Crack-tip strain fields in collagen biomaterials for skin tissue engineering

The objective of this investigation was to determine the notch-tip strain fields in Type-I collagen biomaterials. Experiments were performed in-situ in a fixture mounted on the stage of an optical stereozoom microscope with edgenotched Type-I collagen tensile specimens. Image markers were added around the notch, and a tensile strain was applied. High-resolution images were collected at different levels of far-field strain. Image analysis was performed to measure the displacements of individual surface markers. The resultant displacement fields were analyzed to yield in-plane surface strain profiles along trajectories perpendicular to the crack plane. The results revealed significant local strain amplifications near the notch tip of nearly twenty times. These results are discussed in light of existing constitutive models for crack-tip strain fields.