Materials Requirements in Fused Filament Fabrication: A Framework for the Design of Next-Generation 3D Printable Thermoplastics and Composites

Fused filament fabrication (FFF), also known as fused deposition modeling, is the leading technology for polymer-based additive manufacturing. The simplicity, along with the cleanness, the affordability, and the multi-material capability, are some of the main advantages that have prompted this success. Nonetheless, the uptake of FFF in industry is hampered by the limited functionality of commercial filaments, that are often based on plain thermoplastics. The future growth of FFF into new markets needs a significant improvement of available materials. However, materials requirements in FFF are complicated and often mutually conflicting. Whereas heuristic approaches to materials design imply significant costs in terms of time, energy, and materials, a critical survey of the main requirements that a new material should fulfill in order to be printable and suitable for commercial adoption is still missing. In order to bridge this gap, the present paper analyzes the workflow from filament production to end-of-life disposal of printed objects, and, for each step, brings to light the governing materials properties. Wherever possible, practical guidelines are given on acceptable values. Existing lacks of knowledge are identified to direct future studies. The ultimate goal is to provide a road map to making materials development in FFF more efficient.