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Dry vs. wet: Properties and performance of collagen films. Part II. Cyclic and time-dependent behaviours

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journal contribution
posted on 07.09.2020, 08:07 by Shirsha Bose, Simin LiSimin Li, Elisa MeleElisa Mele, Vadim SilberschmidtVadim Silberschmidt
Collagen constitutes one-third of human-body proteins, providing mechanical strength and structural stability. Films of collagen are widely used in tissue engineering as scaffolds for wound healing and corneal implants, among other applications, presupposing the investigation of their mechanical properties and performance under various loading and environmental conditions. Part I of this research (Bose et al., 2020) demonstrated a drastic change in the mechanical response of collagen films under in-aqua conditions when compared to dry specimens. It was also observed that collagen films exhibited a strain-rate-dependent hardening behaviour with a strain-rate-sensitivity exponent ranging from 0.02 to 0.2. In Part II, the cyclic and time-dependent behaviours of collagen films were analysed under different loading and environmental conditions. Strain ratchetting was observed for collagen subjected to cyclic loading under various stress levels and environmental (in-air and in-aqua) conditions, while the in-aqua samples demonstrated an increase in the stiffness (50% in the first cycle), which may be referred to as cyclic stiffening. In contrast, the dry samples showed a drop in the modulus after the first cycle, without any subsequent changes. Additionally, time-dependent viscoelastic properties were analysed, using dynamic mechanical analysis as well as creep and stress-relaxation techniques. Tan δ values for dry samples ranged from 0.05 to 0.075, while for hydrated ones it varied from 0.12 to 0.24. Collagen films exhibited primary and secondary creep stages, while the initial stress-relaxation was fast followed by a monotonous decay. The stress-strain-time data obtained from experiments were fitted in Prony series to estimate the relaxation moduli and times.

History

School

  • Mechanical, Electrical and Manufacturing Engineering
  • Aeronautical, Automotive, Chemical and Materials Engineering

Department

  • Materials

Published in

Journal of the Mechanical Behavior of Biomedical Materials

Volume

112

Publisher

Elsevier

Version

AM (Accepted Manuscript)

Rights holder

© Elsevier

Publisher statement

This paper was accepted for publication in the journal Journal of the Mechanical Behavior of Biomedical Materials and the definitive published version is available at https://doi.org/10.1016/j.jmbbm.2020.104040.

Acceptance date

12/08/2020

Publication date

2020-08-20

Copyright date

2020

ISSN

1751-6161

Language

en

Depositor

Prof Vadim Silberschmidt. Deposit date: 2 September 2020

Article number

104040