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Fiber reinforced polymer (FRP) composite materials have been used in a variety of civil and infrastructure applications since the early1980s, including in wind turbine blades. The world is now confronting the problem of how to dispose of decommissioned blades in an environmentally sustainable manner. One proposed solution is to repurpose the blades for use in new structures. One promising repurposing application is in pedestrian and cycle bridges. This paper reports on the characterization of a 13.4-m long FRP wind blade manufactured by LM Windpower (Kolding, Demark) in 1994. Two blades of this type were used as girders for a pedestrian bridge on a greenway (walking and biking trail) in Cork, Ireland. The as-received geometric, material, and structural properties of the 27 year-old blade were obtained for use in the structural design of the bridge. The material tests included physical (volume fraction and laminate architecture) and mechanical (tension and compression) tests at multiple locations. Full-scale flexural testing of a 4-m long section of the blade between 7 and 11 m from the root of the blade was performed to determine the load-deflection behavior, ultimate capacity, strain history, and failure modes when loaded to failure. Key details of the testing and the results are provided. The results of the testing revealed that the FRP material is still in excellent condition and that the blade has the strength and stiffness in flexure to serve as a girder for the bridge constructed.
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Higher-order moment stability of large wind turbine blades under stochastic perturbations
The current trend in offshore wind energy is to design and install systems with larger swept areas that yield unprecedented efficiency. Long and slender blades are needed to achieve this objective. As a result of aerodynamic and structural tailoring, slender blades are particularly susceptible to various dynamic instability phenomena during standard operations. One of these phenomena is the bending-torsion flutter that may lead either to structural failure or system breakdown. The research author has been examining blade flutter under the influence of stochastic perturbations, which include both flow turbulence and aeroelastic load variability. A reduced-order Markov model has been used to describe the effects of the various random perturbations. Mean-square stability has been recently explored; results suggest that perturbations may negatively impact the flutter angular speed and increase the risk of failure. In this study the model is employed to investigate moment stability beyond mean squares, observing that dynamic instability involves nonlinear propagation of the perturbations and may exhibit amplitude dependency. Third-order instability is investigated and compared against previous numerical results. The NREL 5MW reference wind turbine blade is used as a benchmark example.
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- Award ID(s):
- 2020063
- PAR ID:
- 10532195
- Publisher / Repository:
- IOP Science
- Date Published:
- Journal Name:
- Journal of Physics: Conference Series
- Volume:
- 2647
- Issue:
- 11
- ISSN:
- 1742-6588
- Page Range / eLocation ID:
- 112001
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1088/1742-6596/2647/11/112001
