Pummelos as Concept Generators for Biomimetically Inspired Low Weight Structures with Excellent Damping Properties

Abstract

Natural materials often exhibit excellent mechanical properties. An example of outstanding impact resistance is the pummelo fruit (Citrus maxima) which can drop from heights of 10 m and more without showing significant outer damage. Our data suggest that this impact resistance is due to the hierarchical organization of the fruit peel, called pericarp. The project presented in the current paper aims at transferring structural features from the pummelo pericarp to engineering materials, in our case metal foams, produced by the investment casting process. The transfer necessitates a detailed structural and mechanical analysis of the biological model on the one hand, and the identification and development of adequate materials and processes on the other hand. Based on this analysis, engineering composite foam structures are developed and processed which show enhanced damping and impact properties. The modified investment casting process and the model alloy Bi57Sn43 proved to be excellent candidates to make these bio‐inspired structures. Mechanical testing of both the natural and the engineering structures has to consider the necessity to evaluate the impact of the different hierarchical features. Therefore, specimens of largely varying sizes have to be tested and size effects cannot be ignored, especially as the engineering structures might be upscaled in comparison with the natural role model. All in all, the present results are very promising: the basis for a transfer of bio‐inspired structural hierarchical levels has been set.

Towards High‐Performance Bioinspired Composites

“…Biological materials are organized into hierarchical architectures exhibiting structural features that span over multiple length scales. Examples include materials as diverse as wood, bone, tendon, marine sponges, and fruits 112, 113. Recent research suggests that hierarchical structuring is a design strategy used in biological materials to significantly change their properties utilizing limited material choices and to enhance the material's overall mechanical properties by co‐operatively combining different functions that emerge from building blocks at each of the multiple length scales 27, 55, 114, 115…”

Plants as Model in Biomimetics and Biorobotics: New Perspectives

“…The principles have been exploited in the development of new materials for enhanced crash absorbers, based on metal foams (Fischer et al, 2010). …”

Cellulose‐Based Biotemplated Silica Structuring

“…[141] 6. [161][162][163] However, all of these structure types exist in nature [164,165] in an abundance of specific examples. silica, calcium carbonate or mixtures thereof.…”