27—MECHANICAL PROPERTIES OF WOOL FIBRES II—SINGLE FIBRES AT 0% r.h. IN THE YIELD REGION

Some of the mechanical properties of the wool fibre are examined at 0% relative humidity. Young's modulus and stress relaxation over the strain range 1—20% are independent of temperature over the range 10—80°C. Young's modulus is also independent of the rate of straining over the range 0.75—250%/minute. In the stress relaxation experiments, the decay of stress is measured as a function of rate of straining R and is found to vary linearly with log R. The decay of stress also varies linearly with the initial load. In the creep experiments, the strain varies linearly with the logarithm of the time, and the shapes of the creep curves alter little with load and temperature. However, the creep amplitude varies with both load and temperature. It is suggested from a consideration of the experimental data that the mechanical behaviour of the fibre results from a distribution of forces acting upon extensible units of the Burte and Halsey type.