Abstract
Wind power is an inevitable green power in the world and Taiwan in this century, especially at Hsinchu where is called as “Wind City”. The conventional horizontal-axis wind turbine has some disadvantages such as noise, requirement of stable wind field, vast location, etc. The investigation of material properties for blade of the low-power, small space and random-wind-directional power generating vertical-axis wind turbine is a major job in this study. Furthermore, the light-weight and high-strength composite adopted to fabricate wind turbine instead of lated metal materials is also researched in this study. Carbon nanotubes (CNTs) possess special physical characteristics such as strength, stiffness, light weight, electrical conductivity, highly thermal conductivity and thermal stability, etc. Meanwhile, there is a lot of potential applications such as the aviation, aerospace, electromagnetic interference (EMI) material and electrostatic discharge (ESD), etc. In this research, study of composites composed of multi-wall carbon nanotubes (MWCNTs) as reinforcement and epoxy resin as matrix of laminate for fabricating wind turbine was focused on influence on the static mechanical properties and dynamic torsion fatigue behavior on blade for vertical-axis wind turbine. Additionally, the effect of adding different proportions of MWCNTs of MWCNTs-containing composites on static mechanical properties and dynamic torsion fatigue life was also investigated. And observe the resistant ability of laminates composite treated to various temperatures, humidities and thermal cycles. Finally, morphologies for the fracture surface of laminates composite are observed by thermal emission schottky field scanning electrical microscopy (TFSEM). In this study, MWCNTs were spread evenly among epoxy resin by using high-efficiency ultrasonication, and MWCNTs were infused into EPO-622 epoxy resin adopting sonic cavitation and high-speed mechanical stirring. Finally, the residual air bubbles were removed using vacuum technique. Flexural, interlaminar shear strength (ILSS), torsion strength and torsion fatigue tests were performed on MWCNTs-filled (0.5wt%, 1.0wt% and 1.5wt% by epoxy resin weight) epoxy resin composites and MWCNTs-unfilled composites to identify the effect of adding MWCNTs on the mechanical properties of carbon fabric-epoxy resin composite. Woven carbon fiber and epoxy resin were adopted to fabricate composite using hot press molding. The highest improvement in static mechanical properties and dynamic torsion fatigue life was obtained when amount of MWCNTs of MWCNTs-containing composite reached to 1.5wt%. Flexural, interlaminar shear stress, torsion and torsion fatigue tests were performed to evaluate the effectiveness of MWCNTs addition on the mechanical properties and fatigue life of the carbon fabric-epoxy resin composite. The flexural strength and flexural modulus of the 1.5wt% MWCNTs-containing composite improved by 8.97% and 11.45%, respectively, compared to that of the composite without MWCNTs. Moreover, the 1.5wt% MWCNTs-containing carbon fabric-epoxy composite showed 10.74% enhancement on the interlaminar shear stress compared to that of composite without MWCNTs. Based on the experimental result, a linear damage model has been fitted with ordinary least squares (OLS) method for unfilled and MWCNTs-filled carbon fabric-epoxy composite. Additionally, the torsion fatigue lift was also improved significantly.