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February 25, 2004 Wind Turbine Blade Workshop @ Sandia HEXCEL COMPANY INFORMATION 1 Compression Testing for UD Carbon – Work in Progress… Bruno Boursier Hexcel R&T, Dublin, CA

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Page 1: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

1

Compression Testing for UD Carbon – Work in Progress…

Bruno BoursierHexcel R&T, Dublin, CA

Page 2: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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HEXCEL IS COMMITTED TO WIND ENERGY

Page 3: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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HEXCEL commitment through capital investment, but also product development AND Customers/Wind Energy Industry Support…

Page 4: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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As blades become larger substituting glass for carbonin some locations can make sense

Page 5: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Spar Caps are the most structural part of the blade airfoil

USING UD CARBON IN SPAR CAP PROVIDES HIGHEST PERFORMANCE/COST BENEFIT

Page 6: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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UD Glass versus UD Carbon

• Modulus of carbon UD (standard modulus) is nearly 4 times as high as E glass UD

• Compression strength of carbon UD is nearly 2 times as high as E glass UD

MODULUS, Tension MODULUS, Comp STRENGTH Tension STRENGTH Comp

UD, Glass 43 Gpa 42 Gpa 1100 Mpa 900 Mpa

UD Carbon 170 Gpa 159 Gpa 2400 Mpa 1600 Mpa

RATIO 4 3.6 2.4 1.7

Page 7: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Issues with compression testing of UD carbon

• Fiber alignment with load is critical• Very sensitive to defects > scatter• Very sensitive to buckling • Anti-buckling fixtures can introduce errors• Bottom Line: Can you use test results for

design?

Page 8: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Compression Testing Methods used at Hexcel

• SACMA SRM 1R-94: Most commonly used (US and EU) 1-2 mm thick specimens

• EN 2850B: EU only, same as above 2mm thick specimens. Tab failure common

• EN2850A: EU only, Celanese variation – difficult to get to work –Used mainly with multi-angular outer plies + machining

• IITRI: Not done at Hexcel anymore (not a standard)… but has merits• D3410 “beam test” HC sandwich laminate and steel skins – not an

option of 3410 anymore. Failure hard to detect, particularly in fatigue• ASTM D 6641: Wyoming Test Fixture –US only –Fairly new but

some customers requiring this specific test.

Page 9: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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1st Trials: SACMA SRM 1R-94 Fixture

> End loading only

> Parallel load path (bolt torque critical)

Page 10: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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SACMA SRM 1R-94 Specimens 0.500" Gage length @ 0.18"

3.18"

Spec. thickness TAB: 0.100"

Page 11: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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S-N curve in % of Static Strength vs. Nf (using SACMA Compression Fixture)With Optical Microscopy Observations

50

55

60

65

70

75

80

85

90

95

100

1 10 100 1,000 10,000 100,000 1,000,000 10,000,000

Close specimen surface delamination w ith some tab/specimen interface delamination

Close specimen surface delamination w ith some tab/specimeninterface delaminationDelamination at gage w ith macrobukling

Delamination at center of gage sectionw ith macrobuckling

Delamination at center of gage and possible plastic microbuckling (kink band)

Delamination a small distanceaw ay from surface of specimenin tab area. Small delaminations ingage area. (needs SEM evaluation) Small delaminations in gage area.

Tab/specimen interface delaminations.45 degree shear failure

Need to lower CV in Static first!

Page 12: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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2nd Trials: Wyoming Test Fixture

Page 13: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Wyoming Test Fixture

Load Introduction: End + Shear loading

No parallel Load path in gage area

Page 14: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Wyoming Test FixtureTabbed Specimens

0.1875" 4x Tab Thickness

ref. A 5.50"

0.50"

Gage

Page 15: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Wyoming Test FixtureMachined Specimens

5.50"ref. (a)

0.15"

~0.5" R

0.50"

Page 16: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Tapered specimen very resilient to buckling.Buckling stress > 12X compression strength

Page 17: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Comparison of Test Methods to Determine Static Compressive Strenth of a Vacuum-Bag Processed

Unidirectional Epoxy/Carbon Laminate

0

50

100

150

200

250

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

ksi

Red - SACMA/TabbedBlue - WTF/TabbedGreen - WTF/Tapered

Wyoming Test Method using thicknesstapered specimen result in conservativecompression value w ith significantly lessvariance

CV: 12% CV: 10% CV: 4%

Page 18: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Wyoming Test FixtureFatigue Results

• Work in Progress (R=0.1, f=5Hz, load control)• So far, very high life at 90% of static strength:

majority over 3 millions cycles• No macro-buckling seen• No end crushing • Because less scatter in static, more confident of

% static load for each specimen

Page 19: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Wyoming Test FixtureTypical Fatigue Failure Mode

Page 20: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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“Pure” Compression Fatigue: Fibers showing compression rings after 3 million cycles

Page 21: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Typical Outer Ply Delamination Seen in Fatigue of Tapered Specimen

Outer ply delamination, but, gage section still end loaded

Page 22: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Process/Fiber Ranking using WTF/tapered specimens

Compressive Strength Wyoming Test Fixture - Tapered Specimens

0

20

40

60

80

100

120

140

160

180

ksi

Ave. = 152.2N=11COV = 2.8%

Ave. = 145.4N=5COV = 9.9%

Ave. = 139.9N=11COV = 8.5%

Ave. = 121.5N=11COV = 22.1%

Error bars are +/- 95% Confidence Intervals for Population Mean

Ave. = 109.6N=11COV = 12.8% Ave. = 97.02

N=10COV = 11.5%

P1/F1 P1/F2 P2/F1 P2/F2 P3/F1 P3/F2

Page 23: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Results Highlights and Discussion

• Thickness tapered specimens greatly reduced “parasitic” failure modes such as tab failure, buckling. Static scatter is reduced.

• Thickness tapered specimens allow for testing thick laminates.

• More validation tests needed. This test was however successfully used to rank processes and fibers (validated by outside lab).

• Development of strain measurement techniques are planned

Page 24: Compression Testing for UD Carbon – Work in Progress…windpower.sandia.gov/2004BladeWorkshop/PDFs/BrunoBoursier.pdf · Compression Testing for UD Carbon – Work in Progress

February 25, 2004 Wind Turbine Blade Workshop @ SandiaHEXCEL COMPANY INFORMATION

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Future Development• Need cooperative work with Universities,

National Laboratories, industry members to facilitate introduction of carbon fibers in WE blades:– Validate compression testing technique of UD carbon

for static and fatigue > standard ?– Develop test for defects “tolerance” to go from coupons

to real blades– Develop NDE techniques