Hybridization of Reinforcing Nonwoven Structures Made from Recycled Carbon Fibers with Cellulosic Natural Fibers to Adjust the Mechanical and Functional Properties

Subject of the presented study is the production of wetlaid nonwovens from recycled carbon fibers hybridized with cellulosic natural fibers of kapok, flax, hemp, jute, kenaf and sisal to investigate the performance spectrum of derived consolidated fiber reinforced composites. The focus is set on a systematic comparison of the mechanical properties with various degree of hybridization. The total fiber volume content is kept constant at 30 vol.-%, whilst the share of carbon resp. natural fibers is alternated to 100, 75, 50, 25 and 0% respectively. The wetlaid nonwovens are produced via a modified paper-laying process yielding laminar textile structures with isotropic in-plane fiber orientation. Maleic anhydride-modified polypropylene is used as the matrix polymer, which is added in fiber form during nonwoven formation. The semi-finished products are consolidated via variothermal hot-pressing. In normative standard-compliant mechanical analysis, all hybridized composite materials show an increase of tensile strength as a function of increasing carbon fiber portion. Materials with a carbon fiber share of 75% show strength gains of up to 170.95% through hybridization in relation to the pure natural fiber versions. In case of bending, this behavior is not as uniform. Composites with 50% share of carbon fibers compared to versions with 75% partially show equal or even enhanced flexural performance. In this load case, a stronger influence of natural fiber inherent deviations and more complex effects of the hybridized microstructures are assumed, that need to be further investigated.