Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bonded rotor blade joints: Improved test method reduces scale-up risks

25.02.2011
After a five year term, the EU funded UpWind research project is now drawing to a close. One aim of this project was to develop a more comprehensive test for bond lines used in the manufacturing process for rotor blades.

Prior to the production of prototypes, adhesive tests have hitherto only been undertaken on coupon specimens. Researchers at Fraunhofer IWES, together with industrial partners, have now developed a subcomponent test as an intermediate step. This provides additional understanding of material behavior on a structure-relevant scale. This more comprehensive approach reduces uncertainty for scale-up process to subcomponent design stage.

The aim of the UpWind project was to develop accurate, verified tools and component concepts for very large wind turbines (8-10 MW), both onshore and offshore. Ever longer rotor blades are being used for multi-megawatt wind turbines. They usually consist of two half-shells, which are bonded together with special adhesive. The loads that act on the bonded joint and the requirement for a service life of 20 years put extreme demands on the bond line. The latter can have a thickness of about 10 millimeters and a length of about 60 meters.

More realistic load distribution
Up until now ca. 15 centimeter long coupon specimens were certified prior to the prototype stage. However, due to production and geometry effects, the load distribution on these specimens differed considerably from the actual load distribution on the rotor blade prototypes.
As part of the EU funded UpWind project, scientists from the Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) investigated whether a so-called beam test can meet these requirements. These activities were

enhanced by parallel industry projects done with Henkel. A “beam in bending” test methodology that was has been developed in collaboration with Henkel was the starting point of the improvement.

“Knowledge of the physical properties of our products under in-service conditions is essential for successful applications,” explains Felix Kleiner, Manager of Adhesive Engineering at Henkel AG & Co. KGaA. “The new test method allows economic evaluation of different adhesives and design variations”. The base model that was used for this was an I-beam - a model which takes into account two bonded seams between spar cap - shear web - spar cap.

Enhanced understanding of material behavior
These tests provided information about the mechanisms of material fatigue and material failure. “In order to investigate the mechanical behavior of the adhesive in a relatively large adhesive volume, the beams were designed to have a critical section”, says Florian Sayer, Team Leader of "Component and Material Testing" at Fraunhofer IWES. This enhanced understanding of material behavior is being utilized in a follow-up research project to scrutinise further options for bond line structuring that will be summed up in a detailed catalogue. Moreover, a simplified numerical beam model for simulating material fatigue at the bonded seam will be developed. The beam test method that was validated in the project is available for interested industrial parties.

Uwe Krengel | Fraunhofer-Institut
Further information:
http://www.upwind.eu
http://www.iwes.fraunhofer.de

More articles from Materials Sciences:

nachricht Getting closer to porous, light-responsive materials
26.07.2017 | Kyoto University

nachricht Multitasking monolayers
25.07.2017 | Vanderbilt University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

 
Latest News

CCNY physicists master unexplored electron property

26.07.2017 | Physics and Astronomy

Molecular microscopy illuminates molecular motor motion

26.07.2017 | Life Sciences

Large-Mouthed Fish Was Top Predator After Mass Extinction

26.07.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>