Abstract
We report on the structure and mechanical properties of horns from a desert big horn sheep, Ovis canadensis. Horns must be strong and durable as they are subjected to extreme loading impacts, making them superior, impact resistant structural material. Horns are composed mainly of α-keratin, a fibrous, structural protein found in hair, nails, claws and hooves. The horn is a lamellar structure of keratin sheets (20-40 micrometers thick) enclosing tubes (about 90 micrometers in diameter) running in the longitudinal (growth) direction. The purpose of this work was to correlate the structure and the impact resistance properties, such as energy absorption and work of fracture, and to determine failure mechanisms. Hardness tests were conducted in longitudinal, transverse, and radial directions and samples were tested in bending and compression to failure in both wet and dry states. The fracture surfaces were examined by optical and scanning electron microscopy (SEM). Correlation of mechanical properties with the orientation will be discussed along with fracture mechanism. This research is supported by the National Science Foundation grant DMR 0510138.