Some Mechanical Properties of Wool Fibers in the "Hookean" Region from Zero to 100% Relative Humidity

Abstract

At 20°C and for all moisture contents, the mechanical behavior of wool fibers up to 1% extension in the Hookean region is linear viscoelastic. The equilibrium Young's modulus, based on the wet cross-sectional area of the wool fiber, is inde pendent of moisture content and is equal to 1.4X 1010 dynes-cm2. The dynamic or transient behavior of a fiber at any moisture content at 20°C can be replaced by a spring contributing a fixed stiffness of 1.4X 1010 dynes/cm2 to the dynamic Young's modulus together with a viscous dashpot in parallel and having moisture-dependent characteristics. The action of water, which in the original two-phase matrix-microfibril model, was proposed to weaken the matrix, must now be con sidered to increase the segmental mobility of the molecular structure of the matrix. Further, mechanical equilibrium between matrix and microfibril is taken to exist for the wet wool fiber, rather than the dry fiber.