advancements in composite materials for wind blades

August 31, 2016

“Advancements in Composite Materials for Wind Blades”

Dave Hartman and Tom DeMint

Sandia National Laboratory2016 Wind Turbine Blade Workshop

Copyright © 2016 Owens Corning. All Rights Reserved

Production of energy with no emission of CO2 (wind, tidal, solar, geothermal)

Providing the basic infrastructure to deliver clean water to excess of 5-billion people

Providing housing and infrastructure to a growing population in developing and third-world countries

Reducing the weight of modes of transportation to respond to increasing cost of energy

CLEAN ENERGY

WATER INFRASTRUCTURE

URBAN INFRASTRUCTURE

INDUSTRIAL LIGHT WEIGHTING

COMPOSITES OPPORTUNITY - GLOBAL MEGATRENDS

2© iStock pictures

DRIVERS FOR COMPOSITES IN THE WIND MARKET

3

Longer and lighter blades Increased blade performance Development of low-wind

and off-shore sites Cost-of-energy reduction Repowering and extension of

service life

DRIVERS FOR COMPOSITES IN THE WIND MARKET

Lighter Stiffer Blade Design

Productivity Manufacturing

Details

Durability Service Life

4

Stiffness per $

Composite materials

BLADE MATERIAL SELECTION BASED ON STIFFNESS PER $

Composite materials offer the best balance of stiffness and density

Source: Adolphs et.al, “Ultrablade® Fabrics - Reducing the Cost of Wind Energy” SNL 2012 Wind Turbine Blade Workshop

COMPOSITE MATERIAL DESIGN TO REDUCE COST PER MWh

Glass fiber reinforcement provides cost advantage for structural composites

0

500

1000

1500

2000

2500

3000

3500

4000

4500

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Te

nsile

Str

ess, M

Pa

Tensile Strain, %

Vintage E-Glass

Advantex®

S-Glass

WindStrand®

Increase inModulus

Increase inStrength

GLASS FIBER EVOLUTION FOR BLADE SPAR CAP

Source: Hartman et.al, “Advances in Blade Design and Material Technology” WindPower 2005 Technical Proceedings

Increasing performance for the Wind Industry with higher modulus glass fiber

HIGH PERFORMANCE UD FABRIC MANUFACTURING

Stitching Technology- Yarn Denier- Pattern- Tension, etc

Winding Process

Warp Constructions- Glass - Micronage- Tension, etc

Typical Stitching Patterns

Fabric Characteristics- Uni-, biaxial, triaxial- Architecture - Alignment- Skewability- Areal weight

- UD1200- UD1800

Each UD fabric manufacturing process step is critical to the overall performance

0

200

400

600

800

1000

1200

0 10 20 30 40 50 60

Lam

inat

e S

tre

ngt

h (

MP

a)

Laminate Stiffness (GPa)

56% Vf

53% Vf

Std. fabrics

Ultrablade® fabrics

Blade Length [m]

Thic

knes

s [m

]

Z

X

Wind

Blade Length [m]

Thic

knes

s [m

]

Z

X

Blade Length [m]

Thic

knes

s [m

]

Blade Length [m]

Thic

knes

s [m

]

Z

X

Z

X

WindWind

Source: Owens Corning Data, Optimat, Independent test reports

HIGH PERFORMANCE ULTRABLADE® FABRICS FOR SPAR CAP

Ultrablade® fabrics provide significant improvement in modulus, strength with increased fiber volume and alignment in UD laminates

Ultrablade® Fabrics

Triaxial Fabrics

Biaxial Fabrics

Adhesive

FATIGUE PERFORMANCE OF ULTRABLADE® FABRICS

Load simulation identified the fatigue hot-spot for a typical wind blade


FATIGUE CALCULATION ACCORDING MINER’S RULE

Dam

age

D

Mean Stress [MPa]

Stress Amplitude [MPa]

Goodman Diagram with Rain Flow count

Goodman Diagram up to 2x106 cycles Calculated Fatigue Damage

FATIGUE DAMAGE ANALYZED FOR IMPROVED DESIGN


Blade design optimized with weight reduction from improved laminate fatigue life

HIGH PERFORMANCE FIBERS AND FABRICS ENABLE LONGER BLADES

6,05,55,04,54,0

700

650

600

550

500

450

400

350

LOG (N)

Pe

ak S

tre

ss [

MP

a]

ADV

H

Fiber

Source: Owens Corning Risoe / DTU tests 2013 on UD laminates, Momentive Epoxy resin L135/H137800750700650600

