screening tests of composites for use in tidal energy devices anderson ogg master thesis committee...
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Screening Tests of Composites for Use in Tidal Energy DevicesAnderson Ogg
Master Thesis
Committee Members:
Mark Tuttle - Chair
Brian Fabian
Brian Polagye
Tidal Energy
In this context, tidal energy refers to the use of hydrokinetic devices, such as turbines, to extract energy from the water flow created by the changing of the tides.
Some Advantages:• Sustainable• Predictable - Base Load Power
Overall Goal
To provide device developers with useful information that
enables them to make more informed design tradeoff
decisions.
Why Composites?
• Large rotational surfaces – Weight will be important
• Lack of information in the public domain
• Potential maintenance advantages• May not need to preserve (paint)• May be less susceptible to biofouling
GFRE
GFRV
Pre-Preg
CFRE
Materials Chosen• Glass Fiber Reinforced Epoxy – GFRE
• Carbon Fiber Reinforced Epoxy – CFRE
• Pre-Impregnated Carbon Fiber – Pre-Preg
• Glass Fiber Reinforced Vinylester – GFRV
A Quick Review• Stress is force divided by area (F/A)
• A shear force acts tangent to a surface
• Shear Stress is the shear force divided by area (V/A)
• Strain is the change in length divided by the original length
• Shear Strain is the change in angle
From Professor Tuttle’s ME 556 Review of Concepts Presentation
From Professor Tuttle’s ME 556 Review of Concepts Presentation
Why Shear Modulus?• Just a screening test
• Changes in strength and stiffness properties were expected to be primarily caused by changes in the matrix
• The shear modulus is a matrix dominated property
• After determining the longitudinal and transverse strain, you can calculate the shear strain and shear modulus
• ASTM standard D3518 “Standard Test Method for In-Plane Shear Response of Polymer Matrix Composite Materials by Tensile Test of a ±45° Laminate.”
0 0.005 0.01 0.015 0.02 0.025 0.030.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
50.00
Specimen G3 Shear Stress v. Shear Strain
Stress v. Strain Curve
Shear Strain (radians)
Sh
ea
r S
res
s (
MP
A)
Experiment Plan• As-produced
• In situ exposure
• Accelerated exposure
• Weight monitoring
• Changes in shear modulus
• Optical microscopy
In Situ Experimental Setup• One panel of each system kept at the UW in a as-
produced condition
• Two panels of each system placed on NNMREC’s Sea Spider
• One panel of each system removed after 9 months
• One panel of each system is still on the Sea Spider and should be removed after 18 months (November 2011)
SS Location at Admiralty Inlet
Accelerated Experimental Setup• Chose to only use the GFRV system
• 3 panels, each subjected to one month exposure in heated artificial seawater at 30, 40 and 50˚C
• Similar techniques used throughout the literature.
• Continuous weight monitoring
Specimen Construction
Testing Procedures
Data Collection Example
SpecimenShear Modulus
Slope (GPa)
D1 2.51
D2 2.45
D3 2.51
D4 2.40
B1 0.84
B2 0.81
B3 0.77
B4 0.92
Results• Shear Modulus
• Weight Gain
• Microscopy
• Biofouling
Shear Modulus Results
Panel
Shear Modulus Change (GPa)
Standard Deviation
(GPa)
Coefficient of Variation Percent Loss
GFRE 1.63 0.08 5% 66%
CFRE 0.88 0.10 12% 26%
Pre-Preg 0.28 0.09 32% 7%
GFRV 0.29 0.07 24% 13%
GFRV @ 30 0.84 0.15 17% 38%
GFRV @ 40 0.73 0.08 11% 33%
GFRV @ 50 0.74 0.09 12% 33%
GFRE (D and B) CFRE (G and E) Pre Preg (T and U) GFRV (Y,M,Q,R and X)0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
Shear Modulus of All Panels
As Produced
Exposed 9 Months
30˚C
40˚C
50˚C
Material System
Me
an
Sh
ea
r M
od
ulu
s (
GP
a)
SystemPanel
Pre PregGRFEGFRVCFREUTDBYMGE
4
3
2
1
0
Shear
Modulu
s (G
Pa)
95% CI for the MeanInterval Plot of Shear Modulus for In Situ Panels
0.40.30.20.10.0
X_
Ho
Differences
Boxplot of Differences for Panels T and U(with Ho and 95% t-confidence interval for the mean)
SystemPanel
GFRVYXRQM
2.5
2.0
1.5
1.0
0.5
0.0
Shear
Modulu
s (G
Pa)
95% CI for the MeanInterval Plot of Shear Modulus for GFRV
0.20.10.0-0.1-0.2-0.3-0.4
X_
Ho
Differences
Boxplot of Differences for Panels Q and R(with Ho and 95% t-confidence interval for the mean)
Weight Gain of In Situ Panels
Panel SystemInitial weight
(grams)
Weight with biofouling
±.05 (grams)
Weight after biofouling removed (grams)**
Weight after drying
(grams)
Difference between
initial and final (grams)
Percent change
B GFRE 154.08 194.15 164.91 164.34 10.26 6.24%
E CFRE 128.11 154.7 133.64 132.23 4.12 3.12%
U Pre-Preg 157.64 160.45 158.44 158.39 0.75 0.47%
M GFRV 150.96 219.98 159.95 157.11 6.15 3.91%
1/7/
2011
1/12
/201
1
1/17
/201
1
1/22
/201
1
1/27
/201
1
2/1/
2011
2/6/
2011
74.4
74.6
74.8
75
75.2
75.4
75.6
75.8
76
76.2
76.4
740.0
745.0
750.0
755.0
760.0
765.0
770.0
775.0
780.0
GFRV @ 30˚C (Panel Q) Weight Change
Scale Weight
Barometric Pressure
Date
Sc
ale
We
igh
t (g
ram
s)
Pre
ss
ure
(m
m o
f m
erc
ury
)
Weight Gain of Accelerated PanelsPanel
Exposure Temperature (˚C)
Initial Weight (grams)
Final Weight (grams)
Weight Difference (grams)
Percent Change
Q 30 191.90 192.77 0.87 0.45%
R 40 193.29 194.23 0.94 0.48%
X 50 188.67 190.01 1.34 0.71%
PanelExposure
Temperature (˚C)
Initial Weight Shown on
Balance (grams)
Final Weight Shown on
Balance (grams)
Weight Difference (grams)
Percent Change
Q 30 75.04 76.13 1.09 1.43%
R 40 136.74 137.92** 1.18 0.86%
X 50 69.52 73.38 3.86 5.26%
Microscopy
GFRE Panels D and B
CFRE Panels G and E
Biofouling
Barnacle Removal
Flake Off at About 2% Shear Strain
Conclusions• The GFRV system was the least expensive and had the
second best performance
• From the literature, it was expected that the GFRV would absorb less moisture but that the epoxy based systems would perform better; these were not the results obtained in the experiment
• Depending on weight tradeoffs, the GFRV system may be perfectly acceptable for use in tidal energy devices.
• Biofouling had little effect
• Accelerated testing results need to be used with caution
Differences in B and D
Voids
Future Work• Further examination into the mechanism that caused such
a change in the GFRE system
• Remove the 18 month panels in November and test them
• When does the loss of shear modulus level out?
Acknowledgements• Mariette• Bill and Tuesday Kuykendall• My Committee and Professors• Fellow Graduate Students• U.S. Coast Guard
Questions?
Extra Material