Hemp From disordered lines for new staple fibre yarns and high-performance composite applications

The use of natural fibre-reinforced plastics for higher-stressed applications is currently often limited by the high price of high-quality semi-finished products. Therefore, the present study deals with developing yarns from cost-effective hemp from a disordered separation process (total fibre line) for composite reinforcements. Composites were fabricated using a miniature pultrusion process with thermosetting matrices from the yarns. The results show that around 90% of the flexural strength and flexural modulus of identically produced flax composites could be achieved with maximum values of 282 MPa for the flexural strength and 23.4 GPa for the flexural modulus. The yarns were additionally used to manufacture quasi-unidirectional fabrics to produce composite laminates using different manufacturing processes. The highest values were obtained for a laminate with 39 vol% fibre content, produced with a resin injection process in an autoclave, achieving a tensile strength of 155 MPa, Young's modulus of 19.4 GPa, a flexural strength of 174 MPa and bending modulus of 12.4 GPa. The characteristic values are sufficient to use the materials in applications with higher mechanical requirements.