Influence of Geometry and Tissue Damage on the Mechanical Behaviour of Skin Meshing

Abstract

Skin meshing increases graft coverage, yet the clinically achieved expansion often falls below the manufacturer's nominal meshing ratio. Previous elastic analyses have demonstrated that mesh topology and skin anisotropy strongly influence graft expansion; however, the effect of progressive damage at larger deformation remains unexplored. This study therefore investigates how progressive damage affects the expansion and mechanical response of skin meshes. The performance of auxetic mesh geometries is compared with conventional Zimmer mesher (ZM) geometry. Human back skin was modelled using a one-term Ogden ground matrix and a Gasser Ogden Holzapfel (GOH) collagen network, with separate scalar Kachanov-type continuum damage variables for each constituent. The auxetic geometries, including 1st- and 2nd-order alternative slits (AS1 and AS2), I-shaped (IS) and H-shaped (HS) re-entrant patterns, and ZM, were analysed with Langer's lines oriented either parallel or perpendicular to the loading direction. Hyperelastic and damage-based formulations were compared up to 25% strain, and the damage-based simulations were subsequently extended to 40% strain. ZM was further loaded to 155% strain; the area ratios attained by HS at 40% strain were matched by ZM at 142.1% and 124.7% strain for Langer's lines parallel and perpendicular to loading, respectively. Results indicate that HS achieves greater coverage than ZM for a given stretch, whereas its damage advantage depends on the orientation of Langer's lines.