Presentation on theme: "Screening Tests of Composites for Use in Tidal Energy Devices Anderson Ogg Master Thesis Committee Members: Mark Tuttle - Chair Brian Fabian Brian Polagye."— Presentation transcript:
Screening Tests of Composites for Use in Tidal Energy Devices Anderson 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
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 Tuttles 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.
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 NNMRECs 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
Data Collection Example Specimen Shear Modulus Slope (GPa) D12.51 D22.45 D32.51 D42.40 B10.84 B20.81 B30.77 B40.92
Results Shear Modulus Weight Gain Microscopy Biofouling
Shear Modulus Results Panel Shear Modulus Change (GPa) Standard Deviation (GPa) Coefficient of Variation Percent Loss GFRE %66% CFRE %26% Pre-Preg %7% GFRV %13% %38% %33% %33%
Weight Gain of In Situ Panels PanelSystem Initial weight (grams) Weight with biofouling ±.05 (grams) Weight after biofouling removed (grams)** Weight after drying (grams) Difference between initial and final (grams) Percent change BGFRE % ECFRE % UPre-Preg % MGFRV %
Weight Gain of Accelerated Panels Panel Exposure Temperature (˚C) Initial Weight (grams) Final Weight (grams) Weight Difference (grams) Percent Change Q % R % X % Panel Exposure Temperature (˚C) Initial Weight Shown on Balance (grams) Final Weight Shown on Balance (grams) Weight Difference (grams) Percent Change Q % R ** % X %
GFRE Panels D and B
CFRE Panels G and E
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