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UBC Theses and Dissertations

Mechanical response of reconstituted, freeze-dried collagen under compression loads Khosla, Amardeep Singh

Abstract

The mechanical response under uniaxial compression of collagen discs, made from freeze-dried collagen reconstituted at acid pH, was investigated at 22, 29.5, and 35°C (±0.3 C°). The pH during compression was maintained near the physiological level of 7.40-5. Connective tissues are known to be non-linear viscoelastic materials. It was felt, however, that the linearized, fluid transport-based model developed by Bert (1970) would adequately describe the behaviour of collagen "for small changes in hydration. [The model is linearized through the assumption that the diffusion coefficient, D(H), is a weak function of hydration, and is therefore constant for small changes in hydration]. The average diffusion coefficient, D(H), and the flow condictivity,k/n, were found to be stronger functions of hydration than expected in the hydration range investigated [1.9 to 5.5 g H₂O/g collagen], and this may have increased scatter in the results. Average values of D(H) and k/n at hydration 3.0 g H₂O/g collagen [i.e. skin hydration] were ~ 3.5x10⁻⁷cm²/s and ~ 6.0x10⁻¹¹cm⁴/dyne-s respectively. The compressive response of collagen was only weakly influenced by temperature, and possible thermal degradation of the molecules was indicated at 35°C. Some creep was also noted at times >5 t[sub ½], but no attempt was made to quantify it.

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