Advances in Fiberglass Properties for Wind Turbine Blades
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Presentation by Tom DeMint of Owens Corning at CAMX on October 15, 2014. As the wind power energy generation industry continues to develop, one of the main objectives of turbine rotor blade manufacturers is to reduce total energy production cost to align wind power with other energy sources. Energy produced by wind turbines is more widely available than ever before; nevertheless the industry is constantly looking for ways to further optimize the cost of energy (CoE) as one of its foremost goals. The turbine, together with its rotor blades, plays an essential role and is one of the major components of these machines in terms of cost. It generates the torque which drives the generator and is responsible for the range of conditions energy can be extracted from the available wind. Wind farms are now constructed and operate in challenging off-shore as well as on-shore locations with differing wind speed conditions. Glass fiber composite rotor blades have contributed greatly to the success of this sustainable energy source and have allowed the wind industry to make significant advances in recent times, especially in off-shore and in low-wind locations. One of the most important advances has been the progressive technology applied to the properties of glass fiber leading to the development of high modulus glass types for lighter composites offering greatly enhanced resistance to fatigue at an affordable cost. The technological advances in glass fiber properties has resulted in rotor blades of ever greater length - beyond 85m – dimensions deemed unreachable less than a decade ago. This presentationl highlights advances in the material properties of glass fiber to help designers and engineers conceive blades which are lighter yet with increased length, improved aerodynamic performance with resistance to higher, long-term fatigue loads which ultimately enables wind turbines to increase power yield and therefore reduce the cost of energy.
Transcript of Advances in Fiberglass Properties for Wind Turbine Blades
Copyright © 2014 Owens Corning. All Rights Reserved
Advances in Fiberglass Properties
for Wind Turbine BladesTom DeMint - Technical Marketing, Owens Corning
Marcus Liu - Technical Marketing, Owens Corning
Dave Hartman - Science & Technology, Owens Corning
Georg Adolphs - Technical Marketing, Owens Corning
Richard Veit - Science & Technology, Owens Corning
October 13-16, 2014
Orange County Convention Center
Orlando, FL
Evolution of Glass Fiber Innovation
1939: E-glass - Boron added to glass for electrical properties
1965: R-glass - Higher performance
1968: S and S-2 Glass® - High strength and modulus (high melting power needed)
1974: AR-glass - Alkali resistant
1978: E-CR Glass - Corrosion resistant
1996: Advantex® ECR Glass and melting technology
- Boron free E-glass, ECR-glass (superior corrosion resistance to traditional E-glass)
- Breakthrough in melting technology for large capacity furnaces
2006: R and H-glass melting technology
- Combines High modulus glass and Advantex® - scale melting technology
2009: S-glass direct melt large capacity technology
- Production in large capacity furnaces with higher fiber homogeneity
2014: Windstrand® product line - Superior sizing chemistry
Large capacity furnaces provide industrial supply of high performance glass fibers
Turbine Performance Trends in theWind Energy Market
Market Evolution
ON-SHORE (HIGH WIND)
Continued pressure to reduce capital/operating costs
Requires cost effective solutions
Reduce manufacturing and operating costs
BETTER RELIABILITY
25 year blade life
107 fatigueload cycles
OFF-SHORE
Large turbines (8MW)
Larger blades(75m - 80m, glass, carbon)
Extreme environments
ON-SHORE (LOW WIND)
Longer blades to harvest
energy in low wind speed
regions and cold climates
The scaling problem
Blade Length
Bla
de
Weig
ht
Aerodynamic loads scale up linearly with blade length, which of itself might not require an increase inmaterial properties.
However blade mass, gravitational loads, and fatigueloads scale up exponentially with blade length.
Material requirements are increasing with increasing blade length and mass.
Market needs higher Modulus/$, Strength/$
Material Data and Advances in Properties
WindStrand®
2000Advantex® E/ECR-
glass with advanced sizing for epoxy
Windstrand®
3000High modulus H-glass
with advancedsizing for epoxy
Ultrablade®
G3WS3000
UD Fabric(eopxy)
New Products for Wind Turbine Blades
Unidirectional Fiberglass Fabric/Epoxy Laminate Modulus Trend
Source: Independent test lab results 2009-2014 (IMA Dresden, WMC, TPI Composites);
Momentive Epoxy resin RIMR 135/H137
Linear trend of increasing UD glass fabric modulus with increasing FVF approaching 50 Gpa using high modulus glass
Longitudinal Modulus Ex, Measured vs. Theoretical
Longitudinal Modulus Ex, Measured vs. Theoretical
We observe good agreement between measured and theoretical longitudinal laminate modulus Ex
43210-1-2-3-4
99
95
90
80
70
60
50
40
30
20
10
5
1
Difference Measured-Theoretical Modulus E1 [GPa]
Pe
rce
nt
-0.2642 0.8623 9 0.427 0,241
0.04723 1.016 9 0.347 0,393
Mean StDev N AD P
ADV 78GPa
H 85GPa
Fiber
Normal - 95% CI
210-1-2
5
4
3
2
1
0
Difference measured-theoretical
Fre
qu
en
cy
Mean -0.08867
StDev 1.004
N 22
Ex Measured- Ex Theoretical
Glass Bulk Modulus used for theoretical calculations
Ebulk Advantex : 78 GPa
Ebulk H-glass: 85 GPa
UD/Epoxy Static Strength Properties, Characteristic Values (95%/5% Confidence Interval)
Source: IMA Dresden test results 2009-2014 on UD Fabrics, Momentive Epoxy resin RIMR 135/H137
We see a correlation
between UD/epoxy tensile
and compressive strength
Laminate Behavior Transverse to the Longitudinal Fibersin Tension
Natural transverse contraction can be constrained by adjacent plies (often 90o plies) compared to a pure UD lamina.
