Structure and Properties of Bovine Hoof Horn

Abstract

Fracture behaviour and bending stiffness of bovine hoof horn has been explored at a variety of hydration levels and in different orientations. The failure paths avoid fibre/tubule breakage where possible and hence preferred direction for cracks is along the direction of the intermediate filaments and in the direction of the tubules. The stiffness of bovine hoof horn becomes lower with increasing moisture content as would be expected and it is found that the difference is much greater than the influence of sample orientation. By measuring the stiffness at increasing water content it has been possible to display the whole range of properties from ductile to rather more brittle behaviour when very dry. The behaviour does not change until well below the natural water content of the fresh leaving a large margin of safety. The tests on bending samples within the plane of the outer wall, perpendicular to the tubules, did not show significant difference in stiffness values compared with tests parallel to the tubules, neither dry nor fully hydrated. It is concluded that the primary function of the intermediate filaments is to direct the cracks and provide fracture resistance, rather than changes in stiffness. However, further work is needed to establish the full structure/property relationships within this fascinating three-dimensional composite material so that we might learn how to incorporate some of its lessons into our composite structures.