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In the course of biological evolution, plant stems have evolved mechanical properties and an internal structure that makes them resistant to various types of failure. The mechanisms involved during damage development and failure in bending are complex and incompletely understood. The work presented builds on a theoretical framework outlined by Ennos and van Casteren, who applied engineering mechanics theory to explain why different woody stems fail in different ways. Our work has extended this approach, applying it to a detailed analysis of one particular species: Fuchsia magellanica var. gracilis . When subjected to three-point bending, stems of this species exhibited one of two failure mechanisms: a plastic hinge or a greenstick fracture. We developed a predictive model using a computer simulation and a mathematical analysis using the theory of plastic bending. Required material properties were obtained from tests, the literature and imaging techniques. We found that greenstick fractures are more likely to occur in more lignified stems with a higher density. We discovered a new failure mode: an internal crack caused by tensile transverse stress. This work helps in understanding how plants have evolved their bending resistance and may assist in the creation of novel engineering structures inspired by these principles.

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Materials and structures for marine applications are often required to combine high mechanical performance with lightness, but traditional solutions are not always adequate to the scope. The application of biomimetic science could provide innovative and efficient solutions, whose research is the aim of the present paper. In the current work, bamboo samples were subjected to impact both on the outside and on the inside surface. It was found that the impact strength is correlated to the third power of thickness and that the softer inside layers may act as an energy absorbing structure, which enhance impact resistance. Impact tests were also performed on specimens whose outside surface had been abraded and on whole cylindrical sections. The role of graded and hierarchical structure in impact response, suggested some guidelines for bio-inspired structures design. Four bamboo-inspired structures were designed, based on the idea of combining corrugated panels with different geometrical characteristics to resemble bamboo graded and hierarchical structure. These structures were made using 3D printing and tested in compression. The best performance was obtained by the structure which more closely replicates bamboo's hierarchy. Structure performance could be predicted with reasonable accuracy using buckling theory.

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