Delamination and stitch failure in stitched composite joints

Glaessgen, Edward H.; Raju, I. S.; Poe, C. C.

doi:10.2514/6.1999-1247

Cited by 11 publications

(11 citation statements)

References 22 publications

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“…Fractures mechnics analyses performed by Glaessgen et.al. focussed on the debonding of stitched composite structures [122][123][124]. Delamination buckling has been investigated as well using plate/shell models [56,[125][126][127][128][129].…”

Section: Applying the Virtual Crack Closure Technique To Analysis Witmentioning

confidence: 99%

Virtual crack closure technique: History, approach, and applications

Krueger

2004

Applied Mechanics Reviews

1,109

557

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 An overview of the virtual crack closure technique is presented. The approach used is discussed, the history summarized, and insight i n to its applications provided. Equations for two-dimensional quadrilateral elements with linear and quadratic shape functions are given. Formulae for applying the technique in conjuction with threedimensional solid elements as well as plate shell elements are also provided. Necessary modi cations for the use of the method with geometrically nonlinear nite element analysis and corrections required for elements at the crack tip with di erent lengths and widths are discussed. The problems associated with cracks or delaminations propagating between di erent materials are mentioned brie y, a s w ell as a strategy to minimize these problems. Due to an increased interest in using a fracture mechanics based approach to assess the damage tolerance of composite structures in the design phase and during certi cation, the engineering problems selected as examples and given as references focus on the application of the technique to components made of composite materials. • TECHNICAL MEMORANDUM. Scientific and technical findings that are preliminary or of specialized interest, e.g., quick release reports, working papers, and bibliographies that contain minimal annotation. Does not contain extensive analysis.• CONTRACTOR REPORT. Scientific and technical findings by NASA-sponsored contractors and grantees.• CONFERENCE PUBLICATIONS. Collected papers from scientific and technical conferences, symposia, seminars, or other meetings sponsored or cosponsored by NASA.• SPECIAL PUBLICATION. Scientific, technical, or historical information from NASA programs, projects, and missions, often concerned with subjects having substantial public interest.• TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientific and technical material pertinent to NASA's mission. propagating between different materials are mentioned briefly, as well as a strategy to minimize these problems.Due to an increased interest in using a fracture mechanics based approach to assess the damage tolerance of composite structures in the design phase and during certification, the engineering problems selected as examples and given as references focus on the application of the technique to components made of composite materials.

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Section: Applying the Virtual Crack Closure Technique To Analysis Witmentioning

confidence: 99%

Virtual crack closure technique: History, approach, and applications

Krueger

2004

Applied Mechanics Reviews

1,109

557

View full text Add to dashboard Cite

show abstract

“…The debond initially grew rather uniformly across the specimen, but once the debond length reached approximately 2 cm from either end, further growth was dominated by growth along the edge of the specimen. A previously conducted analysis of this joint showed that the G-values at the edge of the specimen are elevated suggesting this possibility [7,8]. The debonding along the edges continued to grow until the entire edge was debonded.…”

Section: Debonding Of Stitched Composite Jointsmentioning

confidence: 87%

Debonding of Stitched Composite Joints under Static and Fatigue Loading

Reeder

Glaessgen

2004

Journal of Reinforced Plastics and Composites

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An experimental study was conducted to examine the effects of stitches on the static and fatigue failure of two different single lap joint configurations. To monitor damage growth, X-rays were taken periodically during the fatigue tests. The study showed that a 21/2 fold increase in static strength due to stitching. A similar increase was found in fatigue strength for a given fatigue life. Additionally, stitching significantly changed the pattern of damage growth.

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“…The fracture mechanism of the joint is controlled by the stress concentration due to the contact angle and fiber compaction at the joint interface. It has been shown that all mechanical and adhesive composite joining methods impart some degree of stress concentration in the material [27,28]. Crack initiation and failure mechanisms at joint locations govern the macroscopic strength and failure of the composite [28,29].…”

Section: Bundle Joint Strengthmentioning

confidence: 99%

Laser Joining of Continuous Glass Fiber Composite Pre-Forms

Tan

Yao

2012

ASME 2012 International Manufacturing Science and Engineering Conference

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A laser fusion joining method is investigated for the purpose of through thickness strengthening of fiber pre-forms used in the vacuum infusion fabrication of thick composite structures. Laser joining is achieved without filler materials to replace adhesives, pins or stitches used in conventional composite fabrication.A two step joining process is developed to fuse fibers within a single bundle and between multiple fiber bundles. Finite element analysis is used to investigate the joint strength with respect to joint morphology. Joint strength is found to be a function of the fiber contact angle and packing density at the joint interface. Tensile tests show that laser joined fiber bundles exhibit higher strength than comparable fastening methods. Lessons learned from the axial joining of fiber bundles are applied to joining in the radial and thickness directions of 3d pre-form architectures. Flow induced joint morphology and densification effects observed in the axial direction indicate the need for a two step joining process in the thickness direction. Fiber compaction effects on joint strength in the axial direction motivate the need for high fiber packing fraction at joint interfaces in the thickness direction. INTRODUCTIONComposite pre-preg fabrication involves placing densely packed resin infused tapes of reinforcement fibers in layers (laminates) and then curing to produce thin shell structures. Composite components manufactured from pre-preg processes exhibit high fiber packing fraction and high strength along the fiber directions, but offer little strength perpendicular to the fiber directions. Laminates of pre-preg construction contain no fiber reinforcements aligned in the thickness direction due to the layer by layer assembly process. Thus, pre-preg fabrication is undesirable for making composite parts requiring high through thickness strength and fracture toughness. One method for improving the through thickness strength of pre-preg constructed components is to insert metal pins through layers of pre-preg prior to curing [1,2]. Mechanical pinning increases through thickness strength, relying on matrix load transfer mechanisms between the fibers and pins. The insertion of metal pins into a stack of pre-preg lamina displaces the fibers in the lamina and introduces

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Delamination and stitch failure in stitched composite joints

Cited by 11 publications

References 22 publications

Virtual crack closure technique: History, approach, and applications

Virtual crack closure technique: History, approach, and applications

Debonding of Stitched Composite Joints under Static and Fatigue Loading

Laser Joining of Continuous Glass Fiber Composite Pre-Forms

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