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Generalized limit surfaces - with an example of hard foams

 
: Fahlbusch, Nina-Carolin; Becker, Wilfried; Kolupaev, Vladimir

:

Naumenko, K.:
Advanced Methods of Continuum Mechanics for Materials and Structures
Singapore: Springer Science+Business Media, 2016 (Advanced structured materials 60)
ISBN: 978-981-10-0958-7 (Print)
ISBN: 978-981-10-0959-4 (Online)
pp.337-365
English
Book Article
Fraunhofer LBF ()
Limit Surface; hard foam

Abstract
Hard foams are often used in aircraft, submarine, and automotive industry structures mostly as core in sandwich structures. The design of the critical components made from hard foams requires the knowledge of their material behaviour. Nowadays, this knowledge is gained from tests on specimens under tension, compression, torsion, and hydrostatic compression. Further tests are needed to describe the material behaviour under multi-axial loading reliably, but with default testing technology this is difficult to realize. Missing data can be predicted by numerical simulations of the microstructure. The calculated points of failure are needed to be approximated by a limit surface for the dimensioning and optimizing of engineering applications. The most known generalized strength hypotheses, however, restrict the shape of the surfaces in the principal stress space. In general, they are not suitable to describe the material behaviour of hard foams appropriately. The Capurso–Haythornthwaite generalization is chosen for the current application. It enables the description of limit surfaces with a large number of different shapes in the π-plane as well as varying shapes in the π-plane along the hydrostatic axis. The criterion takes into account the hydrostatic tensile and compressive stresses. The curvature of the meridians can be adjusted. In the current approach, a general fitting procedure is developed for the determination of the parameters of the criterion. The proposed method is not limited to polymer foams. The application to other materials like aerated concrete, cellular ceramics, and metal ceramics is possible.

: http://publica.fraunhofer.de/documents/N-423088.html