Robert Brüll

One Step Production of Bicomponent Yarns with Glass Fibre Core and Thermoplastic Sheath for Composite Applications

The film stacking method is the industrial standard for the manufacturing of fibre reinforced thermoplastic composites (FRTCs). An alternative to this is commingling thermoplastic fibres with reinforcement fibres, e. g. glass fibres, into hybrid yarns. However, the composites produced by the use of film-stacking or hybrid yarns cannot achieve an optimal impregnation of reinforcement fibres with the matrix polymer. This stens from the high melt viscosity of thermoplastics, which prevents a uniform wetting of the reinforcement fibres. Leaving some fibers is unconnected to the matrix. This leads to composite lower strength than theoretically possible. The aim of the research is the coating of a single glass filament in the glass fibre nozzle drawing process to achive a homogenous distribution of glass fibres and matrix in the final composite. The approach uses particles with a diameter from 5 to 25 μm of polyamide 12 (PA 12) which are electrostatically charged and blown at an Eglass filament in the nozzle drawing process as seen in. The particles adhering to the filament are melted by infrared heating and winded afterwards. This development will allow the homogenous distribution of fibres and the matrix in a thermoplastic composite allowing a higher fibre volume content leading to improved mechanical properties. Even though the glass filaments could be coated with PA 12, a homogenous sheath could not be achieved in this investigation. Therefore, further research will focus on an improved homogeneity by reducing the agglomeration of PA 12, using dried PA12 and enhancing the coating setup.

High strength and low weight hollow carbon fibres

Carbon fibres have strengths of 2.5 to 5 GPa in the fibre direction and an elastic modulus of 200 to 500 GPa. Carbon fibres have equal mechanical properties as steel but 20% of the weight. But the material is more expensive than steel. Therefore, they are only used in industry sectors where the benefits legitimate the high costs. The use of hollow rather than solid fibres allows an even lower weight of the components. At the same time, similar mechanical properties are achieved by the circular cross section. Carbon fibres are obtained from polyacrylonitrile fibers (PAN). These can be produced as hollow fibres. As a first step stabilization and carbonization of hollow PAN precursors is investigated to produce hollow carbon fibres.

Advanced fibre reinforced thermoplastic composites with reduced processing times by use of nanoscale fillers

The industrial standard for the manufacturing of fibre reinforced thermoplastic composites (FRTCs) is the film stacking method. An alternative to this is commingling thermoplastic fibres with reinforcing fibres into hybrid rovings. These rovings are woven into weaves and consolidated through compression moulding. This paper evaluates the effects of 5 weight percent (wt.-%) titanium dioxide (TiO2) in commingled polyamide 6 (PA6) on the cycle time during the consolidation process and the mechanical properties. A product representing the industrial standard is used as reference. In order to achieve a good comparability with this product, the film stacking process is also reproduced. Finally, the three plate types are compared regarding their consolidation, tensile and flexural strength. The results show that the hybrid roving FRTC is more consolidated, has better mechanical properties and enables shorter cycle times when compared to the film stacking process.