Abstract

Fused Filament Fabrication (FFF) technology is one of the most popular 3D printing processes and interest in direct manufacturing of functional parts is growing. For this reason, both techniques and feedstock materials require improvements to meet the mechanical requirements of load-bearing components. In this sense, this work is focused on the robotized FFF process of continuous carbon fiber thermoplastic composites. It includes an analysis and comparison of the developed FFF robotic 3D printing process with the conventional process, as well as the development of robotic 3D printing equipment for the manufacture of continuous fiber reinforced composites and the characterization of the printing process developed to print the new filaments based on the thermoplastic matrix and reinforced with continuous carbon fiber. The material was analysed by microscopic analysis, and the manufacturing specimens were characterized by mechanical tensile and flexural tests.

Abstract

With the recent increase in the use of additive manufacturing (AM) in more and more challenging applications, the demands on the mechanical performance and sustainability of printed parts are increasing considerably. Among the different additive manufacturing technologies, fused filament fabrication (FFF) is the most widely used for thermoplastic materials. This work focuses on comparing the behaviour of parts obtained by FFF using a bio-based polyamide (BIOPA-11) reinforced with different types of fibres: short glass fibre (GF) and a fibrillar nanoclay (SEP, sepiolite). Different composites were prepared by melt process, converted into filaments used in FFF, and characterised the final parts. The thermal and mechanical properties obtained were systematically examined as a function of printing orientation, amount and type of fibre, accompanied by X-ray tomography image analysis of the internal parts of the pieces. As expected, anisotropic properties showed improvements in Young's Modulus and tensile strength in both composites with increasing amount of reinforcement, with respect to pure biopolyamide. However, the improvements in mechanical performance of the nanocomposites were very noticeable under many conditions (composition and direction of fabrication). The research shows that this is due to the stiffening mechanism, based on the polymorphism of BIOPA, which is induced by nanometric loadings. Additionally, the internal morphology of the nanocomposite parts showed small amounts of inter-filament cavitations, while the parts obtained from the GF composites showed irregular, intra-filament cavitations. Thus, the BIOPA11 nanomaterial parts are attractive in terms of properties, weight, cost reduction, and sustainability.