Improved stud configurations for attaching laminated wood wind turbine blades
In order to improve joint strength for bonded studs in laminated wood structures (wind turbine blades) a series of designs was developed and tested. Each design systematically varied a parameter which was expected to have a significant effect on performance. The structural capability of each design was established based on tension-tension fatigue tests, and it was found that a stud with a concave tapered carrot design, bonded in place with an epoxy thickened with chopped carbon fiber, was the most effective design. Further improvements in joint performance could be made by augmenting the laminated wood with thin plies of carbon cloth (10 percent thickness buildup) in the area of the stud. Two designs were selected for further testing, which demonstrated that joint strengths approaching the membrane wood strength could be achieved. For a 3- by 3-inch wood block, an ultimate load exceeding 100,000 lbs could be introduced through a single bonded stud. For the same type of specimen in cyclic tension at an R-ratio of 0.1, the bonded studs were projected to have a fatigue life of 4 x 10/sup 8/ cycles at maximum loads of 30,000 lbs. For reversed axial fatigue, a reduction of 25 percent from these numbers was shown to be appropriate. These values represent an improvement of 100 percent over the stud designs used previously for laminated wood wind turbine blades. However, temperatures of 100/sup 0/F with humidity at 100 percent in certain cases caused a loss of ultimate load capability approaching 35 percent and a loss of fatigue capacity approaching 50 percent. While this result may have been specimen-related, additional testing or a change in the epoxy resin system should be considered before using the bonded stud designs in hot, humid environments.
- Research Organization:
- National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
- DOE Contract Number:
- AI01-76ET20320
- OSTI ID:
- 5154057
- Report Number(s):
- DOE/NASA/20320-66; NASA-TM-87109; ON: DE86001613
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
170602* -- Wind Energy Engineering-- Turbine Design & Operation
COMPRESSION
DESIGN
EPOXIDES
FASTENERS
FATIGUE
JOINTS
MACHINERY
MECHANICAL PROPERTIES
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
POLYMERS
RESINS
TENSILE PROPERTIES
TURBINE BLADES
TURBINES
TURBOMACHINERY
WIND TURBINES
WOOD