Compression Strength of Carbon Fiber Laminates Containing Flaws with Fiber Waviness

Avery, Darrell; Samborsky, Daniel D.; Mandell, John F.; Cairns, Doug S.

doi:10.2514/6.2004-174

Cited by 20 publications

(18 citation statements)

References 4 publications

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“…The ply drop problem is of particular concern for wind turbine blades using carbon fibers for three reasons: first, the more directional elastic constants of carbon fiber laminates often increase the tendency to delaminate relative to glass; second, to reduce cost, the plies are often thicker in composites for wind turbine blades relative to aerospace applications; and third, the ultimate and fatigue strains in compression for lower cost forms of carbon fiber laminates are lower than for glass, [28,29], and may be design drivers in some cases.…”

Section: Delamination At Ply Dropsmentioning

confidence: 99%

Analysis of SNL/MSU/DOE fatigue database trends for wind turbine blade materials.

Mandell

Ashwill²,

Wilson

et al. 2010

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This report presents an analysis of trends in fatigue results from the Montana State University program on the fatigue of composite materials for wind turbine blades for the period 2005-2009. Test data can be found in the SNL/MSU/DOE Fatigue of Composite Materials Database which is updated annually. This is the fifth report in this series, which summarizes progress of the overall program since its inception in 1989. The primary thrust of this program has been research and testing of a broad range of structural laminate materials of interest to blade structures. The report is focused on current types of infused and prepreg blade materials, either processed in-house or by industry partners. Trends in static and fatigue performance are analyzed for a range of materials, geometries and loading conditions. Materials include: sixteen resins of three general types, five epoxy based paste adhesives, fifteen reinforcing fabrics including three fiber types, three prepregs, many laminate lay-ups and process variations. Significant differences in static and fatigue performance and delamination resistance are quantified for particular materials and process conditions. When blades do fail, the likely cause is fatigue in the structural detail areas or at major flaws. The program is focused strongly on these issues in addition to standard laminates. Structural detail tests allow evaluation of various blade materials options in the context of more realistic representations of blade structure than do the standard test methods. Types of structural details addressed in this report include ply drops used in thickness tapering, and adhesive joints, each tested over a range of fatigue loading conditions. Ply drop studies were in two areas: (1) a combined experimental and finite element study of basic ply drop delamination parameters for glass and carbon prepreg laminates, and (2) the development of a complex structured resininfused coupon including ply drops, for comparison studies of various resins, fabrics and pry drop thicknesses. Adhesive joint tests using typical blade adhesives included both generic testing of materials parameters using a notched-lap-shear test geometry developed in this study, and also a series of simulated blade web joint geometries fabricated by an industry partner.

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Section: Delamination At Ply Dropsmentioning

confidence: 99%

Analysis of SNL/MSU/DOE fatigue database trends for wind turbine blade materials.

Mandell

Ashwill²,

Wilson

et al. 2010

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“…This results in a loss of strength. Fiber waviness also decreases compressive strength due to the fibers are starting in a semi-buckled orientation making a buckling failure more likely (Avery, 2004). The wave category of defect is broken into out-of-plane (OP) waves, in which the wavy fibers are elevated out of the plane of the laminate, and in-plane (IP) waves, where the fibers remain in the plane.…”

Section: Common Blade Flaw Typesmentioning

confidence: 99%

Investigation of the Effect of In-Plane Fiber Waviness in Composite Materials through Multiple Scales of Testing and Finite Element Modeling

Lerman¹

2015

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“…4,6 Recent attention has been given to this problem in the aerospace community in the area of tapered flex beams for helicopter rotors. 8,9 The ply drop problem is of particular concern for wind turbine blades using carbon fibers for three reasons: first, the more directional elastic constants of carbon fiber laminates often increase the tendency to delaminate relative to glass; second, to reduce cost, the plies are often thicker in composites for wind turbine blades relative to aerospace applications; and third, the ultimate and fatigue strains in compression for lower cost forms of carbon fiber laminates are lower than for glass, 10,11 and may be design drivers in some cases. Thus, while ply drops may not have been a major problem for glass fiber blades, they may prove critical with carbon fibers.…”

Section: Introductionmentioning

confidence: 99%

Delamination and Failure at Ply Drops in Carbon Filter Laminates Under Static and Fatigue Loading

Samborsky

Avery

Agastra

et al. 2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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Delamination at ply drops in composites with thickness tapering has been a major concern in aerospace applications of carbon fibers, where the plies are typically very thin. This study explored the resistance to delamination in fatigue of hybrid carbon fiber and glass fiber prepreg laminates containing various ply drop geometries, and using thicker plies typical of wind turbine blades. Strain levels to produce significant delamination at both carbon and glass fiber ply drops were determined and compared in terms of a simple delamination model. The carbon fiber laminates with ply drops, while performing reasonably well under static loads, delaminated in fatigue at low maximum strain levels except for the thinnest ply drops. The lower elastic modulus and higher interlaminar toughness of the glass fiber prepreg resulted in much higher strains to produce delamination at equivalent ply drops, compared with carbon fiber prepreg using the same resin system. The results indicate that the thickness of ply drops with carbon fibers should be much less than those commonly used for glass fibers.

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Compression Strength of Carbon Fiber Laminates Containing Flaws with Fiber Waviness

Cited by 20 publications

References 4 publications

Analysis of SNL/MSU/DOE fatigue database trends for wind turbine blade materials.

Analysis of SNL/MSU/DOE fatigue database trends for wind turbine blade materials.

Investigation of the Effect of In-Plane Fiber Waviness in Composite Materials through Multiple Scales of Testing and Finite Element Modeling

Delamination and Failure at Ply Drops in Carbon Filter Laminates Under Static and Fatigue Loading

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