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  • Composite Materials  (9)
  • AIRCRAFT DESIGN, TESTING AND PERFORMANCE  (2)
  • 1
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    Experimental Verification of Computational Models for Laminated Composites (1999)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The objective of the research reported herein is to develop a progressive damage methodology capable of predicting the residual strength of continuous fiber-reinforced, laminated, polymer matrix composites with through-penetration damage. The fracture behavior of center-notch tension panels with thin crack-like slits was studied. Since fibers are the major load-carrying constituent in polymer matrix composites, predicting the residual strength of a laminate requires a criterion for fiber fracture. The effects on fiber strain due to other damage mechanisms such as matrix cracking and delaminations must also be modeled. Therefore, the research herein examines the damage mechanisms involved in translaminate fracture and identifies the toughening mechanisms responsible for damage growth resistance in brittle epoxy matrix systems. The mechanics of matrix cracking and fiber fracture are discussed as is the mathematical framework for the progressive damage model developed by the authors. The progressive damage analysis algorithms have been implemented into a general purpose finite element code developed by NASA, the Computational Structural Mechanics Testbed (COMET). Damage growth is numerically simulated and the analytical residual strength predictions are compared to experimental results for a variety of notched panel configurations and materials systems.
    Keywords: Composite Materials
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    NASA TECHNICAL REPORTS
  • 2
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    A Damage-Dependent Finite Element Analysis for Fiber-Reinforced Composite Laminates (1998)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: A progressive damage methodology has been developed to predict damage growth and residual strength of fiber-reinforced composite structure with through penetrations such as a slit. The methodology consists of a damage-dependent constitutive relationship based on continuum damage mechanics. Damage is modeled using volume averaged strain-like quantities known as internal state variables and is represented in the equilibrium equations as damage induced force vectors instead of the usual degradation and modification of the global stiffness matrix.
    Keywords: Composite Materials
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    NASA TECHNICAL REPORTS
  • 3
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    Recent fracture mechanics results from NASA research related to the aging commercial transport fleet (1991)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: NASA is conducting the Airframe Structural Integrity Program in support of the aging commercial transport fleet. This interdisciplinary program is being worked in cooperation with the U.S. airframe manufacturers, airline operators, and the FAA. Advanced analysis methods are under development to predict the fatigue crack growth in complex built-up shell structures. Innovative nondestructive examination technologies are also under development to provide large area inspection capability to detect corrosion, disbonds, and fatigue cracks. Recent fracture mechanics results applicable to predicting the growth of cracks initiating at the rivets of fuselage splice joints are reviewed.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AGARD, Fatigue Management; 6 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Evaluation of the concept of pressure proof testing fuselage structures (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The FAA and NASA have recently completed independent technical evaluations of the concept of pressure proof testing the fuselage of commercial transport airplanes. The results of these evaluations are summarized. The objectives of the evaluations were to establish the potential benefit of the pressure proof test, to quantify the most desirable proof test pressure, and to quantify the required proof test interval. The focus of the evaluations was on multiple-site cracks extending from adjacent rivet holes of a typical fuselage longitudinal lap splice joint. The FAA and NASA do not support pressure proof testing the fuselage of aging commercial transport aircraft. The argument against proof testing is as follows: (1) a single proof test does not insure an indefinite life; therefore, the proof test must be repeated at regular intervals; (2) for a proof factor of 1.33, the required proof test interval must be below 300 flights to account for uncertainties in the evaluation; (3) conducting the proof test at a proof factor of 1.5 would considerably exceed the fuselage design limit load; therefore, it is not consistent with accepted safe practices; and (4) better safety can be assured by implementing enhanced nondestructive inspection requirements, and adequate reliability can be achieved by an inspection interval several times longer than the proof test interval.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: DOT/FAA/CT-TN91/31
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    A Progressive Damage Methodology for Residual Strength Predictions of Notched Composite Panels (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The translaminate fracture behavior of carbon/epoxy structural laminates with through-penetration notches was investigated to develop a residual strength prediction methodology for composite structures. An experimental characterization of several composite materials systems revealed a fracture resistance behavior that was very similar to the R-curve behavior exhibited by ductile metals. Fractographic examinations led to the postulate that the damage growth resistance was primarily due to fractured fibers in the principal load-carrying plies being bridged by intact fibers of the adjacent plies. The load transfer associated with this bridging mechanism suggests that a progressive damage analysis methodology will be appropriate for predicting the residual strength of laminates with through-penetration notches. A progressive damage methodology developed by the authors was used to predict the initiation and growth of matrix cracks and fiber fracture. Most of the residual strength predictions for different panel widths, notch lengths, and material systems were within about 10% of the experimental failure loads.
