanics and Piezo Enhancements of HyperSizer (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: The commercial HyperSizer aerospace-composite-material-structure-sizing software has been enhanced by incorporating capabilities for representing coupled thermal, piezoelectric, and piezomagnetic effects on the levels of plies, laminates, and stiffened panels. This enhancement is based on a formulation similar to that of the pre-existing HyperSizer capability for representing thermal effects. As a result of this enhancement, the electric and/or magnetic response of a material or structure to a mechanical or thermal load, or its mechanical response to an applied electric or magnetic field can be predicted. In another major enhancement, a capability for representing micromechanical effects has been added by establishment of a linkage between HyperSizer and Glenn Research Center s Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC) computer program, which was described in several prior NASA Tech Briefs articles. The linkage enables Hyper- Sizer to localize to the fiber and matrix level rather than only to the ply level, making it possible to predict local failures and to predict properties of plies from those of the component fiber and matrix materials. Advanced graphical user interfaces and database structures have been developed to support the new HyperSizer micromechanics capabilities.
    Keywords: Man/System Technology and Life Support
    Type: LEW-17819-1 , NASA Tech Briefs, September 2006; 22
    Format: application/pdf
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  • 8
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    HITEMP Material and Structural Optimization Technology Transfer (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The feasibility of adding viscoelasticity and the Generalized Method of Cells (GMC) for micromechanical viscoelastic behavior into the commercial HyperSizer structural analysis and optimization code was investigated. The viscoelasticity methodology was developed in four steps. First, a simplified algorithm was devised to test the iterative time stepping method for simple one-dimensional multiple ply structures. Second, GMC code was made into a callable subroutine and incorporated into the one-dimensional code to test the accuracy and usability of the code. Third, the viscoelastic time-stepping and iterative scheme was incorporated into HyperSizer for homogeneous, isotropic viscoelastic materials. Finally, the GMC was included in a version of HyperSizer. MS Windows executable files implementing each of these steps is delivered with this report, as well as source code. The findings of this research are that both viscoelasticity and GMC are feasible and valuable additions to HyperSizer and that the door is open for more advanced nonlinear capability, such as viscoplasticity.
    Keywords: Composite Materials
    Type: NASA/CR-2001-211166 , E-13030 , NAS 1.26:211166
    Format: application/pdf
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  • 9
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    Efficient Design and Analysis of Lightweight Reinforced Core Sandwich and PRSEUS Structures (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Design, analysis, and sizing methods for two novel structural panel concepts have been developed and incorporated into the HyperSizer Structural Sizing Software. Reinforced Core Sandwich (RCS) panels consist of a foam core with reinforcing composite webs connecting composite facesheets. Boeing s Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panels use a pultruded unidirectional composite rod to provide axial stiffness along with integrated transverse frames and stitching. Both of these structural concepts are ovencured and have shown great promise applications in lightweight structures, but have suffered from the lack of efficient sizing capabilities similar to those that exist for honeycomb sandwich, foam sandwich, hat stiffened, and other, more traditional concepts. Now, with accurate design methods for RCS and PRSEUS panels available in HyperSizer, these concepts can be traded and used in designs as is done with the more traditional structural concepts. The methods developed to enable sizing of RCS and PRSEUS are outlined, as are results showing the validity and utility of the methods. Applications include several large NASA heavy lift launch vehicle structures.
    Keywords: Structural Mechanics
    Type: NASA/TM-2011-217198 , AIAA Paper-2911-1909 , E-17883 , E-17883-1 , Structures, Structural Dynamics, and Materials Conference; Apr 04, 2011 - Apr 07, 2011; Demver, CO; Oman
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  • 10
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    Structural analysis and sizing of stiffened, metal matrix composite panels for hypersonic vehicles (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The present method for strength and stability analyses of stiffened, fiber-reinforced composite panels to be used in hypersonic vehicle structures is of great generality, and can be linked with planar finite-element analysis (FEA). Nonlinear temperature and load-dependent material data for each laminate are used to 'build-up' the stiffened panel's membrane, bending, and membrane-bending coupling stiffness terms, as well as thermal coefficients. The resulting, FEA-solved thermomechanical forces and moments are used to calculate strain at any location in the panel; this allows an effective ply-by-ply orthotropic strength analysis to be conducted, together with orthotropic instability checks for each laminated segment of the cross-section.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 92-5015 , ; 11 p.|AIAA, International Aerospace Planes Conference; Dec 01, 1992 - Dec 04, 1992; Orlando, FL; United States
    Format: text
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