Mater.Sci.Technol. 16, 935-939, 2000
T. Daxner, F.G. Rammerstorfer and H.J. Böhm
Institute of Lightweight Structures and Aerospace Engineering, TU Wien, Vienna, Austria
Metallic foams show some potential for being produced with controlled
spatial variations in their density.
This suggests employing them as graded materials in space filling lightweight
structures in analogy to cortical bone, a natural cellular material, that
displays increased density in regions of high loading.
In the present study the influence of the mechanical properties of aluminium
foams on the results of an optimisation of the foam density distribution with
regard to structural strength and stiffness was examined.
Regression formulae for the relationships between stiffness and strength
of metallic foams on the one hand and effective density on the other hand
can be fitted to the results of uniaxial compression tests of a certain
brand of metallic foam.
The results and additional assumptions such as overall isotropy and a yield
surface suitable for cellular materials can be implemented into a finite
element program adapted for performing stiffness optimisation on the basis
of a density adaptation similar to the remodelling of bone.
Some applications are presented that show how foams with gradients in the
apparent density may be employed to obtain optimal structural behavior for
classical design problems.