title: New regime in the mechanical behavior of skin: strain-softening occurring before strain-hardening.
abstract: We report linear and non-linear shear tests on rat skin, evidencing a strain-softening regime, from 1% to 50% strain, followed by a strong strain-hardening regime, leading to a 'deck chair-shaped' stress-strain curve. The strain-softening regime was never reported as such in the literature, possibly mistaken for the linear regime in experiments starting above 1% deformation. The time-dependent response is akin to that of a gel, with a power-law frequency-dependent dynamic shear modulus ranging from ~5.6kPa to ~10kPa between 0.1Hz and 10Hz. We present an analytical non-linear viscoelastic model that accounts for both time-dependent and strain-dependent features of the skin. This eight-parameter model extends the one we proposed for parenchymatous organs by including strain-softening.
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, LBMC UMR_T9406, F69622 Lyon, France. Electronic address: stephane.nicolle@ifsttar.fr.
authors.forename: S
authors.initials: S
authors.lastname: Nicolle
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, CNRS, LBTI UMR 5305, F69367 Lyon, France.
authors.forename: J
authors.initials: J
authors.lastname: Decorps
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, CNRS, LBTI UMR 5305, F69367 Lyon, France.
authors.forename: B
authors.initials: B
authors.lastname: Fromy
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, CNRS, École Normale Supérieure de Lyon, UMR 5672, Laboratoire de Physique, F69364 Lyon, France.
authors.forename: J-F
authors.initials: JF
authors.lastname: Palierne
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004548:Elasticity; D051381:Rats; D012879:Skin Physiological Phenomena; D013314:Stress, Mechanical; D014783:Viscosity
keywords: Living tissues; Mechanical characterization; Nonlinear viscoelastic constitutive law; Shear