The Critical Role of Corrugated Lamellae Morphology on the Tough Mechanical Performance of Natural <i>Syncerus caffer</i> Horn Sheath

Horns of Bovidae family represent extremely tough natural composites that resist flexural and impact damage during combats. However, the microstructure characteristics of the outer sheath of these horns and how this affects their mechanical properties and resistance to damage remain to be explored for the Bovinae subfamily. In this work we report that the Syncerus caffer horn sheath exhibits the highest toughness among the bovine horn sheaths. Its mechanical properties are closely related to its corrugated lamellae morphology. Finite element modeling verifies that the critical design characteristics of the curved corrugated lamellae with inter-lamellar connections has a profound effect on the flexural and impact mechanical behaviour of the sheath. Furthermore, the stress concentration at the ridge region for the highly curved-lamellar morphology is proved to possess rich disulphide crosslinking, suggesting a purposeful evolution of the heterogeneous lamellae structure. This work aims to provide insights into the toughening mechanisms of natural horn sheaths, and to encourage biomimetic design of superior structural materials.