The critical role of corrugated lamellae morphology on the tough mechanical performance of natural Syncerus caffer horn sheath

Horns from the Bovidae family represent extremely tough natural composites that resist flexural and impact damage during combat. However, the microstructure characteristics of these horns' sheaths and how this affects their mechanical properties remain to be explored. In this work, we report that the Syncerus caffer horn sheath exhibits the highest tensile strength of 183 MPa and fracture energy of 36.8 MJ m-3, superior to other reported bulk natural materials. Comprehensive structure characterizations pin down the key factors of the horn sheath as the corrugated lamellae morphology. Finite-element modeling verifies that the critical characteristics of curved corrugated lamellae have a profound effect on the flexural and impact behavior. Furthermore, the ridge region for the highly curved lamellar morphology corresponds to greater disulfide cross linking with X2.6% sulfur, suggesting a purposeful evolution of the heterogeneous composition. This work aims to provide insights into the bio-inspired design of superior structural materials.