Community Research and Development Information Service - CORDIS

Established knowledge of the blade to blade variation of the fatigue strength of rotor blades

Fatigue strength of rotor blades shows variations, amongst other things due to the inherent scatter of material properties and the inevitable scatter in the production of blades. To account for this uncertainty, a safety factor is prescribed in design codes. Likewise an additional test load factor has to be applied in full scale blade testing. To determine these factors in a rational manner, a deeper understanding of the variation in the fatigue strength of rotor blades is required. In order to gain this knowledge a large number of small blades has been tested both static and in fatigue.

Next to these blades a number of coupons of identical material as that of the blades has been tested statically and under fatigue loading.

The tests served two main purposes, finding the scatter in the blade properties and relating the coupon test data to actual failure of the real blade. In order to serve these purposes two different sets of test were done. One set aimed at failure in the prismatic outboard section of the blade in the parent glass fibre material, and one set aimed at failure in the geometrically complicated root section of the blade were failure of the bonding line, collapse of the spar or other mechanisms can be observed. These latter tests were done both in edgewise and in flap wise direction.

Reports describing the results of the tests and the evaluation of the results are available.

The test results and the results of the evaluation of the test results are described in detail in reports, in which the following subjects are considered:
- Results of the blade tests (static and fatigue);

- Results of the coupon tests (static and fatigue);

- Evaluation of the test results;

- Correlation of blade tests with coupon tests;

- Conclusions about applicability of results.

Reported by

Energy research Centre of the Netherlands (ECN)
Westerduinweg 3
1755 ZG Petten
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