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.
The influence of using carbon nanotubes to improve bond strength between textiles reinforced mortar and concrete was investigated. Forty-two specimens were tested using double-shear test to evaluate the effect of various parameters such as CNTs addition, type of textile material, bond length and width, and number of TRM layers on the bond behavior. Two types of textile: carbon and basalt fibers were used. Various bond length and width including 50 mm, 100 mm, and 150 mm were considered. Three different percentages of CNTs; 0.05%, 0.1%, and 0.2% by weight of cement, were used. The effect of CNTs addition on the mechanical strength of cement mortar and pull-off strength of TRM were also investigated. Test results showed that adding small amount of CNTs enhanced the tensile and flexural strength of cement mortar, the pull-off strength of the TRM, and the ultimate bond load between the TRM and concrete substrate. The ultimate bond load was highly dependent on the amount of added CNTs, type of textile material, geometry of the bonded area, and number of TRM layers. The SEM images showed the role of the CNTs to enhance the adhesion at the fiber-matrix interface.
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