The toughness of porcine skin: Quantitative measurements and microstructural characterization

Andrei Pissarenko; Wen Yang; Haocheng Quan; Boris Poyer; Alun Williams; Katherine A Brown; Marc A Meyers

doi:10.1016/j.jmbbm.2020.103848

The toughness of porcine skin: Quantitative measurements and microstructural characterization

J Mech Behav Biomed Mater. 2020 Sep:109:103848. doi: 10.1016/j.jmbbm.2020.103848. Epub 2020 May 15.

Authors

Andrei Pissarenko¹, Wen Yang², Haocheng Quan¹, Boris Poyer³, Alun Williams⁴, Katherine A Brown⁵, Marc A Meyers⁶

Affiliations

¹ University of California, San Diego, CA, USA.
² University of California, San Diego, CA, USA; Lawrence Berkeley National Laboratory, Berkeley, CA, USA.
³ École Normale Supérieure de Paris-Saclay, Cachan, France.
⁴ University of Cambridge, Cambridge, UK.
⁵ University of Cambridge, Cambridge, UK; University of Texas Austin, Austin, TX, USA.
⁶ University of California, San Diego, CA, USA. Electronic address: mameyers@ucsd.edu.

PMID: 32543412
DOI: 10.1016/j.jmbbm.2020.103848

Abstract

An exceptional tear resistance is required of the skin to protect the body from external attacks, environmental damage, and other forms of aggression. To estimate the toughness of juvenile porcine skin, we conduct two types of experiments on pre-notched specimens, placing the tissue under shear (Mode III) by using the classical trouser test with a 25 mm long pre-notch, and opening (Mode I) with an experimental setup with the same pre-notch length. We obtain two distinct average toughness values of J_IIIc≈20.4kJ/m² and J_Ic=30.4kJ/m², as a result of differences between these two modes of crack-tip loading and propagation, and collagen alignment. Digital image correlation coupled with single edge notch tests of 10 mm × 30 mm skin samples enables the mapping of the local strains around the tip of the crack. Effects of sample orientation and initial notch size ratio on the strain profile and on the net-section failure stress are discussed. The evaluation of the structure at the crack tip and regions undergoing more uniform states of deformation is conducted by ex situ transmission electron microscopy and in situ environmental scanning electron microscopy. Prior to crack propagation, the stress concentration is decreased by redistributing loads away from the crack tip, illustrated by gradual recruitment of collagen fibers ahead of the crack tip, thus delaying crack growth. After the crack has propagated, collagen fibers are substantially damaged, marked by delamination and recoil of the collagen fibrils.

Keywords: Collagen; Digital image correlation; Skin; Toughness; Transmission electron microscopy.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Microscopy, Electron, Scanning
Stress, Mechanical*
Swine