Enhanced interlayer strength and thermal stability via dual material filament for material extrusion additive manufacturing

Abstract

The strength and toughness of material extrusion 3D printed parts is increased through the extrusion of core-sheath dual material thermoplastic filament feedstocks in which the filament core has a significantly higher glass transition temperature (Tg) than the filament sheath. Parts printed with these dual material filaments can thus be annealed after printing to increase bonding between printed layers while maintaining dimensional stability. In the present study, scaled production of a dual-material filament with a star-shaped polycarbonate core and an acrylonitrile butadiene styrene sheath is demonstrated via polymer co-extrusion. Laser powder bed fusion is used to rapidly prototype dies to achieve the desired polymer arrangement in the filament. Compared to conventional as-printed mono-material filaments, parts printed and annealed using this dual material filament show a 5-fold increase in z-direction impact toughness, and a 4-fold increase in z-direction tensile strength. Part dimensional accuracy and surface quality are excellent, even when using elevated printer nozzle temperatures, due the stabilizing effect of the polycarbonate core.