r.p.l. nijssen d.r.v. van delft l.g.j. janssen upwind: blade materials and structures european wind...
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R.P.L. NijssenR.P.L. Nijssen
D.R.V. van DelftD.R.V. van Delft
L.G.J. JanssenL.G.J. Janssen
UPWIND: Blade Materials and Structures
European Wind Energy Conference 2007European Wind Energy Conference 2007
Session: Structural Design and MaterialsSession: Structural Design and Materials
Thursday, May 10Thursday, May 10thth, 2007, 2007
WMC Knowledge Centre
Wind turbine Materials and Constructions
● History● Blade & Material testing for over 20 years
● Part of Delft University of Technology until 2003
● Activities● Full-scale wind turbine structural testing
● Material research
● Software Development
● Facilities● Flexible full-scale test laboratory
● Fatigue test machines
● Workshops
● Specimen production
● Projects (EZ/EU)● OPTIMAT
● INNWIND
● UPWIND
Wind turbine Materials & ConstructionsWind turbine Materials & Constructions
WMC Knowledge Centre
Wind turbine Materials and Constructions
Full Scale TestingFull Scale Testing
WMC Knowledge Centre
Wind turbine Materials and Constructions
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
Objectives: Reliable Optimal Use of Materials for Wind Turbine Rotor Blades
Period: 2002-2006Scientific Coordinator: WMC
Financial Coordinator: ECN
WMC Knowledge Centre
Wind turbine Materials and Constructions
Variable Amplitude Loading Establishment of reference S-N curves Comparison between CA and VA
Wisper spectrum Block tests
Establishment of new Wisper spectrum Influence load sequence1 Comparison of lifetime prediction for ECN/TUDT-Data with Wisper
- Mean Value -
0
50
100
150
200
250
300
350
100
Cycles
Str
es
s [
MP
a]
DLR: Linear MinerTUDT: LG log-logTUDT: LG lin-logTUDT: LG lin-log incl. R=0.1TUDT: alt lin-log R=0.1UP: Linear Miner, batch IUP: Non-Linr Miner, batch IUP: Linear Miner, batch IIWisper ECN, IWisper ECN, IIWisper TUDT, I
101 102 103 104 105 106
Results of various Lifetime Prediction Models
Variable Amplitude Loading Establishment of reference S-N curves Comparison between CA and VA
Wisper spectrum Block tests
Establishment of new Wisper spectrum Influence load sequence11 Comparison of lifetime prediction for ECN/TUDT-Data with Wisper
- Mean Value -
0
50
100
150
200
250
300
350
100
Cycles
Str
es
s [
MP
a]
DLR: Linear MinerTUDT: LG log-logTUDT: LG lin-logTUDT: LG lin-log incl. R=0.1TUDT: alt lin-log R=0.1UP: Linear Miner, batch IUP: Non-Linr Miner, batch IUP: Linear Miner, batch IIWisper ECN, IWisper ECN, IIWisper TUDT, I
101 102 103 104 105 106
Comparison of lifetime prediction for ECN/TUDT-Data with Wisper- Mean Value -
0
50
100
150
200
250
300
350
100
Cycles
Str
es
s [
MP
a]
DLR: Linear MinerTUDT: LG log-logTUDT: LG lin-logTUDT: LG lin-log incl. R=0.1TUDT: alt lin-log R=0.1UP: Linear Miner, batch IUP: Non-Linr Miner, batch IUP: Linear Miner, batch IIWisper ECN, IWisper ECN, IIWisper TUDT, I
DLR: Linear MinerTUDT: LG log-logTUDT: LG lin-logTUDT: LG lin-log incl. R=0.1TUDT: alt lin-log R=0.1UP: Linear Miner, batch IUP: Non-Linr Miner, batch IUP: Linear Miner, batch IIWisper ECN, IWisper ECN, IIWisper TUDT, I
DLR: Linear MinerTUDT: LG log-logTUDT: LG lin-logTUDT: LG lin-log incl. R=0.1TUDT: alt lin-log R=0.1UP: Linear Miner, batch IUP: Non-Linr Miner, batch IUP: Linear Miner, batch IIWisper ECN, IWisper ECN, IIWisper TUDT, I
101 102 103 104 105 106
Results of various Lifetime Prediction Models
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
Complex Stress State Checks on uni-axial and bi-axial tests Investigate beam model of rotor blade vs. shell
model for stress components Establish guidelines and safety factors for various
levels of sophistication in the design
2
Complex Stress State Checks on uni-axial and bi-axial tests Investigate beam model of rotor blade vs. shell
model for stress components Establish guidelines and safety factors for various
levels of sophistication in the design
22
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
Extreme Conditions Check influence of extreme conditions
T -40° and +60° Humidity
