Influence of manufacturing process in pores, fibre distribution and mechanical properties of ASA-CF for 3D large format additive manufacturing pieces

Purpose - The purpose of this study was to evaluate parts manufactured by fused granular fabrication (FGF) using two different acrylonitrile styrene acrylate (ASA) compounds reinforced with carbon fiber (CF) and compared them with those produced by injection molding (IM). Design/methodology/approach - The difference in both ASA_CF composites is the mixing process, achieved using twin-screw extruders with different mixing shear rates. The porosity proportion and distribution, and the CF length and alignment, have been carefully quantified and compared using X-ray computerised tomography (CT). Also, the correlation with mechanical properties has been evaluated for FGF and for IM parts in both materials. Findings - Reinforcement of polymeric matrices with different fibres is a common strategy to improve the mechanical properties of 3D printing pieces, especially relevant in FGF. The manufacturing process of these composites needs to be carefully designed to optimise the structural and mechanical characteristics of the material. CT analyses show that the use of higher shear mixing rates increases the amount of pores within the polymeric pellets and produces a smaller fibre size distribution in the composites, which negatively affects the mechanical performance of the final part. Originality/value - To the best of the authors' knowledge, this is the first time that a global study of the complete fabrication process has been carried out, providing detailed information of every step of the process.