Parameters optimization of short carbon fiber-reinforced polyamide 6 printed using Big Area Additive Manufacturing (BAAM)

Big Area Additive Manufacturing (BAAM) of thermoplastic polymers is increasingly adopted for components, tooling and, especially, moulds across various industries and sectors as aerospace, automotive, energy, marine or construction due to its high productivity and low investment costs. However, geometric accuracy, layer adhesion and anisotropic properties of 3D printed parts are the main detrimental aspects for the successful implementation of this technology in the industry. As 3D printed parts need to withstand similar loads and stresses as those manufactured by traditional methods to be viable in industrial and engineering applications, enhancing mechanical properties ensures that parts do not break or deform under normal use. In this study, the effects of the main process parameters in the geometry distortion, inner defects and interfacial adhesion of 20% carbon fiber-reinforced polyamide 6 printed by pellet extrusion BAAM were determined, and the optimal process window was identified in terms of substrate deposition temperature, layer height and extruder motor rotation. With optimal parameters, the voids formed inbetween deposited beads were removed and the mechanical performance at room temperature in the z-direction compared to the bead direction was highly improved to 42% and 35% for tensile strength and modulus, respectively. It means a significant enhancement compared to the results reported by the state of the art, which show average values below 25%, and a highly notable improvement of the mechanical properties in the z-direction.