Identification of degradation parameters Phenomenological modelling and exp. determination
0.0005x 0.0025x
0xE
xiE 1xiE
x
[ / ]x mm mm
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
[ ]x MPa3
Degradation of Stiffness during Fatigue Life
Extreme Conditions Check influence of extreme conditions
T -40° and +60° Humidity
Identification of degradation parameters Phenomenological modelling and exp. determination
0.0005x 0.0025x
0xE
xiE 1xiE
x
[ / ]x mm mm
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
Loading curve of the GF/ EP [+452 -452]s
-20
0
20
40
60
80
100
120
140
160
0 0,005 0,01 0,015 0,02
x [mm/ mm]
x
[M
Pa]
Specimen CP451
[ ]x MPa33
Degradation of Stiffness during Fatigue Life
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
Thick Laminates & Repair Difference between thick and thin laminates
studied Material properties in thickness direction Measurements using embedded optical fibres Repair techniques Influence of brick and shell FE models
External patch
Filler
Scarf patch
Smooth or small steps
Parent structure
(A)
(B)
4
Plug/Patch and scarf repair systems FE analysis of the test specimen
Thick Laminates & Repair Difference between thick and thin laminates
studied Material properties in thickness direction Measurements using embedded optical fibres Repair techniques Influence of brick and shell FE models
External patch
Filler
Scarf patch
Smooth or small steps
Parent structure
(A)
(B)
44
Plug/Patch and scarf repair systems FE analysis of the test specimen
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
Residual Strength & Condition Assessment
Development of predictive model for residual strength reduction
Definition and validation of condition monitoring strategies for laminates in rotor blades
0.8·N3
N10.8·N1
0.2·N1
0.5·N1 N20.8·N2
0.2·N2
0.5·N2 N3
0.2·N3
0.5·N30
S
Log N 0.8·N3
N10.8·N1
0.2·N1
0.5·N1 N20.8·N2
0.2·N2
0.5·N2 N3
0.2·N3
0.5·N30
S
Log N
Stress levels for testing the residual strength after a percentage of the expected life
5
Residual Strength & Condition Assessment
Development of predictive model for residual strength reduction
Definition and validation of condition monitoring strategies for laminates in rotor blades
0.8·N3
N10.8·N1
0.2·N1
0.5·N1 N20.8·N2
0.2·N2
0.5·N2 N3
0.2·N3
0.5·N30
S
Log N 0.8·N3
N10.8·N1
0.2·N1
0.5·N1 N20.8·N2
0.2·N2
0.5·N2 N3
0.2·N3
0.5·N30
S
Log N
Stress levels for testing the residual strength after a percentage of the expected life
55
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
Improved Design Recommendations
Task group leaders and certification bodies
State-of-the-art analysis of results using resultsof the task groups 1 to 5
Based on consistent set of tests
Interaction effects also covered
Basis for future design guidelines
6
Improved Design Recommendations
Task group leaders and certification bodies
State-of-the-art analysis of results using resultsof the task groups 1 to 5
Based on consistent set of tests
Interaction effects also covered
Basis for future design guidelines
66
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
VariableAmplitude
Residual strength and
Condition MonitoringComplex
Stressstates
Extremeconditions
Thick LaminatesandRepair
Material ResearchEU Project: Optimat Blades
Material ResearchEU Project: Optimat Blades
WMC Knowledge Centre
Wind turbine Materials and Constructions
OPTIDATOPTIDAT
0
5000
10000
15000
20000
25000
30000
35000
40000
45000
prior t
o 02-O
ct-0
3
02-Oct
-03
22-Oct
-03
31-Oct
-03
13-Nov-
03
14-Nov-
03
28-Nov-
03
26-Feb-0
4
12-May-
04
17-May-
04
25-May-
04
27-May-
04
09-Jun-0
4
11-J
un-04
18-Jun-0
4
18-Oct
-04
20-Dec-
04
04-Jan-0
5
14-Jan-0
5
28-Jan-0
5
04-Feb-0
5
12-Apr-0
5
28-Apr-0
5
23-Jun-0
5
01-Jul-0
5
08-Sep-0
5
19-Oct
-05
29-Nov-
05
12-Dec-
05
19-Jan-0
6
09-Feb-0
6
WMC DLR RAL RISØ CRES VUB UP VTT
Totals
18286
51411587 3884
17551673
7028
526
Tes
tin
g t
ime
[h
]
Total: 39880
Available via: www.wmc.eu
WMC Knowledge Centre
Wind turbine Materials and Constructions
Lessons learnt from Optimat BladesLessons learnt from Optimat Blades
● Plate-to-plate and lab-to-lab variations are important in a project of this size● Minor Tg and Vf variationssignificant performance variations?
