A full, deep sound tells him that the laminate is homogeneous, while a more flat, hollow tone indicates irregularities in the material.
This is a thermographic image of air inclusions (light-colored) in a rotor blade. Credit: Fraunhofer WKI
Delaminated and hollow sections of a certain size near the surface can also be detected by running an expert hand over the surface material. But even an experienced inspector cannot find all hidden faults in this way.
Rotor blades consist mainly of glass fibers which are processed to form mats or meshes. In order to make a 60-meter rotor blade, hundreds of these mats have to be laid flat inside a mold and impregnated with special resins in a vacuum.
Even minor irregularities can cause air bubbles or other faults to form, and these often lead to mechanical stresses in the material when the blade is subjected to everyday loads. As a consequence, the laminate can rip and cause the rotor blades to fail prematurely.
Researchers at the Fraunhofer Wilhelm-Klauditz-Institut WKI in Braunschweig are able to make such faults visible. "Infrared thermography is well suited to this task, as it is fast, relatively cheap and doesn't cause any damage," explains WKI project manager Dr. Hiltrud Brocke. "The surface is briefly heated with an infrared radiator. A special camera shows how the heat front spreads inside the material. If the front hits on any air inclusions or delaminated areas, it accumulates because heat spreads less in air than in solid laminate."
In this way, the researchers can peer several centimeters into the material. "Because the equipment – the infrared radiator, a camera and a computer – is mobile, we can carry out measurements during production, at the end of the transport route, and also on fully assembled wind energy plants," says Brocke. The researchers will be demonstrating their technology on a rotor blade section incorporating several typical faults at the Hannover-Messe from April 20 to 24 (Hall 27, Stand G20).
Hiltrud Brocke | EurekAlert!
Electromagnetic water cloak eliminates drag and wake
12.12.2017 | Duke University
Two holograms in one surface
12.12.2017 | California Institute of Technology
MPQ scientists achieve long storage times for photonic quantum bits which break the lower bound for direct teleportation in a global quantum network.
Concerning the development of quantum memories for the realization of global quantum networks, scientists of the Quantum Dynamics Division led by Professor...
Researchers have developed a water cloaking concept based on electromagnetic forces that could eliminate an object's wake, greatly reducing its drag while...
Tiny pores at a cell's entryway act as miniature bouncers, letting in some electrically charged atoms--ions--but blocking others. Operating as exquisitely sensitive filters, these "ion channels" play a critical role in biological functions such as muscle contraction and the firing of brain cells.
To rapidly transport the right ions through the cell membrane, the tiny channels rely on a complex interplay between the ions and surrounding molecules,...
The miniaturization of the current technology of storage media is hindered by fundamental limits of quantum mechanics. A new approach consists in using so-called spin-crossover molecules as the smallest possible storage unit. Similar to normal hard drives, these special molecules can save information via their magnetic state. A research team from Kiel University has now managed to successfully place a new class of spin-crossover molecules onto a surface and to improve the molecule’s storage capacity. The storage density of conventional hard drives could therefore theoretically be increased by more than one hundred fold. The study has been published in the scientific journal Nano Letters.
Over the past few years, the building blocks of storage media have gotten ever smaller. But further miniaturization of the current technology is hindered by...
With innovative experiments, researchers at the Helmholtz-Zentrums Geesthacht and the Technical University Hamburg unravel why tiny metallic structures are extremely strong
Light-weight and simultaneously strong – porous metallic nanomaterials promise interesting applications as, for instance, for future aeroplanes with enhanced...
11.12.2017 | Event News
08.12.2017 | Event News
07.12.2017 | Event News
14.12.2017 | Health and Medicine
14.12.2017 | Physics and Astronomy
14.12.2017 | Life Sciences