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Research Papers

Comparison of Tensile Fatigue Resistance and Constant Life Diagrams for Several Potential Wind Turbine Blade Laminates

[+] Author and Article Information
Daniel D. Samborsky, Timothy J. Wilson, John F. Mandell

Department of Chemical and Biological Engineering, Montana State University, Bozeman, MT, 59717

J. Sol. Energy Eng 131(1), 011006 (Jan 06, 2009) (10 pages) doi:10.1115/1.3027510 History: Received March 22, 2008; Revised September 09, 2008; Published January 06, 2009

New fatigue test results are presented for four multidirectional laminates of current and potential interest for wind turbine blades, representing three types of fibers: E-glass, WindStrand™ glass, and carbon, all with epoxy resins. A broad range of loading conditions is included for two of the laminates, with the results represented as mean and 9595 confidence level constant life diagrams. The constant life diagrams are then used to predict the performance under spectrum fatigue loading relative to an earlier material. Comparisons of the materials show significant improvements under tensile fatigue loading for carbon, WindStrand, and one of the E-glass fabrics relative to many E-glass laminates in the 0.5–0.6 fiber volume fraction range. The carbon fiber dominated laminate shows superior fatigue and static strengths, as well as stiffness, for all loading conditions.

Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Constant life diagram for [90∕0∕±45∕0deg]s E-glass/polyester laminate (0.36 fiber volume fraction) based on S-N data for 13 R-values, three-parameter mean S-N model, axial (0deg) load direction (5) (normalized by the static tensile strength)

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Figure 2

DB and rectangular (top) test geometries (tab thickness=1.6mm)

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Figure 3

Failed fatigue specimens, showing grip-edge failure for a rectangular specimen (top) and gage section failure for a dog-bone specimen

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Figure 4

Load waveforms showing definition of terms (top) and illustration of R-values (bottom, R=minimum stress/maximum stress)

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Figure 5

Material DD16 R=−1S-N dataset with three curve fits, glass/polyester laminate (shown with static compressive strength)

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Figure 6

Typical stress versus cycles to failure dataset showing mean and 95∕95 fits, and 95∕95 fit from a log cycles model (5), using a three-parameter S-N model, R=0.1, material DD16, axial direction (model fit to all fatigue data)

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Figure 7

Comparison of materials QQ1 (E-glass) with material P2B (carbon/E-glass hybrid) at three R-values, showing mean and 95∕95 fits. (a) R=10, (b) R=−1, and (c) R=0.1.

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Figure 8

Tensile fatigue comparison of e-glass/epoxy materials QQ1 and SN5-0291, and Windstrand/epoxy material WS1, R=0.1, stress S-N

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Figure 9

Tensile fatigue comparison of E-glass/epoxy materials QQ1 and SN5-0291, and WindStrand/epoxy material WS1, R=0.1, strain S-N

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Figure 10

Tensile fatigue comparison of E-glass/epoxy materials QQ1 and SN5-0291, and WindStrand/epoxy material WS1, R=0.1, calculated 0deg ply stress (EL⋅strain) versus cycles

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Figure 11

Mean axial constant life diagram for material DD16 (normalized to the mean static tensile strength)

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Figure 12

Mean axial constant life diagram for material QQ1 (normalized to the mean static tensile strength)

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Figure 13

95∕95 axial constant life diagram for material QQ1 (normalized to the mean static tensile strength)

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Figure 14

Comparison of materials QQ1 (E-glass) and P2B (carbon dominated), axial direction, stress constant life diagram, mean stress S-N model

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Figure 15

Comparison of materials QQ1 (E-glass) and P2B (Carbon Dominated), strain constant life diagram, mean strain S-N model

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Figure 16

Mean transverse constant life diagram for material QQ1T

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Figure 17

Mean transverse constant life diagram for material P2BT

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Figure 18

Stress scale factors applied to the WISPERX spectrum to achieve a Miner’s sum equal to 1 (using the mean stress CLD)

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Figure 19

Strain scale factors applied to the WISPERX spectrum to achieve Miner’s sum equal to 1 (using the mean stress CLD)

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