The Mechanical Behavior of Wool Fiber in Water
1960 Volume 9 Issue 79 Pages 301-306
Details
1960 Volume 9 Issue 79 Pages 301-306
The mechanical behavior of wool fiber in water is studied by the free damped vibrational method at low frequency (period=4∼5sec) and large amplitude (maximum amplitude=2% extension) under various static strains and temperatures. In order to measure the stationary viscoelasticity, the logarithm of double amplitude must be decreased linearly with the vibration. In the case of wool in water, these straight lines (plots of logarithm of the double amplitudes (AN) against successive vibration numbers (N)) are concave or convex about the axis of the successive vibration number (N). There are three types of logAN∼N curves: Straight line and concave or convex against N-axis. The above three types are assumed as follows:
(1) Straight line:
The breaking and reformation of the secondary bonds are in equilibrium and a stationary state is attained.
(2) Convex curve:
The reformation of the secondary bonds exceeds the breaking during the vibration.
(3) Concave curve:
The breaking of the secondary bonds exceeds the reformation during the vibration.
The above hypothesis may explain the mechanical behavior of wool in water at various conditions. This is shown as follows:
1. The wool fiber is extended in the state where the breaking of the secondary bonds exceeds the reformation of the bonds, but during retraction the reformation exceeds. The change of the viscoelasticity under extension and retraction is reversible within 0∼30% extension region (Fig. 2∼3).
2. During the stress relaxtation at 10% extension, the breaking of the secondary bonds exceeds and a stationary state is attained with the elapse of time (Fig. 4).
3. When the vibration contains the yield point, the reformation of the bonds exceeds the breaking under large double amplitude, and the breaking exceeds the reformation under small double amplitude (Fig. 5).
4. Under rising temperature at 10% extension, the breaking of the bonds exceeds and under falling temperature, the formation of the bonds exceeds (Fig. 6).
The temperature dependency of the relative Young's modulus is compared with the data of Meredith and Feughelman. The temperature coefficient of Young's modulus at Hookean region derived by some workers are as follows:
