Production and properties of a precision-cast bio-inspired composite
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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.
KeywordsMould Temperature Uniform Elongation Casting Temperature Metallic Bond Mould Filling
The authors would like to thank the RWP GmbH for their support during the simulation of the production process. Special thanks are extended to Dirk Freudenberg and his team for the realisation of the matrices, Jürgen Nominikat and Timm Ziehm for their support during the whole production process, Elke Schaberger-Zimmermann and Elke Breuer for the preparation of the metallographic sections, Michael Mathes for the SEM analyses and Franz Ernst for testing the tensile specimens. In addition to this, the authors gratefully acknowledge the financial support from the German Research Foundation (DFG) within the Priority Programme 1420.
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