A Master of Science thesis in Mechanical Engineering by Mohamed Hassanien entitled, “A Low Cost Process for Fabricating FDM Filaments Reinforced with Inorganic Fillers”, submitted in July 2021. Thesis advisor is Dr. Maen Alkhader and thesis co-advisor Dr. Bassam Abu-Nabah. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).
Low cost desktop-sized fused deposition modelling (FDM) printers have been widely embraced by small to large scale institutions as well as individuals. Their ease of use and low cost qualified them to become an important enabling platform that enhances creativity and transforms design and modelling processes. To further enhance their utility and add another dimension to the range of possible materials that desktop FDM printers can process, multiple efforts originating from within the desktop FDM community have tried to create low cost desktop sized solutions capable of fabricating customized filaments. These attempts utilized short single screw extruders and did not have the mixing abilities provided by industrial multi-stage twin screw extruders. Therefore, low cost solutions were not effective in fabricating filaments customized with particle based fillers. This work aims to propose a process that enables low cost extruders to fabricate filaments with particle based fillers. In the proposed process, particles are heated and deposited on thermoplastic pellets that are subsequently extruded using a low cost desktop single screw extruder. Depositing the reinforcing particles on the pellets allows for minimizing the need for the mixing process that takes place in industrial extruders. To demonstrate the effectiveness of the process, PLA based filaments with two types of fillers were fabricated from commercial PLA pellets. Fillers used were Dune sand and Silicon Carbide. Dune sand was selected for its availability in the UAE and Silicon Carbide for its high stiffness and strength. Filaments with different particle weight fractions were fabricated and experimentally tested. Filaments’ stiffness and strength were measured, and their microstructure along their lateral and longitudinal directions was observed. Improvements in elastic moduli, stiffness and yield strength were recorded for both of the developed reinforced filaments. The effect of aging on tensile strength, elastic moduli and yield strength had been investigated which stems from biodegradability of PLA. Results show that the proposed process can fabricate filaments with multiple types of inorganic fillers. Produced filaments were successfully used to fabricate parts using a commercial Desktop FDM printer.