From bio-sourced to bio-inspired cellular materials: A review on their mechanical behavior under dynamic loadings

Natural cellular materials can be used directly or as a constituent of bio-sourced composites for industrial applications involving dynamic loadings, usually for the purpose of absorbing mechanical energy. These biological materials can also be used as an inspiration to conceive more efficient heterogeneous structures for impact mitigation. In this review letter, we present two natural materials for which the properties have been studied dynamically: balsa wood and cork-based agglomerates. Both display an important strain-rate dependence but because of their different microstructure, this dependence is not the same. Consequently, a better understanding of the relationship between the hierarchical structure of natural cellular materials and their mechanical behavior, from quasi-static to dynamic, would be beneficial for the conception of new bio-inspired architected structures. We then focus on two types of bio-inspired architected structures: the functionally density graded cellular structures and the multi-layered architected structures. These two types of structures are gaining interest, but it appears that their dynamic behavior still lacks studying and understanding. More research linking the local strain mechanisms to their macroscopic mechanical behavior in quasi-static and dynamic would allow further architected structure optimization for mechanical energy absorption.