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 t ensile stiffness and strength of two natural fibers, flax and nettle, are investigated. Flax and nettle both contain cellulosic fiber bundle s in the outer layer of the plant, each bundle comprising many individ ual cells bonded together. Novel experimental equipment is designed an d 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 o n environmental relative humidity, but the effect of fiber damage is a lso significant. There is a correlation between the extent of damage, measured as the proportion of the fiber showing as bright under a pola rizing microscope, and the modulus. When the effect of damage is taken into account, there is a consistent relationship between modulus and relative humidity.