Probability distribution of fatigue strength of rotor blades (profar): Publishable final report EU joule III project JOR3-CT98-0266

In the period June 1997 ? July 2001 the EU funded project ?Probability Distribution of Fatigue Strength of Rotor Blades ? PROFAR? was carried out. The main objective of this project is to get a deeper understanding of the blade to blade variation of the fatigue strength of rotor blades and to determine the statistical distribution function by which this variation can be described.Furthermore the project aimed at the determination and quantification of the correlation between the measured fatigue strength of rotor blades and coupon data. To achieve the project objectives 37 small-scale blades have 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 real blades. In order to serve these purposes the 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, while the other aimed at failure in the geometrically complicated root section of the blade where 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 flapwise direction. The fatigue tests have been carried out at different stress levels. Besides fatigue, other failure modes like ultimate load are incorporated in the test sequence. The tests have been performed at three laboratories, the Stevin laboratory of the Technical University of Delft, The Netherlands; the test facilities of the Centre for Renewable Energy Sources, CRES in Pikermi, Greece; and a test facility at Ris?? National Laboratory, Roskilde, Denmark. The results of the blade tests have been correlated with coupon data for similar material obtained from coupon tests performed within this project and with corresponding material obtained from the existing data base FACT. Based on this correlation, test load factors were determined. The results of the tests show that: ? Although a serious attempt has been made to harmonise the tests within the different laboratories, the available equipment, the in house procedures and culture makes inevitable that differences in the tests occur between the different institutions. ? Ignoring the slight