● Some plates worse in static strength, better in fatigue● Machine-to-machine● Environmental conditions● Sometimes larger than investigated influences ● More realistic assessment of scatter● Preferably: production of all specimens first, then mix and send
out (not possible in practice)
● Establishing an alternative test geometry is difficult● People perceive standards automatically as “better” even when
no background info is provided● Universal geometry is compromise…OK for consistency(?)
WMC Knowledge Centre
Wind turbine Materials and Constructions
Topics for UPWIND WP 3.1Topics for UPWIND WP 3.1
WP 3.1: Tests and phenomenological modeling
WP 3.2: Micro/Meso-mechanical model
WP 3.3: Damage tolerant design
WP 3.1: Tests and phenomenological modeling
WP 3.2: Micro/Meso-mechanical model
WP 3.3: Damage tolerant design
WMC Knowledge Centre
Wind turbine Materials and Constructions
Topics for UPWIND WP 3.1Topics for UPWIND WP 3.1
● Static strength, especially compression
● Constant Life Diagram, especially concentrating on higher number of cycles
● Bi-axial stress states
● Extreme (climatic) conditions as well as influence of the frequency on fatigue test results
● Behaviour of thick and repaired laminates
● Damping
● Life cycle analysis
● Extension with new materials of the public material database OPTIDAT
● www.wmc.eu
WMC Knowledge Centre
Wind turbine Materials and Constructions
Partners WP 3.1Partners WP 3.1
● RISØ
● ECN
● WMC
● CRES
● UP
● GE
● FIBERBLADE
● VTT
● CCLRC
● VUB
WMC Knowledge Centre
Wind turbine Materials and Constructions
Advantages
● Fits measurement equipment
● Eliminate geometry effects
● Flexibility (progressing insights during long-term project…)
● Combined tests, e.g. residual strength
Disadvantages
● Poorer compression characteristics than
ISO/ASTM
● Static● Compression-compression fatigue tests● Buckling (test machine dependent,
elevated temperatures, after fatigue damage)
Universal test geometryUniversal test geometry
WMC Knowledge Centre
Wind turbine Materials and Constructions
Preliminary programmePreliminary programme
● Reference material● Glass Epoxy, delivered by GE
● WMC can also make their own plates
● Layouts
● Embedded sensors
● Study of several rectangular geometries for 4 and 6 layer lay-ups tested in preliminary programme● Free length
● Width
● Tab thickness: from 0 to 2 mm
● Static and zero-mean stress (R= -1) fatigue
WMC Knowledge Centre
Wind turbine Materials and Constructions
First test results (R=-1 fatigue)First test results (R=-1 fatigue)
1.4
1.2
1
0.8
0.6
0.4107106105104103102101100
Cycles to failure
[%
] R08, tab:1 (AK&AQ)
R08, tab:0.5mm (AP)
R07, tab:1mm (AS)
R07, tab:0.5mm (AM)
R17, tab:0mm (AL)
R03, tab:1mm (AN)
R03 (OPTIMAT UD)
R06, tab:2 (OB)mm (AK)
WMC Knowledge Centre
Wind turbine Materials and Constructions
CompressionCompression
● Approach Compression
● Risø set-up (RISØ)
● ISO (WMC)
● Combined loading (WMC)
● Test short OPTIMAT (WMC/UP/CRES)
● Standard OPTIMAT as reference (WMC/UP/CRES)
● Compression test University of Dresden (GE)
● VUB will look at the full optical field for compression
● Objectives
● New geometry for static compression
● Fatigue geometries for R=-1 and R=10
WMC Knowledge Centre
Wind turbine Materials and Constructions
Ageing & FatigueAgeing & Fatigue
● Problem: initial fatigue results within OPTIMAT BLADES ● Lower than expected
● Required lower frequencies
● Is it only temperature or other effects as well?● Check at various frequencies and temperatures
● Check fatigue behaviour at elevated temperatures and high humidity levels
WMC Knowledge Centre
Wind turbine Materials and Constructions
100
150
200
250
300
350
400
1 10 100 1000 10000 100000
Sequences to failure
Sm
ax
WISPER data
Multiple R-ratio (6 R-ratios)Single R; R=0.1
