Influence of industrial processing parameters on the effective properties of long aligned European hemp fibres in composite materials

Hemp is a sustainable source of natural fibres that can contribute to meet the increasing demand for technical applications in the textile and the composite sectors. Continuous reinforcements can be produced using the existing flax machinery, initially developed for textile purposes. To achieve competitive and economically viable fibre yields and a fibre quality suitable for secondary processing and composite application, hemp needs to be adequately selected and prepared and the flax machinery and settings have to be adapted to the hemp specificities. In this context, this paper studies the influence of agronomic features and processing stages and settings on the effective tensile properties of fibres extracted from two hemp varieties determined using impregnated fibre bundle tests. Results show that the effective properties of fibres are maintained and even improved during processing, in particular during the hackling and stretching steps. Hemp can achieve properties comparable to high quality long flax fibres.