Mechanical Behaviour in the Wet and Dry Stage of Romanian Yarns Made from Flax and Hemp

Flax and hemp yarns will constantly be used in the clothing field and in different technical applications. Deformation during stretching in the dry and wet states of flax and hemp yarns obtained from boiled or bleached roving was studied. Structure modifications of the yarn and fibre components as a result of tension were highlighted by load-extension curve analysis. The following specific characteristic quantities were measured and calculated on the diagrams: the limit of proportionality, the tensile yield stress, the breaking limit, the mechanical breaking work, and the mechanical work factor. The study of these data established maximum values of the processing tension that dry and wet flax and hemp yarns could stand without breaking. Moreover, analysis of the mechanical work factor enabled the estimation of the strain capacity of the yarns studied and their ability to support a tension impact load. The load and displacement at which the first breaking destruction phenomena of the yarn fibres appear are those corresponding to the tensile yield stress. Thus, it is possible to establish the maximum tensions that the yarn could support during processing without fibres breaking. An original evaluation of the tensile properties of flax and hemp yarns was developed.