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Title:
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Fatigue of stud joints for GFRP wind turbine blades [ECN-C--95-117]
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Author(s):
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Published by:
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Publication date:
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ECN
Energy Efficiency in Industry
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1995
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ECN report number:
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Document type:
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ECN-C--95-117
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ECN publication
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Number of pages:
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Full text:
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26
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Download PDF
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Abstract:
In order to allow a safe and economic design of wind turbines it is necessary to determine the high cycle fatigue properties of materials and
joints used in rotor blades. Constant amplitude fatigue tests were performed
with stud joint specimens from glass fibre reinforced polyester (GFRP),
produced under industrial conditions. In the selection tests several variants of the stud connection were investigated with static and some preliminary fatigue tests. The selection tests show that both stud construction concepts (Polymarin and Rotorline) have sufficient mechanical properties, static as well as with respect to fatigue behaviour. With the best performing type a fatigue investigation was started in order to obtain design data. The fatigue investigation of the final construction type shows that the slope of the tension-tension R=0.1 tests is approximately -1/9, which is close to the design concept of the studs. However, the slope -1/6 of the curve of the ompression-tension R=-1 tests is much steeper than expected. In the high cycle range there is no indication of a deflection of the linear log-log relation towards a possible fatigue limit. This means that the stud is probably very sensitive for through zero fatigue loads. In order to obtain a save and durable blade root construction these fatigue results must be carefully incorporated into the design process for the stud connection. The tests with moisture preconditioned specimens show that there is some but not a significant effect of moisture on the fatigue performance. 6 figs., 2 tabs., 6 refs.
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