Researchers at UC Davis are using the unique properties of carbon nanotubes to create strong and multifunctional coatings that can be sprayed onto any surface and monitor changes occurring in the structure. The coating is sensitive to strain in the sense that if you pull or push on it, the electrical properties change depending on how much deformation occurs. The carbon nanotubes are sprayed onto the desired surface and electrodes are attached around the boundaries of the coating. The overarching goal of this research is to derive a structural health monitoring and failure prognosis method that is applicable to wind turbine structures. By using the test wind turbine on the roof of Bainer Hall and a prototype wireless sensor monitoring sensor system, the scientists will devise an early-warning structural health monitoring system that will warn operators when damage to turbine blades poses a risk of structural failure.
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UC Davis engineering professors Ken Loh and Valeria La Saponara use the unique properties offered by tiny carbon nanotubes to make multifunctional coatings that can monitor damage forming in significant structures like bridges and wind turbines. The nanotubes can be fabricated into structural coatings using a technique called layer-by-layer assembly to lay down the nanotubes one layer at a time. The resulting sheet of material is sensitive to strain in the sense that if you pull or push on it, the electrical properties change depending on how much deformation occurs. The assembly process has been improved where the carbon nanotubes can now be sprayed onto the desired surface and electrodes are attached around the boundaries of the film.
The goal of their current CITRIS research is to find a way to monitor the structural health of wind turbine blades and tower and then to determine whether they will fail before they actually do so. Specifically, the research activities will validate an in situ sensing technology for damage detection in composite materials (such as the wind blade), utilize experimental data for updating numerical models, and characterize structural demand for failure prognosis of critical elements within wind turbine structures.
The study will embed thin films capable of spatial strain sensing in fiber-reinforced composites for detecting localized damage at critical hotspots within the blade structure. Instrumented scaled wind turbine blades will be tested in the lab under static and dynamic load configurations. Subsequently, data from full-scale field studies will be obtained using an existing wind turbine test bed at the University of California-Davis campus.
This project will lead to early-warning structural health monitoring systems that will warn operators when damage to turbine blades poses a risk of structural failure. This project integrates and advances disparate fields of composite structures, aero-elastic structure interaction theory, structural dynamics, and nanotechnology-based sensor applications.
L. P. Mortensen, D. Ryu, Y. Zhao, and K. J. Loh, 2013, “Rapid Assembly of Multifunctional Thin Film Sensors for Wind Turbine Blade Monitoring,” Key Engineering Materials Journal (1013-9826), Trans Tech, 569-570: 515-522. [DAMAS Best Paper Award]
B. R. Loyola, V. La Saponara, K. J. Loh, T. M. Briggs, G. O’Bryan, and J. L. Skinner, 2013, “Spatial Sensing using Electrical Impedance Tomography,” IEEE Sensors (1530-437X), IEEE, 13(6): 2357-2367.
B. R. Loyola, T. M. Briggs, L. Arronche, K. J. Loh, V. La Saponara, G. O’Bryan, and J. L. Skinner, 2013, “Detection of Spatially Distributed Damage in Fiber-Reinforced Polymer Composites,” Structural Health Monitoring (1475-9217), Sage, 12(3): 225-240.
B. R. Loyola, L. Arronche, M. LaFord, V. La Saponara, and K. J. Loh, “Evaluation of the Damage Detection Characteristics of Electrical Impedance Tomography,” Proceedings of the ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Snowbird, UT, September 16-18, 2013.
B. R. Loyola, K. J. Loh, V. La Saponara, J. C. Chen, and T. M. Briggs, “Comparative Study of Non-destructive Damage Evaluation Methodologies for CFRP Low Velocity Impact Damage,” Proceedings of SAMPE TECH 2012, Charleston, SC, October 22-25, 2012.