Production and properties of a precision-cast bio-inspired composite

• Published in: Journal of materials science 2014, Vol.49 (1), p.43-51
• Main Authors: Fischer, Sebastian F., Thielen, Marc, Weiß, Philipp, Seidel, Robin, Speck, Thomas, Bührig-Polaczek, Andreas, Bünck, Matthias
• Format: Article
• Language: English
• Subjects: Aluminum base alloys; Characterization and Evaluation of Materials; Chemistry and Materials Science; Classical Mechanics; Composite materials; Composite structures; Crystallography and Scattering Methods; Dendritic structure; Ductile fracture; High strength; Materials Science; Molds; Polymer Sciences; Solid Mechanics; Struts; Tensile strength
• ISSN: 0022-2461; 1573-4803
• DOI: 10.1007/s10853-013-7878-4

The article presents the production and investigation of a bio-inspired metal–metal-composite inspired by the pomelo peel. The pomelo fruit is able to withstand a fall externally undamaged, even from heights of over 10 m most likely due to the hierarchical structuring of its foamy peel, which represents a complex composite structure. Especially the foam’s struts, which are cells from the biological point of view, consisting of liquid-filled cores and shells (cell walls) with relatively high strength, give point to a technical adaptation. With the objective to make use of the pomelo’s ability to absorb impact energy, the design of a pomelo strut is abstracted and transferred to aluminium/aluminium–silicon-alloy (A356) composite tensile specimens. Testing results show that the properties of the individual materials can successfully be combined. After fracture of the outer high strength, but less ductile A356-shell, the applied stress can still be absorbed by deformation of the inner highly ductile pure aluminium. As a result, the ductility of a bio-inspired composite is significantly higher compared with an A356 tensile specimen. By varying the mould and casting temperatures, the relationship between the production parameters and the quality of the composite is shown. A reduced mould and casting temperature lowers the dendrite arm spacing in the A356 outer shell of the composite material thus leading to an increased tensile strength. The detected metal bond between the two materials is mainly influenced by the interaction between the casting and the mould temperature.