Bone-Inspired Composites—A Path Towards Multifunctionality

Toughness, stiffness, and strength are major characteristics of biological hierarchical composites, and their combination is a long-sought objective for engineering design. Nature achieves the balance of such properties through a combination of multiscale key features. Yet, emulating all these features and achieving multifunctionality into synthetic de novo materials is rather challenging. Here, we fine-tune manual lamination, to implement a newly designed bone-inspired structure into fiber-reinforced composites, also providing repairing ability. We draw inspiration from the microstructure of cortical bone and we implement the characteristic features (i.e., osteons, Haversian canals, and lamellae) into a fiber-reinforced composite at a larger scale. We adopt a comprehensive approach, which includes design via numerical simulations, ad hoc manufacturing techniques, and experimental testing to achieve a novel composite design with an optimal tradeoff of fracture toughness, stiffness, strength, and lightweight.<br/>The proposed solution represents an optimal lightweight material with better performance than conventional materials, such as metals and alloys, and additional functionalities. The results also show how the new design significantly boosts the multifunctionality compared to a classic laminated composite, made of the same building blocks, also offering an optimal tradeoff with stiffness and strength. The major observed fracture mechanism is the continuous deviation of the crack from a straight path, promoting large energy dissipation and preventing a catastrophic failure. The hollow canals, inspired by the bone Haversian c., besides contributing to a further weight reduction, also provide a route to add self-healing capability. The new insights resulting from this study can guide the design of de novo fiber-reinforced composites toward better mechanical performance and multiple functionalities with the final goal of consolidating multiple parts and functions into a single one, reaching the level of synergy and multifunctionality of their natural counterparts.