The Elastic Anisotropy of Keratinous Solids I. The Dilatational Elastic Constants

The elastic anisotropy of four forms of a-keratin, ram's horn, rhinoceros horn, baleen (whalebone), and the cortex of African porcupine quill, has been studied by measurement of the velocity of propagation of dilatational elastic waves of 5 Mc/s frequency along the principal axes, by the total reflection method. It has been found that ram's horn is transversely isotropic about the radial direction and that rhinoceros horn is approximately transversely isotropic about the fibre direction. This is directly correlated with the histological structure of these materials, which here predominates over the molecular structure in determining the nature of the elastic anisotropy.