Systematic investigation of the critical fibre length of carbon fibre nonwoven composites

The present study investigates the direct influence of fibre length on the mechanical properties of nonwoven-reinforced carbon composites. For this purpose, carbon fibres of defined finite fibre length are processed in combination with thermoplastic fibres to form hybrid nonwovens with isotropic fibre orientation. These are consolidated to sheet material and are comprehensively mechanically characterised subsequently. In addition, a comparison is made with a theoretical critical fibre length determined by means of single-fibre measurement. The results quantifiably suggest for the first time that within a fibre length range relevant for the nonwoven processing of technical staple fibres, there is no significant influence on the investigated performance parameters. This clearly expands feedstock definition options prioritizing process engineering backgrounds.