Material and mechanical behavior of bracket fungi context as a mechanically versatile structural layer

Bracket fungi sporocarps present promising environmentally friendly alternatives to harmful and wasteful structural applications with their high strength-to-weight ratio mechanical properties. Kingdom Fungi is estimated to have over three million species, yet only 4% of the species have been described by mycologists, and their mechanical behavior has been under-explored. This work aims to characterize the material behavior and mechanical properties of bracket fungi as a whole through micro-mechanical tensile testing combined with microstructural imaging and analysis of two representative species. The context layer from three distinctive fresh bracket sporocarps is used in this study. At the microstructure level, the bracket fungi have a preferred alignment in the hyphal network, which correlates to the radial direction. The bracket fungi exhibit an anisotropic mechanical behavior with higher ultimate tensile strength and elastic modulus in the radial direction, while the strain to failure is higher in the transverse direction. However, the bracket fungi exhibit an isotropic energy absorption, or toughness, behavior, with no statistically significant difference between the radial and transverse directions. The characterization of anisotropic mechanical properties and isotropic energy absorption will inspire the exploration of bracket fungi as a viable alternative to applications in various industries, such as aerospace and agriculture.