Effect of environmental relative humidity and damage on the tensile properties of flax and nettle fibers

The effects of environmental conditions and mechanical damage on the tensile stiffness and strength of two natural fibers, flax and nettle, are investigated. Flax and nettle both contain cellulosic fiber bundles in the outer layer of the plant, each bundle comprising many individual cells bonded together. Novel experimental equipment is designed and constructed to measure, under varying environmental conditions, the static and dynamic tensile moduli and the strength of individual fiber cells. As previous work has shown, the tensile modulus is dependent on environ mental relative humidity, but the effect of fiber damage is also significant. There is a correlation between the extent of damage, measured as the proportion of the fiber showing as bright under a polarizing microscope, and the modulus. When the effect of damage is taken into account, there is a consistent relationship between modulus and relative humidity.