A Viscoelastic Analysis of the Keratin Composite: Part I: Longitudinal and Transverse Mechanical Properties

The static correspondence principle for viscoelastic composites has been applied to establish two viscoelastic fibrous composite models for keratin. The composite model comprising isotropic viscoelastic matrix and filament phases provides accurate pre dictions of the effective fiber mechanical properties ( longitudinal and transverse). The composite model successfully identifies the filament phase as the microfibril structure in the wool fiber. The mechanical properties of both constituent phases in the keratin fiber, the partially crystalline microfibrils and the amorphous matrix, are influenced by variations of the water content in the fiber. The longitudinal and transverse tensile and shear relaxation moduli are calculated for the keratin fiber at different moisture regain levels. The mechanical anisotropy of keratin is related to the constituent phase properties and the packing geometry of the composite.