Edam Meeting Template v2
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Transcript of Edam Meeting Template v2
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Optimization of composite bonded joints andrepairs
Maria Victoria Castro FernndezEDAM focus area (MIT-Portugal)Faculty of Engineering, University of Porto
Supervisor: Marcelo Moura
Co-Supervisors: Antonio Torres Marques, Lucas Silva, Thomas Eager& Manuel Freitas
EDAM Meeting FEUP
Porto, March 16, 2011
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Objectives
The use of fracture mechanics in designing againstdamage propagation;
Create methodologies to conduct bonded
joints/repairs in structures of compositesmaterials;
Development of systems to teach technicians and
shop-floor workers how to optimize the costs andbonding performance in structures currently used
in industry.
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Assessed Needs
Better understanding of bonded
joints behavior, to develop anindustry with enough knowledge
to design structures;
Impact of the repairs and qualitycontrol in the durability of the
blades;
Critical costs when a wind turbinehas stop for maintenance.
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Main Tasks
Fatigue characterization of bonded joints
Evaluation of geometrical changes effects on
bonds fatigue strength
Cost analysis
Manufacture
Non-destructive testing
Durability
Methodology Development
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Time-line of the main tasks
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FATIGUE CHARACTERIZATION
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Main Tasks
Fatigue characterization of bonded joints undermode I, mode II and mixed-mode loading:
Mode I: DCB (Double Cantilever Beam)
Mode II: ENF (End Notched Flexure)
3 points Mixed mode: still define the possible test
ELS-MM End Loaded Split for Mixed-Mode;
SLB (Single-Leg Bending).
Variables: Determination of Paris law parameters
and fracture surfaces characterization.
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Introduction
Cyclical fatigue loading leads to failure even at small loads.
For fatigue damage two approaches have been used extensively - stress-life andfatigue crack growth (FCG).
The FCG method is the correlation between the rate of fatigue crack growth per
cycle (da/dN) and the change of one fracture parameter (G Energy Release
Rate) over the time.
The Paris-Law is an empirical law.
2
1
C
I
Ic
GdaC
dN G
Paris-Law
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Experimental tests
The ASTM E 647 08 standard was used
The tests were made with load control (constant
amplitude loading).
The load ratio (R) is 0.1 and the maximum load is50% of the average maximum static load.
The main objective of these tests is to define the
fatigue crack growth rate as a function of the
(Gmax/Gic (i=I,II))
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)1(' 2
aa
E
EE
E
tha '634
2
222
)1(22
bEI
aP
da
dC
b
PG
I
Data reduction scheme to evaluate GI =f(ae)
Pirondismethod:
CBBM:
2 3
1 2 3 4C A A a A a A a
da
dC
b
PG
I
2
2
ef ( )a C
32
3
2221
'
2aaa
bE
t
PC
a
Polynomial:
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Experimental tests
Double Cantilever Beam
End-Notched Flexure
Both tests have equivalent dimensions,
because the Paris-law depends on the
specimen geometry.
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Specimens
DCB
L = 125 mm
a0 = 45 mm b= 25 mm
l3= 15 mm
h = 2.7 mm
ENF
L = 125 mm
a0
= 45 mm
b= 25 mm
h = 2.7 mm
The adhesive thickness is 0.2 mm
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DCB Results
y = 0.0156x2.9155R = 0.9446
0.0001
0.001
0.01
0.1 1
dae/dN
GImax/GIc
dae/dN
Power(dae/dN)
100
150
200
250
300
350
400
40 50 60 70 80
G
Imax
(J/mm2)
a (mm)
G CBBM
GmaxPirondi
40
80
120
1000 11000 21000 31000
a(
mm)
N (nmero de ciclos)
ae
a medido
0.0005
0.005
0.2
da/d
N
GImax/GIc
da/dN (Pirondi)
dae/dN (CBBM)
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DCB Results
Ysec = 0,0196x3,2675R = 0,6644
Ypol = 0,0055x2,29R = 0,8019
0.0001
0.001
0.010.2
dae
/dN
GImax/GIc
Lei Geral (secante)
Lei Geral (pol)
Power (Lei Geral(secante))
Power (Lei Geral(pol))
General Law 0,0055 2,29Polynomial Method
2
1
C
I
Ic
GdaC
dN G
General Law 0.0196 3.26747Secant Method
Paris law constants
C1 C2
1 0.0255 3.2702
2 0.0156 2.9155
3 0.1226 5.0217
4 0.1837 4.9585
5 0.0163 3.62376 0.014 2.7019
C1 C2
1 0,0078 2,3391
2 0,0048 2,161
3 0,0059 2,4042
40,0063 2,0792
5 0,007 3,0529
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ENF Results
A Matlab program was made to calculate the
displacement, the load and the compliance of the
specimen by using the real time acquisition data
of the MTS machine.
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ENF Results
0
0.5
1
1.5
2
2.5
3
0
0.001
0.002
0.003
0.004
0.005
0.006
0.007
0 50000 100000 150000
G
ii
C
N (Number of Cycles)
C
G CBBM
-1200
-1000
-800
-600
-400
-200
049 49.5 50 50.5 51 51.5 52 52.5
Load(N)
Time (s)
y = 0.0686x2.9697R = 0.6022
y = 0.2242x3.804R = 0.7765
y = 0.0344x3.0875R = 0.8856
0.00001
0.0001
0.001
0.01
0.1
11.00E-01 1.00E+00
dae/dN
Giimax/Giic
Specimen 1
Specimen 2
Spec. 1 Pol. Method
Power (Specimen 1)
Power (Specimen 2)
Power (Spec. 1 Pol.Method)
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INTRODUCTION TO THE WINDINDUSTRY
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Wind Industry
There some projects to develop more efficient methods to
build the eolic blades.The demand for blades has become larger in the last
years.
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Blades
1
2
3
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BLADES
All the structure is bonded.
The adhesive joints are critical points in the bladestructure;
The repairs are performed by bonding patches
Fatigue behavior is crucial in these structures
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COSTS ANALYSIS
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Manufacturing
Manufacturing costs and weight saving:
In 8 ton, 1 ton approximately is from the adhesive.
Durability:
Less maintenance of the blades in situ.
Quality of the bonded joints:
Infrared (IR) scanning
Ultrasounds
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Manufacture
i) Make an impact evaluation of the adhesive cost in the
cost of the blade Variables: costs involved in manufacturing the blade and costs
involved in the bonding.
ii) Optimization of the bonding process by reducing the
time, raw materials and costs
Variables: Time of bonding and amount of adhesive used.
iii) Quantify the costs reduction and the impact in the
cost of the blade Variables: costs related to the improvements proposed in ii).
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Non-Destructive testing
Define the most appropriate methodology for the
quality control of the blades, the costs ofimplementing this technology and the
advantages.
Variables: most important parameters, costs ofimplementing the selected technology and the main
advantages.
Possible methodologies to define the technology:
SWOT analysis
Weight matrix for the most important parameters.
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Methodology Development
Develop a cost-effective bonded process for
implementation in the wind energy industry.
Variables: create a methodology to manufacture blades with
optimized bonded joints.
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Conclusions