1200

1100

1000

900

800

700

Compression Strength, MPa, 95/5% CI

Te

nsile

Str

en

gth

, M

Pa

, 9

5/

5%

CI

Advantex® E

Windstrand® H

Fiberglass type

Higher composite stiffness and fatigue performance for longer blade life reduces the cost of energy

Fatigue Performance at R=0.1, E-glass and H-glass Uni-directional Fabric/epoxy for spar cap

12

HIGH PERFORMANCE FIBERS AND UNI-DIRECTIONAL COMPOSITE PROPERTIES

PropertyTest

MethodUnit E-Glass

ECR-Glass

Boron freeH-Glass R-Glass S-Glass Carbon

Fiber and Bulk Glass PropertiesDensity ASTM C693 g/cm3 2.63-2.64 2,66 2,65 2.55 2,48 1.79

Refractive Index (bulk annealed) ASTM C1648 - 1.562-1.565 1.567 1.558 1.54 1,522

Conductivity ASTM C177 watts/m•K 1.0-1.3 1.22 1.34 6.83

Pristine Fiber Tensile Strength ASTM D2101 MPa 3815-3830 4050 4635 4450-4580 4830-5080 4400

Specific Pristine Strength Calculation × 105 m 1.48-1.49 1.56 1.81 1.74 2.01-2.12 2.46

Young's Modulus GPa 78-79 82 87.5 87 88 230

Specific Modulus Calculation × 106 m 3.05 3.15 3.41 3.48 3.67 12.8

Elongation at Break % 4.8 4.9 4.9 5.35 5.5 1.8

Thermal Properties

Coefficient of Thermal Expansion, 23-300 °C ASTM D696 × 10-6 cm/cm•°C 5.9-6.6 6.6 6.3 4.1 3.4 - 0.6

Specific Heat @ 23 °C ASTM C832 kJ/kg•K 0.807 0.79 0.75 0.810 1.130

Fiber Tensile Strength v. Temperature

Pristine Fiber Tensile Strength, -196 °C ASTM D2101 MPa 5310 5935 7220 7826

Pristine Fiber Tensile Strength, 22 °C ASTM D2101 MPa 3815 4050 4635 4450 5047 4400

Fiber Weight Loss @ 96 °C, 24 hours, 17µm

10% HCl % 31.68 7.88 7.59 1.53 0.05

10% H2SO4 % 32.00 6.91 6.48 1.17

1 N Nitric % 23.47 7.21 6.67 1.42

NaOH pH=12.88 % 5.40 3.24 12.6 19.34 1.10

Impregnated Strand PropertiesTensile Strength ASTM D2343 MPa 2000-2500 2200-2600 2400 -2800 3050-3400 3410-3830 4000

Tensile Modulus ASTM D2343 GPa 78-80 81-83 90 - 91 89-91 86.9-95.8 230

Toughness ASTM D2343 MPa 37 56 69 82-90

Unidirectional Composite Properties1

Tensile Strength ISO 527-5 MPa 1120 1200 1260 1560 1550 1780

Tensile Modulus ISO 527-5 GPa 46 48 52.5 51.6 53 153

Poisson's Ratio ASTM D638 - 0.29 0.33 0.33 0.32 0.27 0.28

Fiber Volume Fraction ASTM D2734 % 60 60 60 60 60 57 2

1 MGS RIM 135 epoxy + RIMH 137 hardener 2 EPON 826 DM HS-Carbon Fiber OC data pub.2011

Glass and Carbon Fiber linear-elastic behavior enables structural composites when load sharing occurs at the fiber-matrix interphase 13

BLADE DESIGN AND MATERIAL INFLUENCE WEIGHT

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

0.000 0.050 0.100 0.150 0.200 0.250 0.300

Cal

cula

ted

Bla

de

We

igh

t (t

on

ne

)

Deflection (mm)

Closed Form Solution Fiber Volume Sensitivity Analysis on Stiffness

Advantex (FVF 53) /Epoxy-5250

Advantex (FVF 57)/Epoxy-5250

Advantex (FVF 60)/Epoxy-5250

H-Glass (FVF 53)/Epoxy-5250



S-Glass (FVF 53)/Epoxy-5250



T-300 (FVF 53)/Epoxy-5250

T-300 (FVF 57)/Epoxy-5250

T-300 (FVF 60)/Epoxy-5250

Hybrid-Advantex (FVF 60) cover + T-300 (FVF 60) web

Carbon Design

Glass Design

Hybrid Design-Glass skin, Carbon spar

Thicker Air Foil Design

Glass and carbon fiber linear-elastic behavior enables lighter blades with load sharing depending on the aero-elastic design

Source: Owens Corning data first order approximation closed form solution of uniform bending load.

