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 Mat4Rail: EU Research Project on the Railway of the Future
23.02.2018 | Universität Bremen

nachricht Atomic structure of ultrasound material not what anyone expected
21.02.2018 | North Carolina State 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: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>