Linear GoodmanShifted Goodman
0
100
200
300
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [
MP
a]
103 Cycles
106 Cycles
109 Cycles
0
100
200
300
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [
MP
a]
103 Cycles
106 Cycles
109 Cycles
0
100
200
300
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [
MP
a]
103 Cycles
106 Cycles
109 Cycles
0
100
200
300
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [
MP
a]
103 Cycles
106 Cycles
109 Cycles
30% unconservative
2000% unconservative
Constant Life Diagram (CLD)Constant Life Diagram (CLD)
WMC Knowledge Centre
Wind turbine Materials and Constructions
0
50
100
150
200
250
300
350
400
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [M
Pa]
0
50
100
150
200
250
300
350
400
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [M
Pa]
R=-0.4
R=0.5
R=0.1R=10
R=-2.5
R=-1● Linear Goodman Diagram: poor performance
● Development of comprehensive CLD formulation (based on regression through multiple R-values)
● Ideally: Static strength + few tests determine fatigue behaviour
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
-300.0 -200.0 -100.0 0.0 100.0 200.0 300.0 400.0m [M Pa]
a [M
Pa]
100
1000
1E+04
1E+05
1E+06
1E+07
1E+08
Static limit
CLD…modellingCLD…modelling
WMC Knowledge Centre
Wind turbine Materials and Constructions
CLD…Long life tests (>106)CLD…Long life tests (>106)
● Verify S-N curve extrapolations
● Duration typically 1 month….+ scatter!
0
50
100
150
200
250
300
350
400
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [M
Pa]
0
50
100
150
200
250
300
350
400
-600 -400 -200 0 200 400 600
Smean [MPa]
Sam
p [M
Pa]
Most data available here
Most ‘real-life’ loads here
R=-0.4
R=0.5
R=0.1
R=10
R=-2.5R=-1
WMC Knowledge Centre
Wind turbine Materials and Constructions
Thick LaminatesThick Laminates
Static and Fatigue results
100
1000
1 10 100 1000 10000 100000 1000000 10000000 100000000
No. of cycles
max
Thin specimens
Thick specimens
Series3
Series4
Power (Thinspecimens)Power (Thickspecimens)
WMC Knowledge Centre
Wind turbine Materials and Constructions
Circle of lifeCircle of life
WMC Knowledge Centre
Wind turbine Materials and Constructions
Missing link?Missing link?
WMC Knowledge Centre
Wind turbine Materials and Constructions
Subcomponent TestingSubcomponent Testing
●Geometry used up to now: essentially 1D●No sidewise support
●Conservative estimation
●Not actually repaired but scarf connection●Same quality?
●New geometry for 2D tests ●Axial or 4-point Bending
●Repairs and/or buckling
●Glue and glue repairs
●Or double C instead of I-beam
●Or Glue connection
●Sandwiches
●Blade part: UD + web
WMC Knowledge Centre
Wind turbine Materials and Constructions
EndEnd
● Thank you!
● Questions/comments/discussion…?
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
-300.0 -200.0 -100.0 0.0 100.0 200.0 300.0 400.0m [M Pa]
a [M
Pa]
100
1000
1E+04
1E+05
1E+06
1E+07
1E+08
Static limit
0
5000
10000
15000
20000
25000
30000
35000
40000
45000WMC DLR RAL RISØ CRES VUB UP VTT
Totals
18286
51411587 3884
17551673
7028
526
Testi
ng
tim
e [
h] Total: 39880
WMC Knowledge Centre
Wind turbine Materials and Constructions
Session QuestionsSession Questions
● What advances in methods for the design analysis of wind turbine structural components will be adopted by the industry over the next 5-10 years? What benefits will these advances bring?
● Is the full scale testing of blades and other wind turbine components likely to become more or less important in the future?
● Does the introduction of probabilistic approaches to wind turbine design calculations result in more optimised structural components, more conservatism, or more uncertainty?
● Is it likely that adaptive blades will ever replace pitch regulated blades?