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ECN publication
The effect of moisture on the fatigue performance of glass fibre reinforcedpolyester coupons and bolted joints
Published by: Publication date:
ECN ECN 1996
ECN report number: Document type:
ECN-C--96-015 ECN publication
Number of pages: Full text:
34 Download PDF  

Although generally glass fibre reinforced plastics (GFRP) are found tohave good weathering properties, the effects of moisture on the fatigue properties are not negligible. In order to investigate the influence of moisture, fatigue tests were performed on preconditioned GFRP coupons and bolted joints. The results are compared to dry GFRP coupons and bolted joints from a previous fatigue study. The investigation on the preconditioned coupons shows that testing in a wet environment reduces the lifetime significantly. Testing under wet and hot conditions even reduces the lifetime by about 2 decades. However, after testing in the dry lab environment there is hardly any difference in fatigue lifetime between the normal and preconditioned specimens. Neither variants of the ENWISPER preconditioned coupon tests showed a degradation in lifetime compared to the reference set. For the bolted joints, there is only a small reduction in lifetime caused by the ENWISPER preconditioning. From the results it can be concluded that moisture significantly affects the fatigue lifetime during testing and that the influence of preconditioning is negligible. The combination of moisture and fatigue loading can be a critical condition for a wind turbine blade, especially on locations where the GFRP is not coated. Therefore an increased fatigue damage by more than one order of magnitude can be expected during the time moisture is condensed inside the blade. 7 figs., 8 tabs., 13 refs.

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