Collagen orientation and leather strength for selected mammals.

Collagen is the main structural component of leather, skin, and some other applications such as medical scaffolds. All of these materials have a mechanical function, so the manner in which collagen provides them with their strength is of fundamental importance and was investigated here. This study shows that the tear strength of leather across seven species of mammals depends on the degree to which collagen fibrils are aligned in the plane of the tissue. Tear-resistant material has the fibrils contained within parallel planes with little crossover between the top and bottom surfaces. The fibril orientation is observed using small-angle X-ray scattering in leather, produced from skin, with tear strengths (normalized for thickness) of 20-110 N/mm. The orientation index, 0.420-0.633, is linearly related to tear strength such that greater alignment within the plane of the tissue results in stronger material. The statistical confidence and diversity of animals suggest that this is a fundamental determinant of strength in tissue. This insight is valuable in understanding the performance of leather and skin in biological and industrial applications.