15Source: Joseph Cariveau approved reference to LM Website: LM Wind Power layup of LM 88.4 P spar cap, reprinted with permission.

BUILDING THE LONGEST WIND TURBINE BLADE

High fiber modulus and strength for blade root

Fabric form influences blade root joint design

Simulation of fiber, fabric, and laminate property on blade root joint durability

HIGH PERFORMANCE FIBERS AND FABRICS ENABLE WIND BLADE ROOT JOINT DURABILITY

Design simulation predicted higher modulus fiber/fabric reduced the bearing load transferred to the bolt. The lower axial stress in the bolt

substantially increased the blade joint bolt fatigue life durability.

HIGH PERFORMANCE FIBERS AND FABRICS ENABLE WIND BLADE ROOT JOINT DURABILITY

®®

Simulation of axial stress in the joint tension bolt and laminate load in bearing assumes good matrix cohesion and adhesion at the fiber-matrix interface

Laminate load sharing in bearing

HIGH PERFORMANCE FIBER-MATRIX INTERPHASE IMPROVES BLADE ROOT JOINT DURABILITY

19

Acoustic and fracture surface analysis of 45o tension in Advantex® glass/epoxy lamina show the improved fiber-matrix adhesion leads to a higher transverse strength

Source: Owens Corning WindStrand® fibers and data. Panels dry-wound roving and infused using Momentive epoxy RIMR 135/H137

E-glass UD/epoxy WindStrand® UD/epoxy

Higher composite fiber-matrix adhesion for durability

HIGH PERFORMANCE FIBER-MATRIX INTERPHASE IMPROVES BLADE DURABILITY

THE DESIGN, RELIABILITY AND DURABILITY OF POLYMER COMPOSITE MATERIALS IS ENABLED BY INTERFACE SCIENCE

Interface science from physical chemical bonding mechanisms to micro-macro structure-property relationship is required for theoretical and analytical

approaches to mimic composite material performance

• Molecular Dynamics predict water molecules break Si-O-Si bonds creating a high concentration of Si-OH silanol groups on the glass surface

• Surface flaw crack initiation ~1µm fractures at a lower stress in tension than the glass fiber intrinsic strength, accelerated by high temperature

• Experimental validation: liquid nitrogen immobilizes water and testing shows up to 35% higher fiber median strength, and

• Vacuo treatment with time reverses water effect on glass which enables 25% higher fiber median strength

• Silane adsorption bonding glass and adhesion to matrix, protects glass

3500

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4100

4300

4500

4700

4900

1 10 100 1000 10000 100000

Av

era

ge

Str

ess

(M

Pa

)

Log Time (Minutes)

Impact on Fiber Strength of Holding Sample In Vacuo and Testing in Ambient

0

1000

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6000

7000

-200 -100 0 100 200 300 400 500 600 700 800

Str

ess

(M

Pa

)

Heat Treatment Temperature C

Strength of Fibers Treated at Temperature and Tested at Room Temperature

GLASS COMPOSITION AND SURFACE PROTECTION REDUCE STRESS CORROSION FROM MOISTURE AND TEMPERATURE

Source: Owens Corning data single fiber testing, glass stress corrosion simulation

MACRO COUPON TESTING COMMON FOR DESIGN AND MANUFACTURING DETAILS, MICRO FOR INTERFACE SIMULATION

Validation of micro-macro property correlation is important for predicting composite material performance

0

500

1,000

1,500

2,000

2,500

3,000

0 10 20 30 40 50 60

Te

nsile

Str

en

gth

(M

Pa)

Glass Fiber Manufacturer

MACRO FIBER STRENGTH IMPROVES BY 3X FOR GLASS COMPOSITION, 2X FOR ALL PROCESS/PRODUCT PARAMETERS,~1.3X FOR FIBER DIAMETER/TEX

1,000

1,200

1,400

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3,000

10 15 20 25 30 35

Te

nsile

Str

en

gth

(M

Pa)

Fiber Diameter (microns)

1,000

1,200

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1,600

1,800

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2,200

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0 1000 2000 3000 4000 5000 6000 7000 8000

Te

nsile

Str

en

gth

(M

Pa)

Strand Tex (g/Km)

0

500

1000

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3500

4000

4500

0 1 2 3 4 5 6

Te

nsil

e S

tre

ng

th (

MP

a)

