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 stems from the high melt viscosity of thermoplastics, which prevents a uniform wetting of the reinforcement fibres. Leaving some fibers unconnected to the matrix. This leads to a composite lower strength than possible in theory. The aim of the research is the coating of a single glass filament in the glass fibre nozzle drawing process to achieve 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 (PA12) which are electrostatically charged and blown at an E-glass filament in the nozzle drawing process. The particles adhering to the filament are melted by infrared heating and winded afterwards. This process allows for a homogenous distribution of fibres and matrix in the thermoplastic composite and therefore leads to a higher fibre volume content which improves mechanical properties. Even though the glass filaments could be coated with PA12, a homogenous sheath could not be achieved in this investigation. Therefore, further research will focus on an improved homogeneity by reducing the agglomeration of PA12, using dried PA12 and enhancing the coating setup.