Bio-inspired composites: Using nature to tackle composite limitations

The high demand for engineering lightweight materials with an optimal strength- toughness balance is driving the research towards the design of innovative materials with great performance. Composites often provide the best solution for structural applications, offering a good combination of mechanical properties and low weight. However, the relatively low toughness of composite materials is often a limitation. Many researchers tried to overcome this limitation by mimicking nature principles, leading to a new class of composites with improved toughness: the biomimetic composites. Natural hierarchical materials are indeed a good source of inspiration for the design of new smart materials. Among these materials, bone is a promising candidate, showing a great combination of mechanical properties, and having a lightweight structure that provides support to a wide class of animal bodies. In particular, the remarkable toughness of bone makes it attractive for research studies. Here, we provide guidelines to design innovative materials, taking inspiration by the bone structure. The goal is to mimic the main toughening mechanisms occurring in bone microstructure, by implementing the key microstructural features of bone tissue in de novo composite materials. In this chapter, we show different case studies on the realization of new bone-inspired materials, by means of different manufacturing techniques, such as composite lamination and additive manufacturing. A complete characterization of the new materials shows how the bone-like pattern affects the crack path and the overall fracture behavior of the composites, leading to an improvement in the mechanical performance. Moreover, by observing the failure modes, it is possible to notice several similarities with the bone tissue. Microscopic analyses, indeed, confirmed that the toughening mechanisms were correctly implemented in the new materials and positively influenced the overall mechanical behavior.