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SUMMARY:Modeling of Fibrous Tissues Considering the Microstructure - Prof 
 Gerhard A. Holzapfel\, Graz University of Technology\, Institute of Biomec
 hanics\, Austria
DTSTART:20230217T140000Z
DTEND:20230217T150000Z
UID:TALK194020@talks.cam.ac.uk
CONTACT:Hilde Hambro
DESCRIPTION:Nowadays\, the 3D ultrastructure of a fibrous tissue can be re
 constructed in order to visualize the complex nanoscale arrangement of col
 lagen fibrils including neighboring proteoglycans even in the stretched lo
 aded state [1]. In particular\, experimental data of collagen fibers in hu
 man artery layers have shown that the fibers are not symmetrically dispers
 ed [2]. In addition\, it is known that collagen fibers are cross-linked an
 d the density of cross-links in arterial tissues has a stiffening effect o
 n the associated mechanical response.\nA first attempt to characterize thi
 s effect on the elastic response is presented and the influence of the cro
 ss-link density on the mechanical behavior in uniaxial tension is shown [3
 ]. A recently developed extension of the model that accounts for dispersed
  fibers connected by randomly distributed cross-links is outlined [4]. A s
 imple shear test focusing on the sign of the normal stress perpendicular t
 o the shear planes (Poynting effect) is analyzed. In [5] it was experiment
 ally observed that\, in contrast to rubber\, semi-flexible biopolymer gels
  show a tendency to approach the top and bottom faces under simple shear. 
 This so-called negative Poynting effect and its connection with the cross-
 links as well as the fiber and cross-link dispersion is also examined.\n\n
 References\n\n[1] A. Pukaluk et al.: An ultrastructural 3D reconstruction 
 method for observing the arrangement of collagen fibrils and proteoglycans
  in the human aortic wall under mechanical load. Acta Biomaterialia\, 141:
 300-314\, 2022.\n\n[2] G.A. Holzapfel et al.: Modelling non-symmetric coll
 agen fibre dispersion in arterial walls. Journal of the Royal Society Inte
 rface\, 12:20150188\, 2015.\n\n[3] G.A. Holzapfel and R.W. Ogden: An arter
 ial constitutive model accounting for collagen content and cross-linking. 
 Journal of the Mechanics and Physics of Solids\, 136:103682\, 2020.\n\n[4]
  S. Teichtmeister and G.A. Holzapfel: A constitutive model for fibrous tis
 sues with cross-linked collagen fibers including dispersion – with an an
 alysis of the Poynting effect. Journal of the Mechanics and Physics of Sol
 ids\, 164:104911\, 2022.\n\n[5] P.A. Janmey et al.: Negative normal stress
  in semiflexible biopolymer gels. Nature Materials\, 6:48–51\, 2007.\n
LOCATION:Department of Engineering - LR4
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