The results of the project have Johnny Jakobsen published in a number of scientific articles, inclu

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PhD student bubble wrap kids Johnny Jakobsen has developed a "crack stops" that can intercept and stop cracks developing sandwich constructions in, among other ships and turbine blades. By Eskil Sorensen April 13, 2008 at. 10:00
It goes fast when cracks in sandwich structures develop into actual fracture, and it can be disastrous bubble wrap kids for the wind turbine blade, ship or airframe, where you have a hard composite material on both outer sides and a foam material in the middle.
Johnny Jakobsen's supervisor at the beginning bubble wrap kids of the project, Associate Professor Elena Bozhevolnaya, discovered bubble wrap kids that under certain circumstances could deflect revnes ran through the core material in a sandwich construction. This put the two on the trail of a solution to the sudden rupture.
Sandwich without peel-stops: The crack of the sandwich structure runs in the core material along the outer fiber material. Without crack stops continues crack and split it apart. Cracks may be controlled
Cracks in a sandwich construction will often run into the foam material along with the hard outer layer. Such a cracking called delamination in the jargon. The hike along the outer material is dangerous. It usually leads to the whole structure collapses.
Elena Bozhevolnaya and Johnny Jakobsen discovered that if you placed a second material as a wedge at an acute angle, so you could get the crack to hike up the material bubble wrap kids and not continue along the outer material. Crack Stops polyurethane
To find the right solution implemented Johnny Jakobsen a series of experiments with different types of wedge-shaped chocks in different materials. He has, among other constructed crack stoppers of aluminum.
After the success in getting the crack to leave the outer material was a disappointment. bubble wrap kids The crack had a tendency to look back toward the outer material again. The solution was to use it very tough material polyurethane. It allowed simply do not crack to get inside. Theoretical model
"We bubble wrap kids built a finite element model of the sandwich structure. Here we could put various small injuries into the material and using theories predict how a crack would develop. It has been exciting all the time to work alternately with experiments and theory. I have been able to go into the laboratory and determine if what I had intended me to even fit in practice. Conversely, experiments bubble wrap kids inspired to develop the theory, "says bubble wrap kids the 30-year-old engineer and soon Ph.D.
As he worked his way up to a crack stops, which worked in practice. Crack stopper is shaped like a hand holding on an apple. The "fingers" of the hand is located bubble wrap kids along the outer layers. They pick up the cracks and sends them towards the center, where they stopped.
Benefits of crack stopper is that an incipient damage is not progressing quickly and violently, and that the sandwich structure does not lose all its static strength, explains Johnny Jakobsen, who also had ole Thybo Thomsen and Associate Professor Jens H. Andreasen as supervisors bubble wrap kids on the project. And along the way Johnny Jakobsen had a four-month stay at Florida Atlantic University, where one of the world's prominent composite scientists, Leif Carlsson, professor. Patent bubble wrap kids Application
The results of the project have Johnny Jakobsen published in a number of scientific articles, including the prestigious journal Composite Science and Technology, bubble wrap kids and Aalborg University has filed a patent application for the technology.
"I think the greatest potential in the shipping bubble wrap kids industry for example for large hulls of yachts or ships which must withstand loads. It can also be places where must be fixed to something, for example a motor, which also has great stresses on the material, "he says.
Crack stopper will not only be used in beam-like bubble wrap kids structures, but to surfaces. Here, one might place the crack stopper in a pattern such that any cracks are prevented from spreading. They will so to speak be enclosed in a square.
PhD projects gives companies a technological boost and promises thus competitiveness. During 2008 we will engineer production present some of the best PhD projects. We focus on projects with direct relevance to Danish industry.
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