IFF cracksThis constraint may lead to limited transverse cracking, which may be acceptable in some rotor blades. However the average Inter Fiber Fracture strength (IFF) is measured and used for blade designs.
Tensile LoadBearing Capability
Source: IMA Dresden test results 2009-2014 on UD Fabrics,
Momentive Epoxy resin RIMR 135/H137
Introduce WindStrand® “IFF Safety Factor” = 1.5
E-glass UD H-glass EPW17 WS3000
Low
er is
bette
r
“Max Poisson” Transverse Strain
Transverse Strain Capability
Acoustic and Fracture Surface Analysis of 45o Tension in Advantex®/epoxy lamina Panels
Source: OC WindStrand® fibers and data. Panels dry-wound
roving and infused using Momentive epoxy RIMR 135/H137
E-glass UD/epoxy WindStrand® UD/epoxy
Better fiber matrix
adhesion leads
to higher transverse
strength
Static Longitudinal Tensile Failure Modes, UD E-glass vs. WindStrand® Fabric/Epoxy
Source: OC test data UD1800 Fabrics,
Momentive epoxy resin RIMR 035/038
x
Ultrablade® G3 vs G2 Fatigue
Performance (Stress Amplitude)
Higher Initial Static
Tensile Strength
Leads to Longer Life
Number of Cycles to Failure
Strength Knockdown from Fiber to LaminateDamage Accumulation
Better fatigue performance leads to longer life and lower design knockdowns from damage accumulation
Source: OC data on WS2000 UD Fabrics,
Momentive epoxy RIMR 135/H137
0
500
1000
1500
2000
2500
3000
3500
4000
4500
0 1 2 3 4 5 6
Ten
sile S
tren
gth
(M
Pa)
Tensile Strain (%)
Vintage E-Glass
State-of-Art E-Glass
S-Glass
Vintage E-glass
Advantex®
S-glass 0
200
400
600
800
1000
1200
1400
WS2000CouponMean
UD1200CouponMean
UD1200CouponR(95%)
UD1200Spar Cap
Mean
FatigueR=0.110^6
cycles
00 Tensile Strength 55%Vf (MPa) Knockdown
Advantex®
Fatigue Performance, E-glass vs. H-glass UD Fabric/epoxy
Higher Initial Static Strength Leads to Longer Life
Source: Risoe / DTU tests 2013 on UD laminates,
Momentive Epoxy resin L135/H137
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
800750700650600
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 typeFiberglass type
Advantex® E
Windstrand® H
Blade Designer and Manufacturer Fitness-for-Use
Many elements to the blade fabric FFU
Fabric
Handling
Molding
Performance
Mechanical
Performance
• Increased longitudinal content
• “Steerable” UD fabric
• Unrolling characteristic SPC
• Short layup cycle time
• Smooth and aligned layup
• Suitable ply termination
• Efficient Infusion process
• Process Consistency
• Part Quality Consistency
Fitness-for-Use Characteristics Product Development Trend
• Reliable cycle time
• Reliable glass content
• Reliable part thickness
• 0o Tensile Modulus & Strength
• 90o Tensile IFF (Inter-fiber Fracture)
• Reliable Fatigue performance
• Polyester blades
• 50 GPa Longitudinal Modulus
• 1200 MPa 0o static tensile strength
• Target IFF >90% matrix strength
• Fatigue target > 50% static @106
cycles
Case Study of High Modulus Glass Fabric
Case Study: Applicationof Ultrablade® TRIAX G3to Root Section
Ultrablade® TRIAX G3 fabric construction and modulus
Effect of fabric modulus on the blade root design
Infusion behavior
Wind Turbine Blade Root Connection Model (Samtech)
Single bolt and root laminate and bearing load modeled
Root Connection Simulation Results
High Modulus Ultrablade® TRIAX reduces axial bold
load by 17% which can increase bold fatigue life
Epoxy ResinInfusion Behavior
Area 9layers 19layers 29layers 39layers 49layers 59layers
Sample1-FWF 72.30% 72.20% 72.70% 72.80% 73.15% 73.38%
Sample2-FWF 72.35% 72.48% 72.52% 72.84% 72.98% 73.46%
Average FWF 0.72325 0.7234 0.7261 0.7282 0.73065 0.7342
Thickness 1.0998 1.0893 1.088 1.0882 1.0717 1.0716
Ultrablade® TRIAX Market Interest
Received first order. 350 root sections.
Published GL-certified independent testing reports
Summary
Independent laboratories confirm consistent and reliable results for main design properties (E, S, fatigue life) of current glass reinforcements and new products like WS3000 H-glass and Ultrablade® G3 fabrics. Similar linear best-fit slopes at higher initial static strength lead to longer life
Glass reinforcements continue to offer cost effective design solutions enabling longer and more efficient blades. We are pushing the UD glass/epoxy envelope, but we have not hit the upper limit
of glass blade length.
Ultrablade® G3 fabrics offer a cost-effective alternative to carbon
Since 2004, over 60 epoxy and polyester blades designs have been launched around the world using H-glass and Ultrablade®.
We expect design values of 50+GPa forHigh Modulus UD glass/epoxy.
Thank you
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