Engineering and Construction Torsional Responses of Glass-Fiber/Epoxy Composite Blade Shaft for A small Wind Turbine

Abstract

Recently, composites made of thermosetting epoxy matrix reinforced by glass fibers have been widely used for advanced engineering and aerospace applications. This study newly proposes a developed methodology to manufacture a glass-fiber/epoxy resin composite blade of a small 1kW wind generator system. The improved mechanical properties of the composite blade are verified in a series of systematic experiments. The study focuses on the responses of applying a torsional loading to a long straight member such as the root of the composite blade. The core aluminum shaft was wrapped in glass-fiber/epoxy to form the root of the composite blade and a composite shaft. The composite shaft is a sandwich structure combining glass-fiber/epoxy and an aluminum shaft. The composite shaft was placed in a torsional testing machine and a strain gage monitored the strain on the composite shaft. We considered the composite blade to have a circular cross section and determined both stress distribution within the member and the angle of twist. Finally, mechanical properties were obtained in torsional testing, including the relationship between applied torque and the angle of twist on the composite shaft. The torsional loading and failure locations of the blade root were measured experimentally. The experiments showed that the weakest location of the blade root is at the interface of the aluminum shaft and glass-fiber/epoxy lay-ups in the composite blade root. It is found that the quality of the aluminum shaft, the glass-fiber/epoxy layers around the shaft and the bonding at the interface between the shaft and the layers should be increased to improve the torsional strength of the composite blade. These results can provide a reference for analysts and designers of small wind turbine systems.