Tensile Strain (%)

Vintage E-Glass

State-of-Art E-Glass

S-Glass


MACRO FIBER-MATRIX ILSS INFLUENCED UP TO 1.4X BY MATRIX, 1.3X BY FIBER DIAMETER, 1.5X DRY AND 1.5-3X HOT/WET AGED INTERPHASE

Shear Strength in Epoxy - All Products

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0 5 10 15 20 25 30 35


Sh

ea

r S

tre

ng

th (

MP

a)

Wet Shear Strength in Epoxy - All Products

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0 5 10 15 20 25 30 35


Sh

ear

Str

en

gth

(M

Pa)

Shear Strength in Polyester - All Products

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0 5 10 15 20 25 30 35


Sh

ea

r S

tre

ng

th (

MP

a)

Wet Shear Strength in Polyester - All Products

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0 5 10 15 20 25 30 35


Sh

ear

Str

en

gth

(M

Pa)


GOOD COMPOSITE FRACTURE TOUGHNESS WITH HIGH FIBER STRENGTH, MATRIX MODULUS, AND INTERFACIAL ADHESION

Uni-directional glass fiber-reinforced polymer interlaminarfracture crack growth correlates to fatigue performance


Zangenberg1 et al suggested that glass UD fabric/polyester fatigue failure mechanisms are analogous to cracking in thin films proposed by Beuth2

1 J. Zangenberg et al, “Fatigue damage propagation in unidirectional glass fiber reinforced composites made of a non-crimp fabric”, Journal of Composite Materials, 20132 J. L. Beuth, Jr, “Cracking of thin bonded films in residual tension,” 1992; International Journal of Solids and Structures; Figures used with license.

),,(2 1

2

h

aG

E

h

Gss

Gss= Steady state strain energy release rateG = non-dimensional crack area

ahCrack extension

Interply resin layer, E1

90o weft fibers

Axial fibers, E2, 0o

Crack channeling

Two types of fatigue crack propagation: • extension• channeling

FATIGUE CRACK GROWTH CHARACTERIZATION

Depending on interply resin layer thickness, the crack is arrested due to a decrease in its energy release rate in a compliant material approaching a stiffer material.

0

500

1000

1500

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3000

100 150 200 250 300 350 400

Axial Stress, , MPa

Stra

in E

ne

rgy

Re

leas

e R

ate

, G

ssJ/

m2

G1C

If Gss< G1C then there is no crack growth

Steady state strain energy release rate at 50m interply resin layer vs. axial stress

),,(2 1

2

h

aG

E

h

Gss

Gss= Steady state strain energy release rateG = non-dimensional crack area

ahCrack extension

Interply resin layer, E1

90o weft fibers

Axial fibers, E2, 0o

REDUCE FATIGUE CRACK GROWTH WITH INCREASED INTERPLY TOUGHNESS

One way to reduce fatigue crack growth is to increase interplyG1C matrix critical strain energy release rate or “toughness”

Strain Energy Release Rate,G (J/m2) required for crack growth at = 200 MPa vs interply resin thickness h, mm

0

200

400

600

800

1000

1200

1400

1600

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20 30 40 50 60 70 80 90 100 110 120

Stra

in E

ne

rgy

Re

leas

e R

ate

, J/m

2

Interply Resin Layer Thickness, h, mm

Increasing the interply resin layer thickness by decreasing FVF, increases the strain energy release rate needed for cracks to propagate between plies

REDUCE FATIGUE CRACK GROWTH WITH INCREASED INTERPLY RESIN LAYER THICKNESS

Reduce fatigue crack growth by increasing the interply resin layer thickness with optimizing the fabric architecture or decreasing the fiber volume fraction

NIST AND NW COLLABORATION ON INTERPHASE CHARACTERIZATION

Determining the relationship between fiber-matrix interphase and composite part performance enables more effective

development for increasingly robust service life requirements

Hypothesis: a test methodology to characterize fiber-matrix interfacial performance that will provide insight for:

reduced crack initiation and propagation rate in fatigue

higher stress corrosion resistance

Interface/interphase input for simulation

consistent robust polymer composites

Test Methodology: determine fiber surface interphase relationships to mimic improved composite performance

interfacial shear strength

fiber fragmentation and critical length measurements

atomic force microscopy, multi-functional molecular probes

advanced fluorescence microscopy

Thank You !

[email protected]

[email protected]

Georg Adolphs, Marcus Liu and Richard Veit contributing

QUESTIONS ?