Structural properties of laminated Douglas fir/epoxy composite material

This publication contains a compilation of static and fatigue strength data for laminated-wood material made from Douglas fir and epoxy. Results of tests conducted by several organizations are correlated to provide insight into the effects of variables such as moisture, size, lamina-to-lamina joint design, wood veneer grade, and the ratio of cyclic stress to steady stress during fatigue testing. These test data were originally obtained during development of wood rotor blades for large-scale wind turbines of the horizontal-axis (propeller) configuration. Most of the strength property data in this compilation are not found in the published literature. Test sections ranged from round cylinders 2.25 in. in diameter to rectangular slabs 6 by 24 in. in cross section and approximately 30 ft. long. All specimens were made from Douglas fir veneers 0.10 in. thick, bonded together with the WEST epoxy system developed for fabrication and repair of wood boats. Loading was usually parallel to the grain. Size effects (reduction in strength with increase in test volume) are observed in some of the test data, and a simple mathematical model is presented that includes the probability of failure. General characteristics of the wood/epoxy laminate are discussed, including features that make it useful for a wide variety of applications

D.: ‘Scaling of composite Wind Turbine Blades for Rotors of 80 to 120 meter Diameter

Background This work was completed as part of the U.S. Department of Energy's WindPACT Program. The purpose of the WindPACT Program is to explore the most advanced technologies available for improving wind turbine reliability and decreasing cost of energy. In the initial phase of the WindPACT Program, scaling studies ͓1͔ were performed to investigate the scaling of current commercial turbine designs to the multi-megawatt size range, to identify size limits for critical components and technologies, and to provide input for follow-up studies under the program. The Blade System Design Study ͑coordinated by Sandia National Laboratories͒ concerns alternative materials, structural designs, and manufacturing technologies for potential application to multi-megawatt turbine blades. Under the Turbine Rotor Design Study ͑coordi-nated by the National Renewable Energy Laboratory͒, aeroelastic simulations and component cost models are being used to evaluate incremental changes in system cost of energy ͑COE͒ resulting from alternative blade materials, blade structural designs, rotor configurations, and turbine control strategies ͓2͔