Testing and Analysis of Composite Skin/Stringer Debonding Under Multi-Axial Loading PDF Download
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Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721014392
Category :
Languages : en
Pages : 60
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Book Description
Damage mechanisms in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out- of-plane) loading conditions were examined. Specimens consisted of a tapered composite flange bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending . For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. The observations showed that, for all three load cases, failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from the skin. A two-dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, principal stresses exceeded the transverse strength of the material in the flange area. Additionally, delaminations of various lengths were simulated in two locations where delaminations were observed. The analyses showed that unstable delamination propagation is likely to occur in one location at the loads corresponding to matrix ply crack initiation for all three load cases.Krueger, Ronald and Cvitkovich, Michael K. and OBrien, T. Kevin and Minguet, Pierre J.Langley Research CenterCOMPOSITE MATERIALS; STRINGERS; AXIAL LOADS; SKIN (STRUCTURAL MEMBER); DAMAGE; TESTS; DEBONDING (MATERIALS); FINITE ELEMENT METHOD; FRACTURE MECHANICS; FLANGES; PLANE STRAIN; TWO DIMENSIONAL MODELS; COMPOSITE STRUCTURES; STRESS ANALYSIS
Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781721014392
Category :
Languages : en
Pages : 60
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Book Description
Damage mechanisms in composite bonded skin/stringer constructions under uniaxial and biaxial (in-plane/out- of-plane) loading conditions were examined. Specimens consisted of a tapered composite flange bonded onto a composite skin. Tests were performed under monotonic loading conditions in tension, three-point bending, and combined tension/bending . For combined tension/bending testing, a unique servohydraulic load frame was used that was capable of applying both in-plane tension and out-of-plane bending loads simultaneously. Specimen edges were examined on the microscope to document the damage occurrence and to identify typical damage patterns. The observations showed that, for all three load cases, failure initiated in the flange, near the flange tip, causing the flange to almost fully debond from the skin. A two-dimensional plane-strain finite element model was developed to analyze the different test cases using a geometrically nonlinear solution. For all three loading conditions, principal stresses exceeded the transverse strength of the material in the flange area. Additionally, delaminations of various lengths were simulated in two locations where delaminations were observed. The analyses showed that unstable delamination propagation is likely to occur in one location at the loads corresponding to matrix ply crack initiation for all three load cases.Krueger, Ronald and Cvitkovich, Michael K. and OBrien, T. Kevin and Minguet, Pierre J.Langley Research CenterCOMPOSITE MATERIALS; STRINGERS; AXIAL LOADS; SKIN (STRUCTURAL MEMBER); DAMAGE; TESTS; DEBONDING (MATERIALS); FINITE ELEMENT METHOD; FRACTURE MECHANICS; FLANGES; PLANE STRAIN; TWO DIMENSIONAL MODELS; COMPOSITE STRUCTURES; STRESS ANALYSIS
Author: United States. National Aeronautics and Space Administration
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author:
Publisher:
ISBN:
Category : Aerodynamic measurements
Languages : en
Pages : 62
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Author: Ronald Krueger
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 40
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Author: C. T. Sun
Publisher: CRC Press
ISBN: 0849315018
Category : Technology & Engineering
Languages : en
Pages : 1685
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Author: Peter Grant
Publisher: ASTM International
ISBN: 0803128622
Category : Composite construction
Languages : en
Pages : 557
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Book Description
The objective of the May 1999 symposium from which these 29 papers were drawn was to bring together practitioners and theoreticians in the composite structural mechanics field to better understand the needs and limitations each group works with. Papers are organized under seven general headings: str
Author: Srinivasan Sridharan
Publisher: Elsevier
ISBN: 1845694821
Category : Technology & Engineering
Languages : en
Pages : 787
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Book Description
Given such advantages as low weight compared to strength and toughness, laminated composites are now used in a wide range of applications. Their increasing use has underlined the need to understand their principal mode of failure, delamination. This important book reviews key research in understanding and preventing delamination.The first part of the book reviews general issues such as the role of fracture mechanics in understanding delamination, design issues and ways of testing delamination resistance. Part two describes techniques for detecting and characterising delamination such as piezoelectric sensors, the use of lamb waves and acoustic emission techniques. The next two sections of the book discuss ways of studying and modelling delamination behaviour. The final part of the book reviews research on delamination behaviour in particular conditions such as shell and sandwich structures, z-pin bridging and resin bonding.With its distinguished editor and international team of contributors, Delamination behaviour of composites is a standard reference for all those researching laminated composites and using them in such diverse applications as microelectronics, aerospace, marine, automotive and civil engineering. - Reviews the role of fracture mechanics in understanding delamination, design issues and ways of testing delamination resistance - Discuss ways of studying and modelling delamination behaviour - A standard reference for all those researching laminated composites
Author: TK. O'Brien
Publisher:
ISBN:
Category : Composite construction
Languages : en
Pages : 24
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Three simple procedures were developed to determine strain energy release rates, G, in composite skin/stringer specimens for various combinations of uniaxial and biaxial (in-plane/out-of-plane) loading conditions. These procedures may be used for parametric design studies in such a way that only a few finite-element computations will be necessary for a study of many load combinations. The results were compared with mixed-mode strain energy release rates calculated directly from nonlinear two-dimensional plane-strain finite-element analyses using the virtual crack closure technique. The first procedure involved solving three unknown parameters needed to determine the energy release rates. Good agreement was obtained when the external loads were used in the expression derived. This superposition technique, however, is applicable only if the structure exhibits a linear load/deflection behavior. Consequently, a second modified technique was derived which was applicable in the case of nonlinear load/deformation behavior. The technique, however, involved calculating six unknown parameters from a set of six simultaneous linear equations with data from six nonlinear analyses to determine the energy release rates. This procedure was not time efficient, and hence, less appealing.
Author: Ronald Krueger
Publisher:
ISBN:
Category : Composite materials
Languages : en
Pages : 74
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A shell/3D modeling technique was developed for which a local solid finite element model is used only in the immediate vicinity of the delamination front. The goal was to combine the accuracy of the full three-dimensional solution with the computational efficiency of a shell finite element model. Multi-point constraints provided a kinematically compatible interface between the local 3D model and the global structural model which has been meshed with shell finite elements. Double Camtilever Beam, End Notched Flexure, and Single Leg Bending specimens were analyzed first using full 3D finite element models to obtain reference solutions. Mixed mode strain energy release rate distributions were computed using the virtual crack closure technique. The analyses were repeated using the shell/3D technique to study the feasibility for pure mode I, mode II and mixed mode I/II cases. Specimens with a unidirectional layup and with a multidirectional layup were simulated. For a local 3D model, extending to a minimum of about three specimen thicknesses on either side of the delamination front, the results were in good agreement with mixed mode strain energy release rates obtained from computations where the entire specimen had been modeled with solid elements. For large built-up composite structures the shell/3D modeling technique offers a great potential for reducing the model size, since only a relatively small section in the vicinity of the delamination front needs to be modeled with solid elements.
Author:
Publisher:
ISBN:
Category : Astronautics
Languages : en
Pages : 182
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