    Keywords: Composite Materials
    Type: NASA/TM-1998-207646 , L-17729 , NAS 1.15:207646
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    NASA TECHNICAL REPORTS
  • 6
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    An Assessment of the State-of-the-Art in the Design and Manufacturing of Large Composite Structures for Aerospace Vehicles (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The results of an assessment of the state-of-the-art in the design and manufacturing of large composite structures are described. The focus of the assessment is on the use of polymeric matrix composite materials for large airframe structural components. such as those in commercial and military aircraft and space transportation vehicles. Applications of composite materials for large commercial transport aircraft, general aviation aircraft, rotorcraft, military aircraft. and unmanned rocket launch vehicles are reviewed. The results of the assessment of the state-of-the-art include a summary of lessons learned, examples of current practice, and an assessment of advanced technologies under development. The results of the assessment conclude with an evaluation of the future technology challenges associated with applications of composite materials to the primary structures of commercial transport aircraft and advanced space transportation vehicles.
    Keywords: Composite Materials
    Type: NASA/TM-2001-210844 , L-18070 , NAS 1.15:210844
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    NASA TECHNICAL REPORTS
  • 7
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    A Revolution in the Making: Advances in Materials That May Transform Future Exploration Infrastructures and Missions (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NASA Strategic Plan identifies the long-term goal to provide safe and affordable space access, orbital transfer, and interplanetary transportation capabilities to enable research, human exploration, and the commercial development of space; and to conduct human and robotic missions to planets and other bodies in our solar system. Numerous scientific and engineering breakthroughs will be required to develop the technology necessary to achieve this goal. Critical technologies include advanced vehicle primary and secondary structure, radiation protection, propulsion and power systems, fuel storage, electronics and devices, sensors and science instruments, and medical diagnostics and treatment. Advanced materials with revolutionary new capabilities are an essential element of each of these technologies. This paper discusses those materials best suited for aerospace vehicle structure and highlights the enormous potential of one revolutionary new material, carbon nanotubes.
    Keywords: Composite Materials
    Type: AIAA Paper 2001-4679 , AIAA Space 2001 Conference and Exposition; Aug 28, 2001 - Aug 30, 2001; Albuquerque, NM; United States
    Format: text
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  • 8
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    Mechanics of Textile Composites Conference (1995)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This document is a compilation of papers presented at the Mechanics of Textile Composites Conference in Hampton, Virginia, December 6-8, 1994. This conference was the culmination of a 3-year program that was initiated by NASA late in 1990 to develop mechanics of textile composites in support of the NASA Advanced Composites Technology Program (ACT). The goal of the program was to develop mathematical models of textile preform materials and test methods to facilitate structural analysis and design. Participants in the program were from NASA, academia, and industry.
    Keywords: Composite Materials
    Type: NASA-CP-3311-Pt-1 , L-17532A , NAS 1.55:3311-Pt-1 , Mechanics of Textile Composites Conference; Dec 06, 1994 - Dec 08, 1994; Hampton, VA; United States
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  • 9
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    A Survey of Emerging Materials for Revolutionary Aerospace Vehicle Structures and Propulsion Systems (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The NASA Strategic Plan identifies the long-term goal of providing safe and affordable space access, orbital transfer, and interplanetary transportation capabilities to enable scientific research, human, and robotic exploration, and the commercial development of space. Numerous scientific and engineering breakthroughs will be required to develop the technology required to achieve this goal. Critical technologies include advanced vehicle primary and secondary structure, radiation protection, propulsion and power systems, fuel storage, electronics and devices, sensors and science instruments, and medical diagnostics and treatment. Advanced materials with revolutionary new capabilities are an essential element of each of these technologies. A survey of emerging materials with applications to aerospace vehicle structures and propulsion systems was conducted to assist in long-term Agency mission planning. The comprehensive survey identified materials already under development that could be available in 5 to 10 years and those that are still in the early research phase and may not be available for another 20 to 30 years. The survey includes typical properties, a description of the material and processing methods, the current development status, and the critical issues that must be overcome to achieve commercial viability.
    Keywords: Composite Materials
    Type: NASA/TM-2002-211664 , L-18188 , NAS 1.15:211664
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    NASA TECHNICAL REPORTS
  • 10
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    Progressive Damage Analysis of Laminated Composite (PDALC) (A Computational Model Implemented in the NASA COMET Finite Element Code) (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A method for analysis of progressive failure in the Computational Structural Mechanics Testbed is presented in this report. The relationship employed in this analysis describes the matrix crack damage and fiber fracture via kinematics-based volume-averaged damage variables. Damage accumulation during monotonic and cyclic loads is predicted by damage evolution laws for tensile load conditions. The implementation of this damage model required the development of two testbed processors. While this report concentrates on the theory and usage of these processors, a complete listing of all testbed processors and inputs that are required for this analysis are included. Sample calculations for laminates subjected to monotonic and cyclic loads were performed to illustrate the damage accumulation, stress redistribution, and changes to the global response that occurs during the loading history. Residual strength predictions made with this information compared favorably with experimental measurements.
    Keywords: Composite Materials
    Type: NASA/TM-1998-208718 , L-17761 , NAS 1.15:208718
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