In situ tensile testing of human aortas by time-resolved small-angle X-ray scattering.

The collagen diffraction patterns of human aortas under uniaxial tensile test conditions have been investigated by synchrotron small-angle X-ray scattering. Using a recently designed tensile testing device the orientation and d-spacing of the collagen fibers in the adventitial layer have been measured in situ with the macroscopic force and sample stretching under physiological conditions. The results show a direct relation between the orientation and extension of the collagen fibers on the nanoscopic level and the macroscopic stress and strain. This is attributed first to a straightening, second to a reorientation of the collagen fibers, and third to an uptake of the increasing loads by the collagen fibers.